1 /*
2 * Copyright 2017 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #ifndef SkDrawShadowInfo_DEFINED
9 #define SkDrawShadowInfo_DEFINED
10
11 #include "include/core/SkColor.h"
12 #include "include/core/SkPoint.h"
13 #include "include/core/SkPoint3.h"
14 #include "include/private/base/SkTPin.h"
15
16 class SkMatrix;
17 class SkPath;
18 struct SkRect;
19
20 struct SkDrawShadowRec {
21 SkPoint3 fZPlaneParams;
22 SkPoint3 fLightPos;
23 SkScalar fLightRadius;
24 SkColor fAmbientColor;
25 SkColor fSpotColor;
26 uint32_t fFlags;
27 };
28
29 namespace SkDrawShadowMetrics {
30
31 static constexpr auto kAmbientHeightFactor = 1.0f / 128.0f;
32 static constexpr auto kAmbientGeomFactor = 64.0f;
33 // Assuming that we have a light height of 600 for the spot shadow,
34 // the spot values will reach their maximum at a height of approximately 292.3077.
35 // We'll round up to 300 to keep it simple.
36 static constexpr auto kMaxAmbientRadius = 300*kAmbientHeightFactor*kAmbientGeomFactor;
37
divide_and_pin(float numer,float denom,float min,float max)38 static inline float divide_and_pin(float numer, float denom, float min, float max) {
39 float result = SkTPin(sk_ieee_float_divide(numer, denom), min, max);
40 // ensure that SkTPin handled non-finites correctly
41 SkASSERT(result >= min && result <= max);
42 return result;
43 }
44
AmbientBlurRadius(SkScalar height)45 inline SkScalar AmbientBlurRadius(SkScalar height) {
46 return std::min(height*kAmbientHeightFactor*kAmbientGeomFactor, kMaxAmbientRadius);
47 }
48
AmbientRecipAlpha(SkScalar height)49 inline SkScalar AmbientRecipAlpha(SkScalar height) {
50 return 1.0f + std::max(height*kAmbientHeightFactor, 0.0f);
51 }
52
SpotBlurRadius(SkScalar occluderZ,SkScalar lightZ,SkScalar lightRadius)53 inline SkScalar SpotBlurRadius(SkScalar occluderZ, SkScalar lightZ, SkScalar lightRadius) {
54 return lightRadius*divide_and_pin(occluderZ, lightZ - occluderZ, 0.0f, 0.95f);
55 }
56
GetSpotParams(SkScalar occluderZ,SkScalar lightX,SkScalar lightY,SkScalar lightZ,SkScalar lightRadius,SkScalar * blurRadius,SkScalar * scale,SkVector * translate)57 inline void GetSpotParams(SkScalar occluderZ, SkScalar lightX, SkScalar lightY, SkScalar lightZ,
58 SkScalar lightRadius,
59 SkScalar* blurRadius, SkScalar* scale, SkVector* translate) {
60 SkScalar zRatio = divide_and_pin(occluderZ, lightZ - occluderZ, 0.0f, 0.95f);
61 *blurRadius = lightRadius*zRatio;
62 *scale = divide_and_pin(lightZ, lightZ - occluderZ, 1.0f, 1.95f);
63 *translate = SkVector::Make(-zRatio * lightX, -zRatio * lightY);
64 }
65
GetDirectionalParams(SkScalar occluderZ,SkScalar lightX,SkScalar lightY,SkScalar lightZ,SkScalar lightRadius,SkScalar * blurRadius,SkScalar * scale,SkVector * translate)66 inline void GetDirectionalParams(SkScalar occluderZ, SkScalar lightX, SkScalar lightY,
67 SkScalar lightZ, SkScalar lightRadius,
68 SkScalar* blurRadius, SkScalar* scale, SkVector* translate) {
69 *blurRadius = lightRadius*occluderZ;
70 *scale = 1;
71 // Max z-ratio is "max expected elevation"/"min allowable z"
72 constexpr SkScalar kMaxZRatio = 64/SK_ScalarNearlyZero;
73 SkScalar zRatio = divide_and_pin(occluderZ, lightZ, 0.0f, kMaxZRatio);
74 *translate = SkVector::Make(-zRatio * lightX, -zRatio * lightY);
75 }
76
77 // Create the transformation to apply to a path to get its base shadow outline, given the light
78 // parameters and the path's 3D transformation (given by ctm and zPlaneParams).
79 // Also computes the blur radius to apply the transformed outline.
80 bool GetSpotShadowTransform(const SkPoint3& lightPos, SkScalar lightRadius,
81 const SkMatrix& ctm, const SkPoint3& zPlaneParams,
82 const SkRect& pathBounds, bool directional,
83 SkMatrix* shadowTransform, SkScalar* radius);
84
85 // get bounds prior to the ctm being applied
86 void GetLocalBounds(const SkPath&, const SkDrawShadowRec&, const SkMatrix& ctm, SkRect* bounds);
87
88 } // namespace SkDrawShadowMetrics
89
90 #endif
91