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some work on extreme/degenerate shit in GPU

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* clip against Z then Y then X. apparently, fixes #310. I had also observed hints that the hardware does it this way.
* truncate W to 24 bits before viewport transform.
* mark any polygons that have a W=0 at that point as degenerate. do not render.
This commit is contained in:
StapleButter
2018-12-20 01:31:31 +01:00
parent 1a8b18af2c
commit f6e6fa05ea
3 changed files with 32 additions and 9 deletions
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35
src/GPU3D.cpp
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@ -537,6 +537,19 @@ void DoSavestate(Savestate* file)
file->Var32((u32*)&poly->XBottom);
file->Var32(&poly->SortKey);
if (!file->Saving)
{
poly->Degenerate = false;
for (int j = 0; j < poly->NumVertices; j++)
{
if (poly->Vertices[j]->Position[3] == 0)
poly->Degenerate = true;
}
if (poly->YBottom > 192) poly->Degenerate = true;
}
}
// probably not worth storing the vblank-latched Renderxxxxxx variables
@ -945,16 +958,14 @@ int ClipPolygon(Vertex* vertices, int nverts, int clipstart)
// some vertices that should get Y=-0x1000 get Y=0x1000 for some reason on hardware. it doesn't make sense.
// clipping seems to process the Y plane before the X plane.
// also, polygons with any negative W are completely rejected. (TODO)
// X clipping
nverts = ClipAgainstPlane<0, attribs>(vertices, nverts, clipstart);
// Z clipping
nverts = ClipAgainstPlane<2, attribs>(vertices, nverts, clipstart);
// Y clipping
nverts = ClipAgainstPlane<1, attribs>(vertices, nverts, clipstart);
// Z clipping
nverts = ClipAgainstPlane<2, attribs>(vertices, nverts, clipstart);
// X clipping
nverts = ClipAgainstPlane<0, attribs>(vertices, nverts, clipstart);
return nverts;
}
@ -1105,6 +1116,8 @@ void SubmitPolygon()
poly->TexParam = TexParam;
poly->TexPalette = TexPalette;
poly->Degenerate = false;
poly->FacingView = facingview;
u32 texfmt = (TexParam >> 26) & 0x7;
@ -1147,6 +1160,10 @@ void SubmitPolygon()
NumVertices++;
poly->NumVertices++;
// W is truncated to 24 bits at this point
// if this W is zero, the polygon isn't rendered
vtx->Position[3] &= 0x00FFFFFF;
// viewport transform
s32 posX, posY;
s32 w = vtx->Position[3];
@ -1154,6 +1171,7 @@ void SubmitPolygon()
{
posX = 0;
posY = 0;
poly->Degenerate = true;
}
else
{
@ -1208,6 +1226,8 @@ void SubmitPolygon()
poly->YTop = ytop; poly->YBottom = ybot;
poly->XTop = xtop; poly->XBottom = xbot;
if (ybot > 192) poly->Degenerate = true;
poly->SortKey = (ybot << 8) | ytop;
if (poly->Translucent) poly->SortKey |= 0x10000;
@ -1267,6 +1287,9 @@ void SubmitVertex()
vertextrans->Position[2] = (vertex[0]*ClipMatrix[2] + vertex[1]*ClipMatrix[6] + vertex[2]*ClipMatrix[10] + vertex[3]*ClipMatrix[14]) >> 12;
vertextrans->Position[3] = (vertex[0]*ClipMatrix[3] + vertex[1]*ClipMatrix[7] + vertex[2]*ClipMatrix[11] + vertex[3]*ClipMatrix[15]) >> 12;
//vertextrans->Position[3] &= 0x00FFFFFF;
//if (vertextrans->Position[3] < 0) printf("NEGATIVE W: %08X\n", vertextrans->Position[3]);
// this probably shouldn't be.
// the way color is handled during clipping needs investigation. TODO
vertextrans->Color[0] = (VertexColor[0] << 12) + 0xFFF;