| // Copyright 2022 the Vello Authors |
| // SPDX-License-Identifier: Apache-2.0 OR MIT OR Unlicense |
| |
| // Fine rasterizer. This can run in simple (just path rendering) and full |
| // modes, controllable by #define. |
| // |
| // To enable multisampled rendering, turn on both the msaa ifdef and one of msaa8 |
| // or msaa16. |
| |
| struct Tile { |
| backdrop: i32, |
| segments: u32, |
| } |
| |
| #import segment |
| #import config |
| |
| @group(0) @binding(0) |
| var<uniform> config: Config; |
| |
| @group(0) @binding(1) |
| var<storage> segments: array<Segment>; |
| |
| #import blend |
| #import ptcl |
| |
| let GRADIENT_WIDTH = 512; |
| |
| @group(0) @binding(2) |
| var<storage> ptcl: array<u32>; |
| |
| @group(0) @binding(3) |
| var<storage> info: array<u32>; |
| |
| @group(0) @binding(4) |
| var output: texture_storage_2d<rgba8unorm, write>; |
| |
| @group(0) @binding(5) |
| var gradients: texture_2d<f32>; |
| |
| @group(0) @binding(6) |
| var image_atlas: texture_2d<f32>; |
| |
| #ifdef msaa8 |
| let MASK_WIDTH = 32u; |
| let MASK_HEIGHT = 32u; |
| let SH_SAMPLES_SIZE = 512u; |
| let SAMPLE_WORDS_PER_PIXEL = 2u; |
| // This might be better in uniform, but that has 16 byte alignment |
| @group(0) @binding(7) |
| var<storage> mask_lut: array<u32, 256u>; |
| #endif |
| |
| #ifdef msaa16 |
| let MASK_WIDTH = 64u; |
| let MASK_HEIGHT = 64u; |
| let SH_SAMPLES_SIZE = 1024u; |
| let SAMPLE_WORDS_PER_PIXEL = 4u; |
| @group(0) @binding(7) |
| var<storage> mask_lut: array<u32, 2048u>; |
| #endif |
| |
| #ifdef msaa |
| let WG_SIZE = 64u; |
| var<workgroup> sh_count: array<u32, WG_SIZE>; |
| |
| // This array contains the winding number of the top left corner of each |
| // 16 pixel wide row of pixels, relative to the top left corner of the row |
| // immediately above. |
| // |
| // The values are stored packed, as 4 8-bit subwords in a 32 bit word. |
| // The values are biased signed integers, with 0x80 representing a winding |
| // number of 0, so that the range of -128 to 127 (inclusive) can be stored |
| // without carry. |
| // |
| // For the even-odd case, the same storage is repurposed, so that a single |
| // word contains 16 one-bit winding parity values packed to the word. |
| var<workgroup> sh_winding_y: array<atomic<u32>, 4u>; |
| // This array contains the winding number of the top left corner of each |
| // 16 pixel wide row of pixels, relative to the top left corner of the tile. |
| // It is expanded from sh_winding_y by inclusive prefix sum. |
| var<workgroup> sh_winding_y_prefix: array<atomic<u32>, 4u>; |
| // This array contains winding numbers of the top left corner of each |
| // pixel, relative to the top left corner of the enclosing 16 pixel |
| // wide row. |
| // |
| // During winding number accumulation, it stores a delta (winding number |
| // relative to the pixel immediately to the left), then expanded using |
| // prefix sum and reusing the same storage. |
| // |
| // The encoding and packing is the same as `sh_winding_y`. For the even-odd |
| // case, only the first 16 values are used, and each word stores packed |
| // parity values for one row of pixels. |
| var<workgroup> sh_winding: array<atomic<u32>, 64u>; |
| // This array contains winding numbers of multiple sample points within |
| // a pixel, relative to the winding number of the top left corner of the |
| // pixel. The encoding and packing is the same as `sh_winding_y`. |
| var<workgroup> sh_samples: array<atomic<u32>, SH_SAMPLES_SIZE>; |
| |
| // number of integer cells spanned by interval defined by a, b |
| fn span(a: f32, b: f32) -> u32 { |
| return u32(max(ceil(max(a, b)) - floor(min(a, b)), 1.0)); |
| } |
| |
| let SEG_SIZE = 5u; |
| |
| // See cpu_shaders/util.rs for explanation of these. |
| let ONE_MINUS_ULP: f32 = 0.99999994; |
| let ROBUST_EPSILON: f32 = 2e-7; |
| |
| // Multisampled path rendering algorithm. |
| // |
| // FIXME: This could return an array when https://github.com/gfx-rs/naga/issues/1930 is fixed. |
| // |
| // Generally, this algorithm works in an accumulation phase followed by a |
| // resolving phase, with arrays in workgroup shared memory accumulating |
| // winding number deltas as the results of edge crossings detected in the |
| // path segments. Accumulation is in two stages: first a counting stage |
| // which computes the number of pixels touched by each line segment (with |
| // each thread processing one line segment), then a stage in which the |
| // deltas are bumped. Separating these two is a partition-wide prefix sum |
| // and a binary search to assign the work to threads in a load-balanced |
| // manner. |
| // |
| // The resolving phase is also two stages: prefix sums in both x and y |
| // directions, then counting nonzero winding numbers for all samples within |
| // all pixels in the tile. |
| // |
| // A great deal of SIMD within a register (SWAR) logic is used, as there |
| // are a great many winding numbers to be computed. The interested reader |
| // is invited to study the even-odd case first, as there only one bit is |
| // needed to represent a winding number parity, thus there is a lot less |
| // bit shifting, and less shuffling altogether. |
| fn fill_path_ms(fill: CmdFill, local_id: vec2<u32>, result: ptr<function, array<f32, PIXELS_PER_THREAD>>) { |
| let even_odd = (fill.size_and_rule & 1u) != 0u; |
