1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
|
/*
* 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;
}
|
