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