| // This isn't a divergent branch because the fill parameters are workgroup uniform, |
| // provably so because the ptcl buffer is bound read-only. |
| if even_odd { |
| fill_path_ms_evenodd(fill, local_id, result); |
| return; |
| } |
| let n_segs = fill.size_and_rule >> 1u; |
| let th_ix = local_id.y * (TILE_WIDTH / PIXELS_PER_THREAD) + local_id.x; |
| // Initialize winding number arrays to a winding number of 0, which is 0x80 in an |
| // 8 bit biased signed integer encoding. |
| if th_ix < 64u { |
| if th_ix < 4u { |
| atomicStore(&sh_winding_y[th_ix], 0x80808080u); |
| } |
| atomicStore(&sh_winding[th_ix], 0x80808080u); |
| } |
| let sample_count = PIXELS_PER_THREAD * SAMPLE_WORDS_PER_PIXEL; |
| for (var i = 0u; i < sample_count; i++) { |
| atomicStore(&sh_samples[th_ix * sample_count + i], 0x80808080u); |
| } |
| workgroupBarrier(); |
| let n_batch = (n_segs + (WG_SIZE - 1u)) / WG_SIZE; |
| for (var batch = 0u; batch < n_batch; batch++) { |
| let seg_ix = batch * WG_SIZE + th_ix; |
| let seg_off = fill.seg_data + seg_ix; |
| var count = 0u; |
| let slice_size = min(n_segs - batch * WG_SIZE, WG_SIZE); |
| // TODO: might save a register rewriting this in terms of limit |
| if th_ix < slice_size { |
| let segment = segments[seg_off]; |
| let xy0 = segment.point0; |
| let xy1 = segment.point1; |
| var y_edge_f = f32(TILE_HEIGHT); |
| var delta = select(-1, 1, xy1.x <= xy0.x); |
| if xy0.x == 0.0 { |
| y_edge_f = xy0.y; |
| } else if xy1.x == 0.0 { |
| y_edge_f = xy1.y; |
| } |
| // discard horizontal lines aligned to pixel grid |
| if !(xy0.y == xy1.y && xy0.y == floor(xy0.y)) { |
| count = span(xy0.x, xy1.x) + span(xy0.y, xy1.y) - 1u; |
| } |
| let y_edge = u32(ceil(y_edge_f)); |
| if y_edge < TILE_HEIGHT { |
| atomicAdd(&sh_winding_y[y_edge >> 2u], u32(delta) << ((y_edge & 3u) << 3u)); |
| } |
| } |
| // workgroup prefix sum of counts |
| sh_count[th_ix] = count; |
| let lg_n = firstLeadingBit(slice_size * 2u - 1u); |
| for (var i = 0u; i < lg_n; i++) { |
| workgroupBarrier(); |
| if th_ix >= 1u << i { |
| count += sh_count[th_ix - (1u << i)]; |
| } |
| workgroupBarrier(); |
| sh_count[th_ix] = count; |
| } |
| let total = workgroupUniformLoad(&sh_count[slice_size - 1u]); |
| for (var i = th_ix; i < total; i += WG_SIZE) { |
| // binary search to find pixel |
| var lo = 0u; |
| var hi = slice_size; |
| let goal = i; |
| while hi > lo + 1u { |
| let mid = (lo + hi) >> 1u; |
| if goal >= sh_count[mid - 1u] { |
| lo = mid; |
| } else { |
| hi = mid; |
| } |
| } |
| let el_ix = lo; |
| let last_pixel = i + 1u == sh_count[el_ix]; |
| let sub_ix = i - select(0u, sh_count[el_ix - 1u], el_ix > 0u); |
| let seg_off = fill.seg_data + batch * WG_SIZE + el_ix; |
| let segment = segments[seg_off]; |
| // Coordinates are relative to tile origin |
| let xy0_in = segment.point0; |
| let xy1_in = segment.point1; |
| let is_down = xy1_in.y >= xy0_in.y; |
| let xy0 = select(xy1_in, xy0_in, is_down); |
| let xy1 = select(xy0_in, xy1_in, is_down); |
| |
| // Set up data for line rasterization |
| // Note: this is duplicated work if total count exceeds a workgroup. |
| // One alternative is to compute it in a separate dispatch. |
| let dx = abs(xy1.x - xy0.x); |
| let dy = xy1.y - xy0.y; |
| let idxdy = 1.0 / (dx + dy); |
| var a = dx * idxdy; |
| // is_positive_slope is true for \ and | slopes, false for /. For |
| // horizontal lines, it follows the original data. |
| let is_positive_slope = xy1.x >= xy0.x; |
| let x_sign = select(-1.0, 1.0, is_positive_slope); |
| let xt0 = floor(xy0.x * x_sign); |
| let c = xy0.x * x_sign - xt0; |
| let y0i = floor(xy0.y); |
| let ytop = y0i + 1.0; |
| let b = min((dy * c + dx * (ytop - xy0.y)) * idxdy, ONE_MINUS_ULP); |
| let count_x = span(xy0.x, xy1.x) - 1u; |
| let count = count_x + span(xy0.y, xy1.y); |
| let robust_err = floor(a * (f32(count) - 1.0) + b) - f32(count_x); |
| if robust_err != 0.0 { |
| a -= ROBUST_EPSILON * sign(robust_err); |
| } |
| let x0i = i32(xt0 * x_sign + 0.5 * (x_sign - 1.0)); |
| // Use line equation to plot pixel coordinates |
| |
| let zf = a * f32(sub_ix) + b; |
| let z = floor(zf); |
| let x = x0i + i32(x_sign * z); |
| let y = i32(y0i) + i32(sub_ix) - i32(z); |
| // is_delta captures whether the line crosses the top edge of this |
| // pixel. If so, then a delta is added to `sh_winding`, followed by |
| // a prefix sum, so that a winding number delta is applied to all |
| // pixels to the right of this one. |
| var is_delta: bool; |
| // is_bump captures whether x0 crosses the left edge of this pixel. |
| var is_bump = false; |
| let zp = floor(a * f32(sub_ix - 1u) + b); |
| if sub_ix == 0u { |
| // The first (top-most) pixel in the line. It is considered to be |
| // a line crossing when it touches the top of the pixel. |
| // |
| // Note: horizontal lines aligned to the pixel grid have already |
| // been discarded. |
| is_delta = y0i == xy0.y; |
| // The pixel is counted as a left edge crossing only at the left |
| // edge of the tile (and when it is not the top left corner, |
| // using logic analogous to tiling). |
| is_bump = xy0.x == 0.0 && y0i != xy0.y; |
| } else { |
| // Pixels other than the first are a crossing at the top or on |
| // the side, based on the conservative line rasterization. When |
| // positive slope, the crossing is on the left. |
| is_delta = z == zp; |
| is_bump = is_positive_slope && !is_delta; |
| } |
