| /* |
| * Copyright 2021 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #ifndef skgpu_tessellate_CullTest_DEFINED |
| #define skgpu_tessellate_CullTest_DEFINED |
| |
| #include "include/core/SkMatrix.h" |
| #include "include/core/SkPoint.h" |
| #include "include/core/SkRect.h" |
| #include "include/private/base/SkAssert.h" |
| #include "src/base/SkVx.h" |
| |
| namespace skgpu::tess { |
| |
| // This class determines whether the given local-space points will be contained in the cull bounds |
| // post transform. For the versions that take >1 point, it returns whether any region of their |
| // device-space bounding box will be in the cull bounds. |
| // |
| // NOTE: Our view matrix is not a normal matrix. M*p maps to the float4 [x, y, -x, -y] in device |
| // space. We do this to aid in quick bounds calculations. The matrix also does not have a |
| // translation element. Instead we unapply the translation to the cull bounds ahead of time. |
| class CullTest { |
| public: |
| CullTest() = default; |
| |
| CullTest(const SkRect& devCullBounds, const SkMatrix& m) { |
| this->set(devCullBounds, m); |
| } |
| |
| void set(const SkRect& devCullBounds, const SkMatrix& m) { |
| SkASSERT(!m.hasPerspective()); |
| // [fMatX, fMatY] maps path coordinates to the float4 [x, y, -x, -y] in device space. |
| fMatX = {m.getScaleX(), m.getSkewY(), -m.getScaleX(), -m.getSkewY()}; |
| fMatY = {m.getSkewX(), m.getScaleY(), -m.getSkewX(), -m.getScaleY()}; |
| // Store the cull bounds as [l, t, -r, -b] for faster math. |
| // Also subtract the matrix translate from the cull bounds ahead of time, rather than adding |
| // it to every point every time we test. |
| fCullBounds = {devCullBounds.fLeft - m.getTranslateX(), |
| devCullBounds.fTop - m.getTranslateY(), |
| m.getTranslateX() - devCullBounds.fRight, |
| m.getTranslateY() - devCullBounds.fBottom}; |
| } |
| |
| // Returns whether M*p will be in the viewport. |
| bool isVisible(SkPoint p) const { |
| // devPt = [x, y, -x, -y] in device space. |
| auto devPt = fMatX*p.fX + fMatY*p.fY; |
| // i.e., l < x && t < y && r > x && b > y. |
| return all(fCullBounds < devPt); |
| } |
| |
| // Returns whether any region of the bounding box of M * p0..2 will be in the viewport. |
| bool areVisible3(const SkPoint p[3]) const { |
| // Transform p0..2 to device space. |
| auto val0 = fMatY * p[0].fY; |
| auto val1 = fMatY * p[1].fY; |
| auto val2 = fMatY * p[2].fY; |
| val0 = fMatX*p[0].fX + val0; |
| val1 = fMatX*p[1].fX + val1; |
| val2 = fMatX*p[2].fX + val2; |
| // At this point: valN = {xN, yN, -xN, -yN} in device space. |
| |
| // Find the device-space bounding box of p0..2. |
| val0 = max(val0, val1); |
| val0 = max(val0, val2); |
| // At this point: val0 = [r, b, -l, -t] of the device-space bounding box of p0..2. |
| |
| // Does fCullBounds intersect the device-space bounding box of p0..2? |
| // i.e., l0 < r1 && t0 < b1 && r0 > l1 && b0 > t1. |
| return all(fCullBounds < val0); |
| } |
| |
| // Returns whether any region of the bounding box of M * p0..3 will be in the viewport. |
| bool areVisible4(const SkPoint p[4]) const { |
| // Transform p0..3 to device space. |
| auto val0 = fMatY * p[0].fY; |
| auto val1 = fMatY * p[1].fY; |
| auto val2 = fMatY * p[2].fY; |
| auto val3 = fMatY * p[3].fY; |
| val0 = fMatX*p[0].fX + val0; |
| val1 = fMatX*p[1].fX + val1; |
| val2 = fMatX*p[2].fX + val2; |
| val3 = fMatX*p[3].fX + val3; |
| // At this point: valN = {xN, yN, -xN, -yN} in device space. |
| |
| // Find the device-space bounding box of p0..3. |
| val0 = max(val0, val1); |
| val2 = max(val2, val3); |
| val0 = max(val0, val2); |
| // At this point: val0 = [r, b, -l, -t] of the device-space bounding box of p0..3. |
| |
| // Does fCullBounds intersect the device-space bounding box of p0..3? |
| // i.e., l0 < r1 && t0 < b1 && r0 > l1 && b0 > t1. |
| return all(fCullBounds < val0); |
| } |
| |
| private: |
| // [fMatX, fMatY] maps path coordinates to the float4 [x, y, -x, -y] in device space. |
| skvx::float4 fMatX; |
| skvx::float4 fMatY; |
| skvx::float4 fCullBounds; // [l, t, -r, -b] |
| }; |
| |
| } // namespace skgpu::tess |
| |
| #endif // skgpu_tessellate_CullTest_DEFINED |