1 /* 2 * Copyright 2021 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 skgpu_tessellate_CullTest_DEFINED 9 #define skgpu_tessellate_CullTest_DEFINED 10 11 #include "include/core/SkMatrix.h" 12 #include "include/core/SkPoint.h" 13 #include "include/core/SkRect.h" 14 #include "include/private/base/SkAssert.h" 15 #include "src/base/SkVx.h" 16 17 namespace skgpu::tess { 18 19 // This class determines whether the given local-space points will be contained in the cull bounds 20 // post transform. For the versions that take >1 point, it returns whether any region of their 21 // device-space bounding box will be in the cull bounds. 22 // 23 // NOTE: Our view matrix is not a normal matrix. M*p maps to the float4 [x, y, -x, -y] in device 24 // space. We do this to aid in quick bounds calculations. The matrix also does not have a 25 // translation element. Instead we unapply the translation to the cull bounds ahead of time. 26 class CullTest { 27 public: 28 CullTest() = default; 29 CullTest(const SkRect & devCullBounds,const SkMatrix & m)30 CullTest(const SkRect& devCullBounds, const SkMatrix& m) { 31 this->set(devCullBounds, m); 32 } 33 set(const SkRect & devCullBounds,const SkMatrix & m)34 void set(const SkRect& devCullBounds, const SkMatrix& m) { 35 SkASSERT(!m.hasPerspective()); 36 // [fMatX, fMatY] maps path coordinates to the float4 [x, y, -x, -y] in device space. 37 fMatX = {m.getScaleX(), m.getSkewY(), -m.getScaleX(), -m.getSkewY()}; 38 fMatY = {m.getSkewX(), m.getScaleY(), -m.getSkewX(), -m.getScaleY()}; 39 // Store the cull bounds as [l, t, -r, -b] for faster math. 40 // Also subtract the matrix translate from the cull bounds ahead of time, rather than adding 41 // it to every point every time we test. 42 fCullBounds = {devCullBounds.fLeft - m.getTranslateX(), 43 devCullBounds.fTop - m.getTranslateY(), 44 m.getTranslateX() - devCullBounds.fRight, 45 m.getTranslateY() - devCullBounds.fBottom}; 46 } 47 48 // Returns whether M*p will be in the viewport. isVisible(SkPoint p)49 bool isVisible(SkPoint p) const { 50 // devPt = [x, y, -x, -y] in device space. 51 auto devPt = fMatX*p.fX + fMatY*p.fY; 52 // i.e., l < x && t < y && r > x && b > y. 53 return all(fCullBounds < devPt); 54 } 55 56 // Returns whether any region of the bounding box of M * p0..2 will be in the viewport. areVisible3(const SkPoint p[3])57 bool areVisible3(const SkPoint p[3]) const { 58 // Transform p0..2 to device space. 59 auto val0 = fMatY * p[0].fY; 60 auto val1 = fMatY * p[1].fY; 61 auto val2 = fMatY * p[2].fY; 62 val0 = fMatX*p[0].fX + val0; 63 val1 = fMatX*p[1].fX + val1; 64 val2 = fMatX*p[2].fX + val2; 65 // At this point: valN = {xN, yN, -xN, -yN} in device space. 66 67 // Find the device-space bounding box of p0..2. 68 val0 = max(val0, val1); 69 val0 = max(val0, val2); 70 // At this point: val0 = [r, b, -l, -t] of the device-space bounding box of p0..2. 71 72 // Does fCullBounds intersect the device-space bounding box of p0..2? 73 // i.e., l0 < r1 && t0 < b1 && r0 > l1 && b0 > t1. 74 return all(fCullBounds < val0); 75 } 76 77 // Returns whether any region of the bounding box of M * p0..3 will be in the viewport. areVisible4(const SkPoint p[4])78 bool areVisible4(const SkPoint p[4]) const { 79 // Transform p0..3 to device space. 80 auto val0 = fMatY * p[0].fY; 81 auto val1 = fMatY * p[1].fY; 82 auto val2 = fMatY * p[2].fY; 83 auto val3 = fMatY * p[3].fY; 84 val0 = fMatX*p[0].fX + val0; 85 val1 = fMatX*p[1].fX + val1; 86 val2 = fMatX*p[2].fX + val2; 87 val3 = fMatX*p[3].fX + val3; 88 // At this point: valN = {xN, yN, -xN, -yN} in device space. 89 90 // Find the device-space bounding box of p0..3. 91 val0 = max(val0, val1); 92 val2 = max(val2, val3); 93 val0 = max(val0, val2); 94 // At this point: val0 = [r, b, -l, -t] of the device-space bounding box of p0..3. 95 96 // Does fCullBounds intersect the device-space bounding box of p0..3? 97 // i.e., l0 < r1 && t0 < b1 && r0 > l1 && b0 > t1. 98 return all(fCullBounds < val0); 99 } 100 101 private: 102 // [fMatX, fMatY] maps path coordinates to the float4 [x, y, -x, -y] in device space. 103 skvx::float4 fMatX; 104 skvx::float4 fMatY; 105 skvx::float4 fCullBounds; // [l, t, -r, -b] 106 }; 107 108 } // namespace skgpu::tess 109 110 #endif // skgpu_tessellate_CullTest_DEFINED 111