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- /*
- * 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 "include/core/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;
- }
- // sqrtf does not provide enough precision; since sqrt takes a double,
- // there's no additional penalty to storing invScale in a double
- double invScale;
- if (sk_float_isfinite(magSq)) {
- invScale = 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;
- invScale = xx * xx + yy * yy + zz * zz;
- }
- // using a float instead of a double for scale loses too much precision
- double scale = 1 / sqrt(invScale);
- fX *= scale;
- fY *= scale;
- fZ *= scale;
- if (!sk_float_isfinite(fX) || !sk_float_isfinite(fY) || !sk_float_isfinite(fZ)) {
- this->set(0, 0, 0);
- return false;
- }
- return true;
- }
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