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 "SkColor.h"
12 #include "SkPoint.h"
13 #include "SkPoint3.h"
14
15 class SkMatrix;
16 class SkPath;
17 struct SkRect;
18
19 struct SkDrawShadowRec {
20 SkPoint3 fZPlaneParams;
21 SkPoint3 fLightPos;
22 SkScalar fLightRadius;
23 SkColor fAmbientColor;
24 SkColor fSpotColor;
25 uint32_t fFlags;
26 };
27
28 namespace SkDrawShadowMetrics {
29
30 static constexpr auto kAmbientHeightFactor = 1.0f / 128.0f;
31 static constexpr auto kAmbientGeomFactor = 64.0f;
32 // Assuming that we have a light height of 600 for the spot shadow,
33 // the spot values will reach their maximum at a height of approximately 292.3077.
34 // We'll round up to 300 to keep it simple.
35 static constexpr auto kMaxAmbientRadius = 300*kAmbientHeightFactor*kAmbientGeomFactor;
36
divide_and_pin(float numer,float denom,float min,float max)37 static inline float divide_and_pin(float numer, float denom, float min, float max) {
38 float result = SkTPin(sk_ieee_float_divide(numer, denom), min, max);
39 // ensure that SkTPin handled non-finites correctly
40 SkASSERT(result >= min && result <= max);
41 return result;
42 }
43
AmbientBlurRadius(SkScalar height)44 inline SkScalar AmbientBlurRadius(SkScalar height) {
45 return SkTMin(height*kAmbientHeightFactor*kAmbientGeomFactor, kMaxAmbientRadius);
46 }
47
AmbientRecipAlpha(SkScalar height)48 inline SkScalar AmbientRecipAlpha(SkScalar height) {
49 return 1.0f + SkTMax(height*kAmbientHeightFactor, 0.0f);
50 }
51
SpotBlurRadius(SkScalar occluderZ,SkScalar lightZ,SkScalar lightRadius)52 inline SkScalar SpotBlurRadius(SkScalar occluderZ, SkScalar lightZ, SkScalar lightRadius) {
53 return lightRadius*divide_and_pin(occluderZ, lightZ - occluderZ, 0.0f, 0.95f);
54 }
55
GetSpotParams(SkScalar occluderZ,SkScalar lightX,SkScalar lightY,SkScalar lightZ,SkScalar lightRadius,SkScalar * blurRadius,SkScalar * scale,SkVector * translate)56 inline void GetSpotParams(SkScalar occluderZ, SkScalar lightX, SkScalar lightY, SkScalar lightZ,
57 SkScalar lightRadius,
58 SkScalar* blurRadius, SkScalar* scale, SkVector* translate) {
59 SkScalar zRatio = divide_and_pin(occluderZ, lightZ - occluderZ, 0.0f, 0.95f);
60 *blurRadius = lightRadius*zRatio;
61 *scale = divide_and_pin(lightZ, lightZ - occluderZ, 1.0f, 1.95f);
62 *translate = SkVector::Make(-zRatio * lightX, -zRatio * lightY);
63 }
64
65 // Create the transformation to apply to a path to get its base shadow outline, given the light
66 // parameters and the path's 3D transformation (given by ctm and zPlaneParams).
67 // Also computes the blur radius to apply the transformed outline.
68 bool GetSpotShadowTransform(const SkPoint3& lightPos, SkScalar lightRadius,
69 const SkMatrix& ctm, const SkPoint3& zPlaneParams,
70 const SkRect& pathBounds, SkMatrix* shadowTransform, SkScalar* radius);
71
72 // get bounds prior to the ctm being applied
73 void GetLocalBounds(const SkPath&, const SkDrawShadowRec&, const SkMatrix& ctm, SkRect* bounds);
74
75 }
76
77 #endif
78