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* Copyright 2017 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef SkDrawShadowInfo_DEFINED
#define SkDrawShadowInfo_DEFINED
#include "include/core/SkColor.h"
#include "include/core/SkPoint.h"
#include "include/core/SkPoint3.h"
class SkMatrix;
class SkPath;
struct SkRect;
struct SkDrawShadowRec {
SkPoint3 fZPlaneParams;
SkPoint3 fLightPos;
SkScalar fLightRadius;
SkColor fAmbientColor;
SkColor fSpotColor;
uint32_t fFlags;
namespace SkDrawShadowMetrics {
static constexpr auto kAmbientHeightFactor = 1.0f / 128.0f;
static constexpr auto kAmbientGeomFactor = 64.0f;
// Assuming that we have a light height of 600 for the spot shadow,
// the spot values will reach their maximum at a height of approximately 292.3077.
// We'll round up to 300 to keep it simple.
static constexpr auto kMaxAmbientRadius = 300*kAmbientHeightFactor*kAmbientGeomFactor;
static inline float divide_and_pin(float numer, float denom, float min, float max) {
float result = SkTPin(sk_ieee_float_divide(numer, denom), min, max);
// ensure that SkTPin handled non-finites correctly
SkASSERT(result >= min && result <= max);
return result;
inline SkScalar AmbientBlurRadius(SkScalar height) {
return std::min(height*kAmbientHeightFactor*kAmbientGeomFactor, kMaxAmbientRadius);
inline SkScalar AmbientRecipAlpha(SkScalar height) {
return 1.0f + std::max(height*kAmbientHeightFactor, 0.0f);
inline SkScalar SpotBlurRadius(SkScalar occluderZ, SkScalar lightZ, SkScalar lightRadius) {
return lightRadius*divide_and_pin(occluderZ, lightZ - occluderZ, 0.0f, 0.95f);
inline void GetSpotParams(SkScalar occluderZ, SkScalar lightX, SkScalar lightY, SkScalar lightZ,
SkScalar lightRadius,
SkScalar* blurRadius, SkScalar* scale, SkVector* translate) {
SkScalar zRatio = divide_and_pin(occluderZ, lightZ - occluderZ, 0.0f, 0.95f);
*blurRadius = lightRadius*zRatio;
*scale = divide_and_pin(lightZ, lightZ - occluderZ, 1.0f, 1.95f);
*translate = SkVector::Make(-zRatio * lightX, -zRatio * lightY);
// Create the transformation to apply to a path to get its base shadow outline, given the light
// parameters and the path's 3D transformation (given by ctm and zPlaneParams).
// Also computes the blur radius to apply the transformed outline.
bool GetSpotShadowTransform(const SkPoint3& lightPos, SkScalar lightRadius,
const SkMatrix& ctm, const SkPoint3& zPlaneParams,
const SkRect& pathBounds, SkMatrix* shadowTransform, SkScalar* radius);
// get bounds prior to the ctm being applied
void GetLocalBounds(const SkPath&, const SkDrawShadowRec&, const SkMatrix& ctm, SkRect* bounds);