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Fix Incorrect Polygon Swapping Behavior and Implement Correct Rules for Shifting Right Edges Left (#1816)

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* fix polygons being swapped incorrectly

"borrowed" this from noods
needs verification that the >= and <= signs aren't actually supposed to be > and <

* proper rules for moving vertical right slopes left

* nvm most of that was actually pointless

that's on me for not checking
This commit is contained in:
Jaklyy
2023-08-27 07:29:12 -04:00
committed by GitHub
parent dc8efb62b8
commit d69745b3a8
3 changed files with 14 additions and 13 deletions
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10
src/GPU3D_Soft.cpp
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@ -742,6 +742,11 @@ void SoftRenderer::RenderShadowMaskScanline(RendererPolygon* rp, s32 y)
s32 zl = rp->SlopeL.Interp.InterpolateZ(polygon->FinalZ[rp->CurVL], polygon->FinalZ[rp->NextVL], polygon->WBuffer);
s32 zr = rp->SlopeR.Interp.InterpolateZ(polygon->FinalZ[rp->CurVR], polygon->FinalZ[rp->NextVR], polygon->WBuffer);
// right vertical edges are pushed 1px to the left as long as either:
// the left edge slope is not 0, or the span is not 0 pixels wide, and it is not at the leftmost pixel of the screen
if (rp->SlopeR.Increment==0 && (rp->SlopeL.Increment!=0 || xstart != xend) && (xend != 0))
xend--;
// if the left and right edges are swapped, render backwards.
if (xstart > xend)
{
@ -955,6 +960,11 @@ void SoftRenderer::RenderPolygonScanline(RendererPolygon* rp, s32 y)
s32 zl = rp->SlopeL.Interp.InterpolateZ(polygon->FinalZ[rp->CurVL], polygon->FinalZ[rp->NextVL], polygon->WBuffer);
s32 zr = rp->SlopeR.Interp.InterpolateZ(polygon->FinalZ[rp->CurVR], polygon->FinalZ[rp->NextVR], polygon->WBuffer);
// right vertical edges are pushed 1px to the left as long as either:
// the left edge slope is not 0, or the span is not 0 pixels wide, and it is not at the leftmost pixel of the screen
if (rp->SlopeR.Increment==0 && (rp->SlopeL.Increment!=0 || xstart != xend) && (xend != 0))
xend--;
// if the left and right edges are swapped, render backwards.
// on hardware, swapped edges seem to break edge length calculation,