| let pix_ix = u32(y) * TILE_WIDTH + u32(x); |
| if u32(x) < TILE_WIDTH - 1u && u32(y) < TILE_HEIGHT { |
| let delta_pix = pix_ix + 1u; |
| if is_delta { |
| let delta = select(u32(-1i), 1u, is_down) << ((delta_pix & 3u) << 3u); |
| atomicAdd(&sh_winding[delta_pix >> 2u], delta); |
| } |
| } |
| // Apply sample mask |
| let mask_block = u32(is_positive_slope) * (MASK_WIDTH * MASK_HEIGHT / 2u); |
| let half_height = f32(MASK_HEIGHT / 2u); |
| let mask_row = floor(min(a * half_height, half_height - 1.0)) * f32(MASK_WIDTH); |
| let mask_col = floor((zf - z) * f32(MASK_WIDTH)); |
| let mask_ix = mask_block + u32(mask_row + mask_col); |
| #ifdef msaa8 |
| var mask = mask_lut[mask_ix / 4u] >> ((mask_ix % 4u) * 8u); |
| mask &= 0xffu; |
| // Intersect with y half-plane masks |
| if sub_ix == 0u && !is_bump { |
| let mask_shift = u32(round(8.0 * (xy0.y - f32(y)))); |
| mask &= 0xffu << mask_shift; |
| } |
| if last_pixel && xy1.x != 0.0 { |
| let mask_shift = u32(round(8.0 * (xy1.y - f32(y)))); |
| mask &= ~(0xffu << mask_shift); |
| } |
| // Expand an 8 bit mask value to 8 1-bit values, packed 4 to a subword, |
| // so that two words are used to represent the result. An efficient |
| // technique is carry-less multiplication by 0b10_0000_0100_0000_1000_0001 |
| // followed by and-masking to extract bit in position 4 * k. |
| // |
| // See https://en.wikipedia.org/wiki/Carry-less_product |
| let mask_a = mask ^ (mask << 7u); |
| let mask_b = mask_a ^ (mask_a << 14u); |
| let mask0_exp = mask_b & 0x1010101u; |
| var mask0_signed = select(mask0_exp, u32(-i32(mask0_exp)), is_down); |
| let mask1_exp = (mask_b >> 4u) & 0x1010101u; |
| var mask1_signed = select(mask1_exp, u32(-i32(mask1_exp)), is_down); |
| if is_bump { |
| let bump_delta = select(u32(-0x1010101i), 0x1010101u, is_down); |
| mask0_signed += bump_delta; |
| mask1_signed += bump_delta; |
| } |
| atomicAdd(&sh_samples[pix_ix * 2u], mask0_signed); |
| atomicAdd(&sh_samples[pix_ix * 2u + 1u], mask1_signed); |
| #endif |
| #ifdef msaa16 |
| var mask = mask_lut[mask_ix / 2u] >> ((mask_ix % 2u) * 16u); |
| mask &= 0xffffu; |
| // Intersect with y half-plane masks |
| if sub_ix == 0u && !is_bump { |
| let mask_shift = u32(round(16.0 * (xy0.y - f32(y)))); |
| mask &= 0xffffu << mask_shift; |
| } |
| if last_pixel && xy1.x != 0.0 { |
| let mask_shift = u32(round(16.0 * (xy1.y - f32(y)))); |
| mask &= ~(0xffffu << mask_shift); |
| } |
| // Similar logic as above, only a 16 bit mask is divided into |
| // two 8 bit halves first, then each is expanded as above. |
| // Mask is 0bABCD_EFGH_IJKL_MNOP. Expand to 4 32 bit words |
| // mask0_exp will be 0b0000_000M_0000_000N_0000_000O_0000_000P |
| // mask3_exp will be 0b0000_000A_0000_000B_0000_000C_0000_000D |
| let mask0 = mask & 0xffu; |
| // mask0_a = 0b0IJK_LMNO_*JKL_MNOP |
| let mask0_a = mask0 ^ (mask0 << 7u); |
| // mask0_b = 0b000I_JKLM_NO*J_KLMN_O*K_LMNO_*JKL_MNOP |
| // ^ ^ ^ ^ ^ ^ ^ ^ |
| let mask0_b = mask0_a ^ (mask0_a << 14u); |
| let mask0_exp = mask0_b & 0x1010101u; |
| var mask0_signed = select(mask0_exp, u32(-i32(mask0_exp)), is_down); |
| let mask1_exp = (mask0_b >> 4u) & 0x1010101u; |
| var mask1_signed = select(mask1_exp, u32(-i32(mask1_exp)), is_down); |
| let mask1 = (mask >> 8u) & 0xffu; |
| let mask1_a = mask1 ^ (mask1 << 7u); |
| // mask1_a = 0b0ABC_DEFG_*BCD_EFGH |
| let mask1_b = mask1_a ^ (mask1_a << 14u); |
| // mask1_b = 0b000A_BCDE_FG*B_CDEF_G*C_DEFG_*BCD_EFGH |
| let mask2_exp = mask1_b & 0x1010101u; |
| var mask2_signed = select(mask2_exp, u32(-i32(mask2_exp)), is_down); |
| let mask3_exp = (mask1_b >> 4u) & 0x1010101u; |
| var mask3_signed = select(mask3_exp, u32(-i32(mask3_exp)), is_down); |
| if is_bump { |
| let bump_delta = select(u32(-0x1010101i), 0x1010101u, is_down); |
| mask0_signed += bump_delta; |
| mask1_signed += bump_delta; |
| mask2_signed += bump_delta; |
| mask3_signed += bump_delta; |
| } |
| atomicAdd(&sh_samples[pix_ix * 4u], mask0_signed); |
| atomicAdd(&sh_samples[pix_ix * 4u + 1u], mask1_signed); |
| atomicAdd(&sh_samples[pix_ix * 4u + 2u], mask2_signed); |
| atomicAdd(&sh_samples[pix_ix * 4u + 3u], mask3_signed); |
| #endif |
| } |
| workgroupBarrier(); |
| } |
| var area: array<f32, PIXELS_PER_THREAD>; |
| let major = (th_ix * PIXELS_PER_THREAD) >> 2u; |
| var packed_w = atomicLoad(&sh_winding[major]); |
| // Compute prefix sums of both `sh_winding` and `sh_winding_y`. Both |
| // use the same technique. First, a per-word prefix sum is computed |
| // of the 4 subwords within each word. The last subword is the sum |
| // (reduction) of that group of 4 values, and is stored to shared |
| // memory for broadcast to other threads. Then each thread computes |
| // the prefix by adding the preceding reduced values. |
| // |
| // Addition of 2 biased signed values is accomplished by adding the |
| // values, then subtracting the bias. |
| packed_w += (packed_w - 0x808080u) << 8u; |
| packed_w += (packed_w - 0x8080u) << 16u; |
| var packed_y = atomicLoad(&sh_winding_y[local_id.y >> 2u]); |
| packed_y += (packed_y - 0x808080u) << 8u; |
| packed_y += (packed_y - 0x8080u) << 16u; |
| var wind_y = (packed_y >> ((local_id.y & 3u) << 3u)) - 0x80u; |
| if (local_id.y & 3u) == 3u && local_id.x == 0u { |
| let prefix_y = wind_y; |
| atomicStore(&sh_winding_y_prefix[local_id.y >> 2u], prefix_y); |
| } |
| let prefix_x = ((packed_w >> 24u) - 0x80u) * 0x1010101u; |
