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[mtl canvas] don't reorder point to make clockwise triangles. Instead, store triangle orientation in triangle struct and multiply orientation in raster test

This commit is contained in:
Martin Fouilleul 2023-03-14 15:08:39 +01:00
parent 221fcbeb6b
commit 5c1a220f1f
2 changed files with 15 additions and 20 deletions
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2
src/mtl_shader.h
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@ -52,6 +52,8 @@ typedef struct mg_triangle_data
int bias1;
int bias2;
int cw;
int shapeIndex;
} mg_triangle_data;

33
src/mtl_shader.metal
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@ -56,31 +56,20 @@ kernel void TileKernel(constant mg_vertex* vertexBuffer [[buffer(0)]],
float2 p1 = vertexBuffer[i1].pos * scaling[0];
float2 p2 = vertexBuffer[i2].pos * scaling[0];
//NOTE(martin): compute triangle bounding box
int shapeIndex = vertexBuffer[i0].shapeIndex;
//NOTE(martin): compute triangle bounding box and clip it
float2 boxMin = min(min(p0, p1), p2);
float2 boxMax = max(max(p0, p1), p2);
//NOTE(martin): clip bounding box against clip rect
int shapeIndex = vertexBuffer[i0].shapeIndex;
vector_float4 clip = scaling[0]*shapeBuffer[shapeIndex].clip;
//NOTE(martin): intersect with current clip
boxMin = max(boxMin, clip.xy);
boxMax = min(boxMax, clip.zw);
//NOTE(martin): reorder triangle counter-clockwise and compute bias for each edge
float cw = (p1 - p0).x*(p2 - p0).y - (p1 - p0).y*(p2 - p0).x;
if(cw < 0)
{
uint tmpIndex = i1;
i1 = i2;
i2 = tmpIndex;
//NOTE(martin): compute triangle orientation and bias for each edge
int cw = ((p1 - p0).x*(p2 - p0).y - (p1 - p0).y*(p2 - p0).x) > 0 ? 1 : -1;
float2 tmpPoint = p1;
p1 = p2;
p2 = tmpPoint;
}
int bias0 = is_top_left(p1, p2) ? 0 : -1;
int bias1 = is_top_left(p2, p0) ? 0 : -1;
int bias2 = is_top_left(p0, p1) ? 0 : -1;
@ -112,9 +101,11 @@ kernel void TileKernel(constant mg_vertex* vertexBuffer [[buffer(0)]],
triangleArray[gid].bias1 = bias1;
triangleArray[gid].bias2 = bias2;
triangleArray[gid].cw = cw;
int4 box = int4(floor(fbox))/RENDERER_TILE_SIZE;
//NOTE(martin): it's importat to do the computation with signed int, so that we can have negative xMax/yMax
//NOTE(martin): it's important to do the computation with signed int, so that we can have negative xMax/yMax
// otherwise all triangles on the left or below the x/y axis are attributed to tiles on row/column 0.
int xMin = max(0, box.x);
int yMin = max(0, box.y);
@ -274,6 +265,8 @@ kernel void RenderKernel(const device uint* tileCounters [[buffer(0)]],
int2 p1 = triangle->p1;
int2 p2 = triangle->p2;
int cw = triangle->cw;
int bias0 = triangle->bias0;
int bias1 = triangle->bias1;
int bias2 = triangle->bias2;
@ -302,9 +295,9 @@ kernel void RenderKernel(const device uint* tileCounters [[buffer(0)]],
continue;
}
int w0 = orient2d(p1, p2, samplePoint);
int w1 = orient2d(p2, p0, samplePoint);
int w2 = orient2d(p0, p1, samplePoint);
int w0 = cw*orient2d(p1, p2, samplePoint);
int w1 = cw*orient2d(p2, p0, samplePoint);
int w2 = cw*orient2d(p0, p1, samplePoint);
if((w0+bias0) >= 0 && (w1+bias1) >= 0 && (w2+bias2) >= 0)
{