blob: 3b5586b067077b4bcf03f37d31ac65e43ef043af [file] [log] [blame]
 /* * Copyright 2015 Google Inc. * * Use of this source code is governed by a BSD-style license that can be * found in the LICENSE file. */ #include "SkPoint3.h" // Returns the square of the Euclidian distance to (x,y,z). static inline float get_length_squared(float x, float y, float z) { return x * x + y * y + z * z; } // Calculates the square of the Euclidian distance to (x,y,z) and stores it in // *lengthSquared. Returns true if the distance is judged to be "nearly zero". // // This logic is encapsulated in a helper method to make it explicit that we // always perform this check in the same manner, to avoid inconsistencies // (see http://code.google.com/p/skia/issues/detail?id=560 ). static inline bool is_length_nearly_zero(float x, float y, float z, float *lengthSquared) { *lengthSquared = get_length_squared(x, y, z); return *lengthSquared <= (SK_ScalarNearlyZero * SK_ScalarNearlyZero); } SkScalar SkPoint3::Length(SkScalar x, SkScalar y, SkScalar z) { float magSq = get_length_squared(x, y, z); if (SkScalarIsFinite(magSq)) { return sk_float_sqrt(magSq); } else { double xx = x; double yy = y; double zz = z; return (float)sqrt(xx * xx + yy * yy + zz * zz); } } /* * We have to worry about 2 tricky conditions: * 1. underflow of magSq (compared against nearlyzero^2) * 2. overflow of magSq (compared w/ isfinite) * * If we underflow, we return false. If we overflow, we compute again using * doubles, which is much slower (3x in a desktop test) but will not overflow. */ bool SkPoint3::normalize() { float magSq; if (is_length_nearly_zero(fX, fY, fZ, &magSq)) { this->set(0, 0, 0); return false; } float scale; if (SkScalarIsFinite(magSq)) { scale = 1.0f / sk_float_sqrt(magSq); } else { // our magSq step overflowed to infinity, so use doubles instead. // much slower, but needed when x, y or z is very large, otherwise we // divide by inf. and return (0,0,0) vector. double xx = fX; double yy = fY; double zz = fZ; #ifdef SK_CPU_FLUSH_TO_ZERO // The iOS ARM processor discards small denormalized numbers to go faster. // Casting this to a float would cause the scale to go to zero. Keeping it // as a double for the multiply keeps the scale non-zero. double dscale = 1.0f / sqrt(xx * xx + yy * yy + zz * zz); fX = x * dscale; fY = y * dscale; fZ = z * dscale; return true; #else scale = (float)(1.0f / sqrt(xx * xx + yy * yy + zz * zz)); #endif } fX *= scale; fY *= scale; fZ *= scale; return true; }