| // reuse sh_winding to store prefix as well |
| atomicStore(&sh_winding[major], prefix_x); |
| workgroupBarrier(); |
| for (var i = (major & ~3u); i < major; i++) { |
| packed_w += atomicLoad(&sh_winding[i]); |
| } |
| // packed_w now contains the winding numbers for a slice of 4 pixels, |
| // each relative to the top left of the row. |
| for (var i = 0u; i < (local_id.y >> 2u); i++) { |
| wind_y += atomicLoad(&sh_winding_y_prefix[i]); |
| } |
| // wind_y now contains the winding number of the top left of the row of |
| // pixels relative to the top left of the tile. Note that this is actually |
| // a signed quantity stored without bias. |
| |
| // The winding number of a sample point is the sum of four levels of |
| // hierarchy: |
| // * The winding number of the top left of the tile (backdrop) |
| // * The winding number of the pixel row relative to tile (wind_y) |
| // * The winding number of the pixel relative to row (packed_w) |
| // * The winding number of the sample relative to pixel (sh_samples) |
| // |
| // Conceptually, we want to compute each of these total winding numbers |
| // for each sample within a pixel, then count the number that are non-zero. |
| // However, we apply a shortcut, partly to make the computation more |
| // efficient, and partly to avoid overflow of intermediate results. |
| // |
| // Here's the technique that's used. The `expected_zero` value contains |
| // the *negation* of the sum of the first three levels of the hierarchy. |
| // Thus, `sample - expected` is zero when the sum of all levels in the |
| // hierarchy is zero, and this is true when `sample = expected`. We |
| // compute this using SWAR techniques as follows: we compute the xor of |
| // all bits of `expected` (repeated to all subwords) against the packed |
| // samples, then the or-reduction of the bits within each subword. This |
| // value is 1 when the values are unequal, thus the sum is nonzero, and |
| // 0 when the sum is zero. These bits are then masked and counted. |
| |
| for (var i = 0u; i < PIXELS_PER_THREAD; i++) { |
| let pix_ix = th_ix * PIXELS_PER_THREAD + i; |
| let minor = i; // assumes PIXELS_PER_THREAD == 4 |
| let expected_zero = (((packed_w >> (minor * 8u)) + wind_y) & 0xffu) - u32(fill.backdrop); |
| // When the expected_zero value exceeds the range of what can be stored |
| // in a (biased) signed integer, then there is no sample value that can |
| // be equal to the expected value, thus all resulting bits are 1. |
| if expected_zero >= 256u { |
| area[i] = 1.0; |
| } else { |
| #ifdef msaa8 |
| let samples0 = atomicLoad(&sh_samples[pix_ix * 2u]); |
| let samples1 = atomicLoad(&sh_samples[pix_ix * 2u + 1u]); |
| let xored0 = (expected_zero * 0x1010101u) ^ samples0; |
| let xored0_2 = xored0 | (xored0 * 2u); |
| let xored1 = (expected_zero * 0x1010101u) ^ samples1; |
| let xored1_2 = xored1 | (xored1 >> 1u); |
| // xored2 contains 2-reductions from each word, interleaved |
| let xored2 = (xored0_2 & 0xAAAAAAAAu) | (xored1_2 & 0x55555555u); |
| // bits 4 * k + 2 and 4 * k + 3 contain 4-reductions |
| let xored4 = xored2 | (xored2 * 4u); |
| // bits 8 * k + 6 and 8 * k + 7 contain 8-reductions |
| let xored8 = xored4 | (xored4 * 16u); |
| area[i] = f32(countOneBits(xored8 & 0xC0C0C0C0u)) * 0.125; |
| #endif |
| #ifdef msaa16 |
| let samples0 = atomicLoad(&sh_samples[pix_ix * 4u]); |
| let samples1 = atomicLoad(&sh_samples[pix_ix * 4u + 1u]); |
| let samples2 = atomicLoad(&sh_samples[pix_ix * 4u + 2u]); |
| let samples3 = atomicLoad(&sh_samples[pix_ix * 4u + 3u]); |
| let xored0 = (expected_zero * 0x1010101u) ^ samples0; |
| let xored0_2 = xored0 | (xored0 * 2u); |
| let xored1 = (expected_zero * 0x1010101u) ^ samples1; |
| let xored1_2 = xored1 | (xored1 >> 1u); |
| // xored01 contains 2-reductions from words 0 and 1, interleaved |
| let xored01 = (xored0_2 & 0xAAAAAAAAu) | (xored1_2 & 0x55555555u); |
| // bits 4 * k + 2 and 4 * k + 3 contain 4-reductions |
| let xored01_4 = xored01 | (xored01 * 4u); |
| let xored2 = (expected_zero * 0x1010101u) ^ samples2; |
| let xored2_2 = xored2 | (xored2 * 2u); |
| let xored3 = (expected_zero * 0x1010101u) ^ samples3; |
| let xored3_2 = xored3 | (xored3 >> 1u); |
| // xored23 contains 2-reductions from words 2 and 3, interleaved |
| let xored23 = (xored2_2 & 0xAAAAAAAAu) | (xored3_2 & 0x55555555u); |
| // bits 4 * k and 4 * k + 1 contain 4-reductions |
| let xored23_4 = xored23 | (xored23 >> 2u); |
| // each bit is a 4-reduction, with values from all 4 words |
| let xored4 = (xored01_4 & 0xCCCCCCCCu) | (xored23_4 & 0x33333333u); |
| // bits 8 * k + {4, 5, 6, 7} contain 8-reductions |
| let xored8 = xored4 | (xored4 * 16u); |
| area[i] = f32(countOneBits(xored8 & 0xF0F0F0F0u)) * 0.0625; |
| #endif |
| } |
| } |
| *result = area; |
| } |
| |
| // Path rendering specialized to the even-odd rule. |
| // |
| // This proceeds very much the same as `fill_path_ms`, but is simpler because |
| // all winding numbers can be represented in one bit. Formally, addition is |
| // modulo 2, or, equivalently, winding numbers are elements of GF(2). One |
| // simplification is that we don't need to track the direction of crossings, |
| // as both have the same effect on winding number. |
| // |
| // TODO: factor some logic out to reduce code duplication. |
