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@ -967,50 +967,58 @@ void GPU3D::SubmitPolygon() noexcept
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VertexSlotCounter = 1;
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VertexSlotsFree = 0b11110;
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// culling
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// polygon orientation
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// TODO: work out how it works on the real thing
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// the normalization part is a wild guess
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Vertex *v0, *v1, *v2, *v3;
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Vertex *v0, *v1, *v2;
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s64 normalX, normalY, normalZ;
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s64 dot;
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bool facingview;
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v0 = &TempVertexBuffer[0];
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v1 = &TempVertexBuffer[1];
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v2 = &TempVertexBuffer[2];
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v3 = &TempVertexBuffer[3];
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normalX = ((s64)(v0->Position[1]-v1->Position[1]) * (v2->Position[3]-v1->Position[3]))
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- ((s64)(v0->Position[3]-v1->Position[3]) * (v2->Position[1]-v1->Position[1]));
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normalY = ((s64)(v0->Position[3]-v1->Position[3]) * (v2->Position[0]-v1->Position[0]))
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- ((s64)(v0->Position[0]-v1->Position[0]) * (v2->Position[3]-v1->Position[3]));
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normalZ = ((s64)(v0->Position[0]-v1->Position[0]) * (v2->Position[1]-v1->Position[1]))
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- ((s64)(v0->Position[1]-v1->Position[1]) * (v2->Position[0]-v1->Position[0]));
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while ((((normalX>>31) ^ (normalX>>63)) != 0) ||
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(((normalY>>31) ^ (normalY>>63)) != 0) ||
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(((normalZ>>31) ^ (normalZ>>63)) != 0))
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// setup vectors for v0->v2 and v1->v2, with w serving as the z axis
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s64 vector0[3] = { (s64)v0->Position[0] - v2->Position[0], (s64)v0->Position[1] - v2->Position[1], (s64)v0->Position[3] - v2->Position[3] };
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s64 vector1[3] = { (s64)v1->Position[0] - v2->Position[0], (s64)v1->Position[1] - v2->Position[1], (s64)v1->Position[3] - v2->Position[3] };
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// if either vector is entirely 0, the polygon is accepted, and the front facing flag is set for the rasterizer
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if (((vector0[0] | vector0[1] | vector0[2]) == 0) || ((vector1[0] | vector1[1] | vector1[2]) == 0))
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{
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normalX >>= 4;
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normalY >>= 4;
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normalZ >>= 4;
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facingview = true;
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}
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dot = ((s64)v1->Position[0] * normalX) + ((s64)v1->Position[1] * normalY) + ((s64)v1->Position[3] * normalZ);
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bool facingview = (dot <= 0);
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if (dot < 0)
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else
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{
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if (!(CurPolygonAttr & (1<<7)))
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// calculate cross product of the two vectors
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normalX = ((s64)vector0[1] * vector1[2]) - ((s64)vector0[2] * vector1[1]);
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normalY = ((s64)vector0[2] * vector1[0]) - ((s64)vector0[0] * vector1[2]);
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normalZ = ((s64)vector0[0] * vector1[1]) - ((s64)vector0[1] * vector1[0]);
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// normalization (currently a guess)
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while ((((normalX>>31) ^ (normalX>>63)) != 0) ||
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(((normalY>>31) ^ (normalY>>63)) != 0) ||
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(((normalZ>>31) ^ (normalZ>>63)) != 0))
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{
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LastStripPolygon = NULL;
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return;
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normalX >>= 4;
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normalY >>= 4;
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normalZ >>= 4;
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}
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}
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else if (dot > 0)
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{
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if (!(CurPolygonAttr & (1<<6)))
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// calculate dot product against the "camera vector" (we can use any of the vertices to do that)
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dot = (v1->Position[0] * normalX) + (v1->Position[1] * normalY) + (v1->Position[3] * normalZ);
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// front facing flag is set for the rasterizer to be used for:
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// unwinding vertices
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// determining whether slopes should be treated as "swapped"
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// and whether to overwrite a pixel with equal depth when using the < depth test
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facingview = (dot >= 0);
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// cull polygon faces
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if (!(((dot >= 0) && (CurPolygonAttr & (1<<7))) || // front facing
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((dot <= 0) && (CurPolygonAttr & (1<<6))))) // back facing
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{
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LastStripPolygon = NULL;
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return;
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