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/SkTPin.h"
15
16 class SkMatrix;
17 class SkPath;
18 struct SkRect;
19
20 struct SK_API SkDrawShadowRec {
21 SkPoint3 fZPlaneParams;
22 SkPoint3 fLightPos;
23 SkScalar fLightRadius;
24 SkColor fAmbientColor;
25 SkColor fSpotColor;
26 uint32_t fFlags;
27
28 /** Writes text representation of SkDrawShadowRec to string.
29
30 @param desc the string storing a description of parameters.
31 @param depth the number of tabs preceding each line.
32 */
33 void dump(std::string& desc, int depth) const;
34 };
35
36 namespace SkDrawShadowMetrics {
37
38 static constexpr auto kAmbientHeightFactor = 1.0f / 128.0f;
39 static constexpr auto kAmbientGeomFactor = 64.0f;
40 // Assuming that we have a light height of 600 for the spot shadow,
41 // the spot values will reach their maximum at a height of approximately 292.3077.
42 // We'll round up to 300 to keep it simple.
43 static constexpr auto kMaxAmbientRadius = 300*kAmbientHeightFactor*kAmbientGeomFactor;
44
divide_and_pin(float numer,float denom,float min,float max)45 static inline float divide_and_pin(float numer, float denom, float min, float max) {
46 float result = SkTPin(sk_ieee_float_divide(numer, denom), min, max);
47 // ensure that SkTPin handled non-finites correctly
48 SkASSERT(result >= min && result <= max);
49 return result;
50 }
51
AmbientBlurRadius(SkScalar height)52 inline SkScalar AmbientBlurRadius(SkScalar height) {
53 return std::min(height*kAmbientHeightFactor*kAmbientGeomFactor, kMaxAmbientRadius);
54 }
55
AmbientRecipAlpha(SkScalar height)56 inline SkScalar AmbientRecipAlpha(SkScalar height) {
57 return 1.0f + std::max(height*kAmbientHeightFactor, 0.0f);
58 }
59
SpotBlurRadius(SkScalar occluderZ,SkScalar lightZ,SkScalar lightRadius)60 inline SkScalar SpotBlurRadius(SkScalar occluderZ, SkScalar lightZ, SkScalar lightRadius) {
61 return lightRadius*divide_and_pin(occluderZ, lightZ - occluderZ, 0.0f, 0.95f);
62 }
63
GetSpotParams(SkScalar occluderZ,SkScalar lightX,SkScalar lightY,SkScalar lightZ,SkScalar lightRadius,SkScalar * blurRadius,SkScalar * scale,SkVector * translate)64 inline void GetSpotParams(SkScalar occluderZ, SkScalar lightX, SkScalar lightY, SkScalar lightZ,
65 SkScalar lightRadius,
66 SkScalar* blurRadius, SkScalar* scale, SkVector* translate) {
67 SkScalar zRatio = divide_and_pin(occluderZ, lightZ - occluderZ, 0.0f, 0.95f);
68 *blurRadius = lightRadius*zRatio;
69 *scale = divide_and_pin(lightZ, lightZ - occluderZ, 1.0f, 1.95f);
70 *translate = SkVector::Make(-zRatio * lightX, -zRatio * lightY);
71 }
72
GetDirectionalParams(SkScalar occluderZ,SkScalar lightX,SkScalar lightY,SkScalar lightZ,SkScalar lightRadius,SkScalar * blurRadius,SkScalar * scale,SkVector * translate)73 inline void GetDirectionalParams(SkScalar occluderZ, SkScalar lightX, SkScalar lightY,
74 SkScalar lightZ, SkScalar lightRadius,
75 SkScalar* blurRadius, SkScalar* scale, SkVector* translate) {
76 *blurRadius = lightRadius*occluderZ;
77 *scale = 1;
78 // Max z-ratio is "max expected elevation"/"min allowable z"
79 constexpr SkScalar kMaxZRatio = 64/SK_ScalarNearlyZero;
80 SkScalar zRatio = divide_and_pin(occluderZ, lightZ, 0.0f, kMaxZRatio);
81 *translate = SkVector::Make(-zRatio * lightX, -zRatio * lightY);
82 }
83
84 // Create the transformation to apply to a path to get its base shadow outline, given the light
85 // parameters and the path's 3D transformation (given by ctm and zPlaneParams).
86 // Also computes the blur radius to apply the transformed outline.
87 bool GetSpotShadowTransform(const SkPoint3& lightPos, SkScalar lightRadius,
88 const SkMatrix& ctm, const SkPoint3& zPlaneParams,
89 const SkRect& pathBounds, bool directional,
90 SkMatrix* shadowTransform, SkScalar* radius);
91
92 // get bounds prior to the ctm being applied
93 void GetLocalBounds(const SkPath&, const SkDrawShadowRec&, const SkMatrix& ctm, SkRect* bounds);
94
95 } // namespace SkDrawShadowMetrics
96
97 #endif
98