| fn fill_path_ms_evenodd(fill: CmdFill, local_id: vec2<u32>, result: ptr<function, array<f32, PIXELS_PER_THREAD>>) { |
| let n_segs = fill.size_and_rule >> 1u; |
| let th_ix = local_id.y * (TILE_WIDTH / PIXELS_PER_THREAD) + local_id.x; |
| if th_ix < TILE_HEIGHT { |
| if th_ix == 0u { |
| atomicStore(&sh_winding_y[th_ix], 0u); |
| } |
| atomicStore(&sh_winding[th_ix], 0u); |
| } |
| let sample_count = PIXELS_PER_THREAD; |
| for (var i = 0u; i < sample_count; i++) { |
| atomicStore(&sh_samples[th_ix * sample_count + i], 0u); |
| } |
| workgroupBarrier(); |
| let n_batch = (n_segs + (WG_SIZE - 1u)) / WG_SIZE; |
| for (var batch = 0u; batch < n_batch; batch++) { |
| let seg_ix = batch * WG_SIZE + th_ix; |
| let seg_off = fill.seg_data + seg_ix; |
| var count = 0u; |
| let slice_size = min(n_segs - batch * WG_SIZE, WG_SIZE); |
| // TODO: might save a register rewriting this in terms of limit |
| if th_ix < slice_size { |
| let segment = segments[seg_off]; |
| // Coordinates are relative to tile origin |
| let xy0 = segment.point0; |
| let xy1 = segment.point1; |
| var y_edge_f = f32(TILE_HEIGHT); |
| if xy0.x == 0.0 { |
| y_edge_f = xy0.y; |
| } else if xy1.x == 0.0 { |
| y_edge_f = xy1.y; |
| } |
| // discard horizontal lines aligned to pixel grid |
| if !(xy0.y == xy1.y && xy0.y == floor(xy0.y)) { |
| count = span(xy0.x, xy1.x) + span(xy0.y, xy1.y) - 1u; |
| } |
| let y_edge = u32(ceil(y_edge_f)); |
| if y_edge < TILE_HEIGHT { |
| atomicXor(&sh_winding_y[0], 1u << y_edge); |
| } |
| } |
| // workgroup prefix sum of counts |
| sh_count[th_ix] = count; |
| let lg_n = firstLeadingBit(slice_size * 2u - 1u); |
| for (var i = 0u; i < lg_n; i++) { |
| workgroupBarrier(); |
| if th_ix >= 1u << i { |
| count += sh_count[th_ix - (1u << i)]; |
| } |
| workgroupBarrier(); |
| sh_count[th_ix] = count; |
| } |
| let total = workgroupUniformLoad(&sh_count[slice_size - 1u]); |
| for (var i = th_ix; i < total; i += WG_SIZE) { |
| // binary search to find pixel |
| var lo = 0u; |
| var hi = slice_size; |
| let goal = i; |
| while hi > lo + 1u { |
| let mid = (lo + hi) >> 1u; |
| if goal >= sh_count[mid - 1u] { |
| lo = mid; |
| } else { |
| hi = mid; |
| } |
| } |
| let el_ix = lo; |
| let last_pixel = i + 1u == sh_count[el_ix]; |
| let sub_ix = i - select(0u, sh_count[el_ix - 1u], el_ix > 0u); |
| let seg_off = fill.seg_data + batch * WG_SIZE + el_ix; |
| let segment = segments[seg_off]; |
| let xy0_in = segment.point0; |
| let xy1_in = segment.point1; |
| let is_down = xy1_in.y >= xy0_in.y; |
| let xy0 = select(xy1_in, xy0_in, is_down); |
| let xy1 = select(xy0_in, xy1_in, is_down); |
| |
| // Set up data for line rasterization |
| // Note: this is duplicated work if total count exceeds a workgroup. |
| // One alternative is to compute it in a separate dispatch. |
| let dx = abs(xy1.x - xy0.x); |
| let dy = xy1.y - xy0.y; |
| let idxdy = 1.0 / (dx + dy); |
| var a = dx * idxdy; |
| let is_positive_slope = xy1.x >= xy0.x; |
| let x_sign = select(-1.0, 1.0, is_positive_slope); |
| let xt0 = floor(xy0.x * x_sign); |
| let c = xy0.x * x_sign - xt0; |
| let y0i = floor(xy0.y); |
| let ytop = y0i + 1.0; |
| let b = min((dy * c + dx * (ytop - xy0.y)) * idxdy, ONE_MINUS_ULP); |
| let count_x = span(xy0.x, xy1.x) - 1u; |
| let count = count_x + span(xy0.y, xy1.y); |
| let robust_err = floor(a * (f32(count) - 1.0) + b) - f32(count_x); |
| if robust_err != 0.0 { |
| a -= ROBUST_EPSILON * sign(robust_err); |
| } |
| let x0i = i32(xt0 * x_sign + 0.5 * (x_sign - 1.0)); |
| // Use line equation to plot pixel coordinates |
| |
| let zf = a * f32(sub_ix) + b; |
| let z = floor(zf); |
| let x = x0i + i32(x_sign * z); |
| let y = i32(y0i) + i32(sub_ix) - i32(z); |
| var is_delta: bool; |
| // See comments in nonzero case. |
| var is_bump = false; |
| let zp = floor(a * f32(sub_ix - 1u) + b); |
| if sub_ix == 0u { |
| is_delta = y0i == xy0.y; |
| is_bump = xy0.x == 0.0; |
| } else { |
| is_delta = z == zp; |
| is_bump = is_positive_slope && !is_delta; |
| } |
| if u32(x) < TILE_WIDTH - 1u && u32(y) < TILE_HEIGHT { |
| if is_delta { |
| atomicXor(&sh_winding[y], 2u << u32(x)); |
| } |
| } |
| // Apply sample mask |
| let mask_block = u32(is_positive_slope) * (MASK_WIDTH * MASK_HEIGHT / 2u); |
| let half_height = f32(MASK_HEIGHT / 2u); |
| let mask_row = floor(min(a * half_height, half_height - 1.0)) * f32(MASK_WIDTH); |
| let mask_col = floor((zf - z) * f32(MASK_WIDTH)); |
| let mask_ix = mask_block + u32(mask_row + mask_col); |
| let pix_ix = u32(y) * TILE_WIDTH + u32(x); |
| #ifdef msaa8 |
| var mask = mask_lut[mask_ix / 4u] >> ((mask_ix % 4u) * 8u); |
| mask &= 0xffu; |
| // Intersect with y half-plane masks |
| if sub_ix == 0u && !is_bump { |
| let mask_shift = u32(round(8.0 * (xy0.y - f32(y)))); |
| mask &= 0xffu << mask_shift; |
| } |
| if last_pixel && xy1.x != 0.0 { |
| let mask_shift = u32(round(8.0 * (xy1.y - f32(y)))); |
| mask &= ~(0xffu << mask_shift); |
| } |
| if is_bump { |
| mask ^= 0xffu; |
| } |
| atomicXor(&sh_samples[pix_ix], mask); |
| #endif |
| #ifdef msaa16 |
| var mask = mask_lut[mask_ix / 2u] >> ((mask_ix % 2u) * 16u); |
| mask &= 0xffffu; |
| // Intersect with y half-plane masks |
| if sub_ix == 0u && !is_bump { |
| let mask_shift = u32(round(16.0 * (xy0.y - f32(y)))); |
| mask &= 0xffffu << mask_shift; |
| } |
| if last_pixel && xy1.x != 0.0 { |
| let mask_shift = u32(round(16.0 * (xy1.y - f32(y)))); |
| mask &= ~(0xffffu << mask_shift); |
| } |
| if is_bump { |
| mask ^= 0xffffu; |
| } |
| atomicXor(&sh_samples[pix_ix], mask); |
| #endif |
| } |
| workgroupBarrier(); |
| } |
| var area: array<f32, PIXELS_PER_THREAD>; |
| var scan_x = atomicLoad(&sh_winding[local_id.y]); |
| // prefix sum over GF(2) is equivalent to carry-less multiplication |
| // by 0xFFFF |
| scan_x ^= scan_x << 1u; |
| scan_x ^= scan_x << 2u; |
| scan_x ^= scan_x << 4u; |
| scan_x ^= scan_x << 8u; |
| // scan_x contains the winding number parity for all pixels in the row |
| var scan_y = atomicLoad(&sh_winding_y[0]); |
| scan_y ^= scan_y << 1u; |
| scan_y ^= scan_y << 2u; |
| scan_y ^= scan_y << 4u; |
| scan_y ^= scan_y << 8u; |
| // winding number parity for the row of pixels is in the LSB of row_parity |
| let row_parity = (scan_y >> local_id.y) ^ u32(fill.backdrop); |
| |
| for (var i = 0u; i < PIXELS_PER_THREAD; i++) { |
| let pix_ix = th_ix * PIXELS_PER_THREAD + i; |
| let samples = atomicLoad(&sh_samples[pix_ix]); |
| let pix_parity = row_parity ^ (scan_x >> (pix_ix % TILE_WIDTH)); |
| // The LSB of pix_parity contains the sum of the first three levels |
| // of the hierarchy, thus the absolute winding number of the top left |
| // of the pixel. |
| let pix_mask = u32(-i32(pix_parity & 1u)); |
| // pix_mask is pix_party broadcast to all bits in the word. |
| #ifdef msaa8 |
| area[i] = f32(countOneBits((samples ^ pix_mask) & 0xffu)) * 0.125; |
| #endif |
| #ifdef msaa16 |
| area[i] = f32(countOneBits((samples ^ pix_mask) & 0xffffu)) * 0.0625; |
| #endif |
| } |
| *result = area; |
| } |
| #endif |
| |
| fn read_fill(cmd_ix: u32) -> CmdFill { |
| let size_and_rule = ptcl[cmd_ix + 1u]; |
| let seg_data = ptcl[cmd_ix + 2u]; |
| let backdrop = i32(ptcl[cmd_ix + 3u]); |
| return CmdFill(size_and_rule, seg_data, backdrop); |
| } |
| |
| fn read_color(cmd_ix: u32) -> CmdColor { |
| let rgba_color = ptcl[cmd_ix + 1u]; |
| return CmdColor(rgba_color); |
| } |
| |
| fn read_lin_grad(cmd_ix: u32) -> CmdLinGrad { |
| let index_mode = ptcl[cmd_ix + 1u]; |
| let index = index_mode >> 2u; |
| let extend_mode = index_mode & 0x3u; |
| let info_offset = ptcl[cmd_ix + 2u]; |
| let line_x = bitcast<f32>(info[info_offset]); |
| let line_y = bitcast<f32>(info[info_offset + 1u]); |
| let line_c = bitcast<f32>(info[info_offset + 2u]); |
| return CmdLinGrad(index, extend_mode, line_x, line_y, line_c); |
| } |
| |
| fn read_rad_grad(cmd_ix: u32) -> CmdRadGrad { |
| let index_mode = ptcl[cmd_ix + 1u]; |
| let index = index_mode >> 2u; |
| let extend_mode = index_mode & 0x3u; |
| let info_offset = ptcl[cmd_ix + 2u]; |
| let m0 = bitcast<f32>(info[info_offset]); |
| let m1 = bitcast<f32>(info[info_offset + 1u]); |
| let m2 = bitcast<f32>(info[info_offset + 2u]); |
| let m3 = bitcast<f32>(info[info_offset + 3u]); |
| let matrx = vec4(m0, m1, m2, m3); |
| let xlat = vec2(bitcast<f32>(info[info_offset + 4u]), bitcast<f32>(info[info_offset + 5u])); |
| let focal_x = bitcast<f32>(info[info_offset + 6u]); |
| let radius = bitcast<f32>(info[info_offset + 7u]); |
| let flags_kind = info[info_offset + 8u]; |
| let flags = flags_kind >> 3u; |
| let kind = flags_kind & 0x7u; |
| return CmdRadGrad(index, extend_mode, matrx, xlat, focal_x, radius, kind, flags); |
| } |
| |
| fn read_sweep_grad(cmd_ix: u32) -> CmdSweepGrad { |
| let index_mode = ptcl[cmd_ix + 1u]; |
| let index = index_mode >> 2u; |
| let extend_mode = index_mode & 0x3u; |
| let info_offset = ptcl[cmd_ix + 2u]; |
| let m0 = bitcast<f32>(info[info_offset]); |
| let m1 = bitcast<f32>(info[info_offset + 1u]); |
| let m2 = bitcast<f32>(info[info_offset + 2u]); |
| let m3 = bitcast<f32>(info[info_offset + 3u]); |
| let matrx = vec4(m0, m1, m2, m3); |
| let xlat = vec2(bitcast<f32>(info[info_offset + 4u]), bitcast<f32>(info[info_offset + 5u])); |
| let t0 = bitcast<f32>(info[info_offset + 6u]); |
| let t1 = bitcast<f32>(info[info_offset + 7u]); |
| return CmdSweepGrad(index, extend_mode, matrx, xlat, t0, t1); |
| } |
| |
| fn read_image(cmd_ix: u32) -> CmdImage { |
| let info_offset = ptcl[cmd_ix + 1u]; |
| let m0 = bitcast<f32>(info[info_offset]); |
| let m1 = bitcast<f32>(info[info_offset + 1u]); |
| let m2 = bitcast<f32>(info[info_offset + 2u]); |
| let m3 = bitcast<f32>(info[info_offset + 3u]); |
| let matrx = vec4(m0, m1, m2, m3); |
| let xlat = vec2(bitcast<f32>(info[info_offset + 4u]), bitcast<f32>(info[info_offset + 5u])); |
| let xy = info[info_offset + 6u]; |
| let width_height = info[info_offset + 7u]; |
| // The following are not intended to be bitcasts |
| let x = f32(xy >> 16u); |
| let y = f32(xy & 0xffffu); |
| let width = f32(width_height >> 16u); |
| let height = f32(width_height & 0xffffu); |
| return CmdImage(matrx, xlat, vec2(x, y), vec2(width, height)); |
| } |
| |
| fn read_end_clip(cmd_ix: u32) -> CmdEndClip { |
| let blend = ptcl[cmd_ix + 1u]; |
| let alpha = bitcast<f32>(ptcl[cmd_ix + 2u]); |
| return CmdEndClip(blend, alpha); |
| } |
| |
| fn extend_mode(t: f32, mode: u32) -> f32 { |
| let EXTEND_PAD = 0u; |
| let EXTEND_REPEAT = 1u; |
| let EXTEND_REFLECT = 2u; |
| switch mode { |
| // EXTEND_PAD |
| case 0u: { |
| return clamp(t, 0.0, 1.0); |
| } |
| // EXTEND_REPEAT |
| case 1u: { |
| return fract(t); |
| } |
| // EXTEND_REFLECT |
| default: { |
| return abs(t - 2.0 * round(0.5 * t)); |
| } |
| } |
| } |
| |
| let PIXELS_PER_THREAD = 4u; |
| |
| // Analytic area antialiasing. |
| // |
| // This is currently dead code if msaa is enabled, but it would be fairly straightforward |
| // to wire this so it's a dynamic choice (even per-path). |
| // |
| // FIXME: This should return an array when https://github.com/gfx-rs/naga/issues/1930 is fixed. |
| fn fill_path(fill: CmdFill, xy: vec2<f32>, result: ptr<function, array<f32, PIXELS_PER_THREAD>>) { |
| let n_segs = fill.size_and_rule >> 1u; |
| let even_odd = (fill.size_and_rule & 1u) != 0u; |
| var area: array<f32, PIXELS_PER_THREAD>; |
| let backdrop_f = f32(fill.backdrop); |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| area[i] = backdrop_f; |
| } |
| for (var i = 0u; i < n_segs; i++) { |
| let seg_off = fill.seg_data + i; |
| let segment = segments[seg_off]; |
| let y = segment.point0.y - xy.y; |
| let delta = segment.point1 - segment.point0; |
| let y0 = clamp(y, 0.0, 1.0); |
| let y1 = clamp(y + delta.y, 0.0, 1.0); |
| let dy = y0 - y1; |
| if dy != 0.0 { |
| let vec_y_recip = 1.0 / delta.y; |
| let t0 = (y0 - y) * vec_y_recip; |
| let t1 = (y1 - y) * vec_y_recip; |
| let startx = segment.point0.x - xy.x; |
| let x0 = startx + t0 * delta.x; |
| let x1 = startx + t1 * delta.x; |
| let xmin0 = min(x0, x1); |
| let xmax0 = max(x0, x1); |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| let i_f = f32(i); |
| let xmin = min(xmin0 - i_f, 1.0) - 1.0e-6; |
| let xmax = xmax0 - i_f; |
| let b = min(xmax, 1.0); |
| let c = max(b, 0.0); |
| let d = max(xmin, 0.0); |
| let a = (b + 0.5 * (d * d - c * c) - xmin) / (xmax - xmin); |
| area[i] += a * dy; |
| } |
| } |
| let y_edge = sign(delta.x) * clamp(xy.y - segment.y_edge + 1.0, 0.0, 1.0); |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| area[i] += y_edge; |
| } |
| } |
| if even_odd { |
| // even-odd winding rule |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| let a = area[i]; |
| area[i] = abs(a - 2.0 * round(0.5 * a)); |
| } |
| } else { |
| // non-zero winding rule |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| area[i] = min(abs(area[i]), 1.0); |
| } |
| } |
| *result = area; |
| } |
| |
| // The X size should be 16 / PIXELS_PER_THREAD |
| @compute @workgroup_size(4, 16) |
| fn main( |
| @builtin(global_invocation_id) global_id: vec3<u32>, |
| @builtin(local_invocation_id) local_id: vec3<u32>, |
| @builtin(workgroup_id) wg_id: vec3<u32>, |
| ) { |
| let tile_ix = wg_id.y * config.width_in_tiles + wg_id.x; |
| let xy = vec2(f32(global_id.x * PIXELS_PER_THREAD), f32(global_id.y)); |
| let local_xy = vec2(f32(local_id.x * PIXELS_PER_THREAD), f32(local_id.y)); |
| #ifdef full |
| var rgba: array<vec4<f32>, PIXELS_PER_THREAD>; |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| rgba[i] = unpack4x8unorm(config.base_color).wzyx; |
| } |
| var blend_stack: array<array<u32, PIXELS_PER_THREAD>, BLEND_STACK_SPLIT>; |
| var clip_depth = 0u; |
| var area: array<f32, PIXELS_PER_THREAD>; |
| var cmd_ix = tile_ix * PTCL_INITIAL_ALLOC; |
| let blend_offset = ptcl[cmd_ix]; |
| cmd_ix += 1u; |
| // main interpretation loop |
| while true { |
| let tag = ptcl[cmd_ix]; |
| if tag == CMD_END { |
| break; |
| } |
| switch tag { |
| // CMD_FILL |
| case 1u: { |
| let fill = read_fill(cmd_ix); |
| #ifdef msaa |
| fill_path_ms(fill, local_id.xy, &area); |
| #else |
| fill_path(fill, local_xy, &area); |
| #endif |
| cmd_ix += 4u; |
| } |
| // CMD_STROKE |
| case 2u: { |
| // Stroking in fine rasterization is disabled, as strokes will be expanded |
| // to fills earlier in the pipeline. This implementation is a stub, just to |
| // keep the shader from crashing. |
| for (var i = 0u; i < PIXELS_PER_THREAD; i++) { |
| area[i] = 0.0; |
| } |
| cmd_ix += 3u; |
| } |
| // CMD_SOLID |
| case 3u: { |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| area[i] = 1.0; |
| } |
| cmd_ix += 1u; |
| } |
| // CMD_COLOR |
| case 5u: { |
| let color = read_color(cmd_ix); |
| let fg = unpack4x8unorm(color.rgba_color).wzyx; |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| let fg_i = fg * area[i]; |
| rgba[i] = rgba[i] * (1.0 - fg_i.a) + fg_i; |
| } |
| cmd_ix += 2u; |
| } |
| // CMD_LIN_GRAD |
| case 6u: { |
| let lin = read_lin_grad(cmd_ix); |
| let d = lin.line_x * xy.x + lin.line_y * xy.y + lin.line_c; |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| let my_d = d + lin.line_x * f32(i); |
| let x = i32(round(extend_mode(my_d, lin.extend_mode) * f32(GRADIENT_WIDTH - 1))); |
| let fg_rgba = textureLoad(gradients, vec2(x, i32(lin.index)), 0); |
| let fg_i = fg_rgba * area[i]; |
| rgba[i] = rgba[i] * (1.0 - fg_i.a) + fg_i; |
| } |
| cmd_ix += 3u; |
| } |
| // CMD_RAD_GRAD |
| case 7u: { |
| let rad = read_rad_grad(cmd_ix); |
| let focal_x = rad.focal_x; |
| let radius = rad.radius; |
| let is_strip = rad.kind == RAD_GRAD_KIND_STRIP; |
| let is_circular = rad.kind == RAD_GRAD_KIND_CIRCULAR; |
| let is_focal_on_circle = rad.kind == RAD_GRAD_KIND_FOCAL_ON_CIRCLE; |
| let is_swapped = (rad.flags & RAD_GRAD_SWAPPED) != 0u; |
| let r1_recip = select(1.0 / radius, 0.0, is_circular); |
| let less_scale = select(1.0, -1.0, is_swapped || (1.0 - focal_x) < 0.0); |
| let t_sign = sign(1.0 - focal_x); |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| let my_xy = vec2(xy.x + f32(i), xy.y); |
| let local_xy = rad.matrx.xy * my_xy.x + rad.matrx.zw * my_xy.y + rad.xlat; |
| let x = local_xy.x; |
| let y = local_xy.y; |
| let xx = x * x; |
| let yy = y * y; |
| var t = 0.0; |
| var is_valid = true; |
| if is_strip { |
| let a = radius - yy; |
| t = sqrt(a) + x; |
| is_valid = a >= 0.0; |
| } else if is_focal_on_circle { |
| t = (xx + yy) / x; |
| is_valid = t >= 0.0 && x != 0.0; |
| } else if radius > 1.0 { |
| t = sqrt(xx + yy) - x * r1_recip; |
| } else { // radius < 1.0 |
| let a = xx - yy; |
| t = less_scale * sqrt(a) - x * r1_recip; |
| is_valid = a >= 0.0 && t >= 0.0; |
| } |
| if is_valid { |
| t = extend_mode(focal_x + t_sign * t, rad.extend_mode); |
| t = select(t, 1.0 - t, is_swapped); |
| let x = i32(round(t * f32(GRADIENT_WIDTH - 1))); |
| let fg_rgba = textureLoad(gradients, vec2(x, i32(rad.index)), 0); |
| let fg_i = fg_rgba * area[i]; |
| rgba[i] = rgba[i] * (1.0 - fg_i.a) + fg_i; |
| } |
| } |
| cmd_ix += 3u; |
| } |
| // CMD_SWEEP_GRAD |
| case 8u: { |
| let sweep = read_sweep_grad(cmd_ix); |
| let scale = 1.0 / (sweep.t1 - sweep.t0); |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| let my_xy = vec2(xy.x + f32(i), xy.y); |
| let local_xy = sweep.matrx.xy * my_xy.x + sweep.matrx.zw * my_xy.y + sweep.xlat; |
| let x = local_xy.x; |
| let y = local_xy.y; |
| // xy_to_unit_angle from Skia: |
| // See <https://github.com/google/skia/blob/30bba741989865c157c7a997a0caebe94921276b/src/opts/SkRasterPipeline_opts.h#L5859> |
| let xabs = abs(x); |
| let yabs = abs(y); |
| let slope = min(xabs, yabs) / max(xabs, yabs); |
| let s = slope * slope; |
| // again, from Skia: |
| // Use a 7th degree polynomial to approximate atan. |
| // This was generated using sollya.gforge.inria.fr. |
| // A float optimized polynomial was generated using the following command. |
| // P1 = fpminimax((1/(2*Pi))*atan(x),[|1,3,5,7|],[|24...|],[2^(-40),1],relative); |
| var phi = slope * (0.15912117063999176025390625f + s * (-5.185396969318389892578125e-2f + s * (2.476101927459239959716796875e-2f + s * (-7.0547382347285747528076171875e-3f)))); |
| phi = select(phi, 1.0 / 4.0 - phi, xabs < yabs); |
| phi = select(phi, 1.0 / 2.0 - phi, x < 0.0); |
| phi = select(phi, 1.0 - phi, y < 0.0); |
| phi = select(phi, 0.0, phi != phi); // check for NaN |
| phi = (phi - sweep.t0) * scale; |
| let t = extend_mode(phi, sweep.extend_mode); |
| let ramp_x = i32(round(t * f32(GRADIENT_WIDTH - 1))); |
| let fg_rgba = textureLoad(gradients, vec2(ramp_x, i32(sweep.index)), 0); |
| let fg_i = fg_rgba * area[i]; |
| rgba[i] = rgba[i] * (1.0 - fg_i.a) + fg_i; |
| } |
| cmd_ix += 3u; |
| } |
| // CMD_IMAGE |
| case 9u: { |
| let image = read_image(cmd_ix); |
| let atlas_extents = image.atlas_offset + image.extents; |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| let my_xy = vec2(xy.x + f32(i), xy.y); |
| let atlas_uv = image.matrx.xy * my_xy.x + image.matrx.zw * my_xy.y + image.xlat + image.atlas_offset; |
| // This currently clips to the image bounds. TODO: extend modes |
| if all(atlas_uv < atlas_extents) && area[i] != 0.0 { |
| let uv_quad = vec4(max(floor(atlas_uv), image.atlas_offset), min(ceil(atlas_uv), atlas_extents)); |
| let uv_frac = fract(atlas_uv); |
| let a = premul_alpha(textureLoad(image_atlas, vec2<i32>(uv_quad.xy), 0)); |
| let b = premul_alpha(textureLoad(image_atlas, vec2<i32>(uv_quad.xw), 0)); |
| let c = premul_alpha(textureLoad(image_atlas, vec2<i32>(uv_quad.zy), 0)); |
| let d = premul_alpha(textureLoad(image_atlas, vec2<i32>(uv_quad.zw), 0)); |
| let fg_rgba = mix(mix(a, b, uv_frac.y), mix(c, d, uv_frac.y), uv_frac.x); |
| let fg_i = fg_rgba * area[i]; |
| rgba[i] = rgba[i] * (1.0 - fg_i.a) + fg_i; |
| } |
| } |
| cmd_ix += 2u; |
| } |
| // CMD_BEGIN_CLIP |
| case 10u: { |
| if clip_depth < BLEND_STACK_SPLIT { |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| blend_stack[clip_depth][i] = pack4x8unorm(rgba[i]); |
| rgba[i] = vec4(0.0); |
| } |
| } else { |
| // TODO: spill to memory |
| } |
| clip_depth += 1u; |
| cmd_ix += 1u; |
| } |
| // CMD_END_CLIP |
| case 11u: { |
| let end_clip = read_end_clip(cmd_ix); |
| clip_depth -= 1u; |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| var bg_rgba: u32; |
| if clip_depth < BLEND_STACK_SPLIT { |
| bg_rgba = blend_stack[clip_depth][i]; |
| } else { |
| // load from memory |
| } |
| let bg = unpack4x8unorm(bg_rgba); |
| let fg = rgba[i] * area[i] * end_clip.alpha; |
| rgba[i] = blend_mix_compose(bg, fg, end_clip.blend); |
| } |
| cmd_ix += 3u; |
| } |
| // CMD_JUMP |
| case 12u: { |
| cmd_ix = ptcl[cmd_ix + 1u]; |
| } |
| default: {} |
| } |
| } |
| let xy_uint = vec2<u32>(xy); |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| let coords = xy_uint + vec2(i, 0u); |
| if coords.x < config.target_width && coords.y < config.target_height { |
| let fg = rgba[i]; |
| // Max with a small epsilon to avoid NaNs |
| let a_inv = 1.0 / max(fg.a, 1e-6); |
| let rgba_sep = vec4(fg.rgb * a_inv, fg.a); |
| textureStore(output, vec2<i32>(coords), rgba_sep); |
| } |
| } |
| #else |
| let tile = tiles[tile_ix]; |
| var area: array<f32, PIXELS_PER_THREAD>; |
| fill_path(tile, xy, &area); |
| |
| let xy_uint = vec2<u32>(xy); |
| for (var i = 0u; i < PIXELS_PER_THREAD; i += 1u) { |
| let coords = xy_uint + vec2(i, 0u); |
| if coords.x < config.target_width && coords.y < config.target_height { |
| textureStore(output, vec2<i32>(coords), vec4(area[i])); |
| } |
| } |
| #endif |
| } |
| |
| fn premul_alpha(rgba: vec4<f32>) -> vec4<f32> { |
| return vec4(rgba.rgb * rgba.a, rgba.a); |
| } |
