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fix certain slopes not having gaps

This commit is contained in:
Jaklyy 2023-07-27 02:23:36 -04:00
parent 7caddf9615
commit 9dc9e1c61a
1 changed files with 33 additions and 11 deletions
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44
src/GPU3D_Soft.h
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@ -280,7 +280,6 @@ private:
// slope increment has a 18-bit fractional part
// note: for some reason, x/y isn't calculated directly,
// instead, 1/y is calculated and then multiplied by x
// TODO: this is still not perfect (see for example x=169 y=33)
if (ylen == 0)
Increment = 0;
else if (ylen == xlen && xlen != 1)
@ -313,21 +312,41 @@ private:
dx += (y - y0) * Increment;
if (XMajor)
{
// used for calculating AA coverage
xcov_incr = (ylen << 10) / xlen;
if (side ^ Negative)
{
dxold = dx;
// I dont think the first span can have a gap but i think its technically correct to do this calc anyway?
// could probably be removed as a minor optimization
dx &= ~0x1FF;
}
}
s32 x = XVal();
int interpoffset = (Increment >= 0x40000) && (side ^ Negative);
Interp.Setup(y0-interpoffset, y1-interpoffset, w0, w1);
Interp.SetX(y);
// used for calculating AA coverage
if (XMajor) xcov_incr = (ylen << 10) / xlen;
return x;
}
constexpr s32 Step()
{
dx += Increment;
{
if (XMajor && (side ^ Negative)) // tl, br (right side start) & tr, bl (left side start)
{
// round dx; required to create gaps in lines like on hw
// increment using dxold to make the line not completely borked after rendering a gap
dx = (dxold & ~0x1FF) + Increment;
dxold += Increment;
}
else
dx += Increment;
y++;
s32 x = XVal();
@ -353,15 +372,18 @@ private:
// only needed for aa calcs, as actual line spans are broken
if constexpr (!swapped || side)
{
if (side ^ Negative)
*length = (dx >> 18) - ((dx-Increment) >> 18);
else
*length = ((dx+Increment) >> 18) - (dx >> 18);
if (side ^ Negative) // tr, bl (left side end) & tl br (right side end)
// dxold used here to avoid rounding the endpoint
*length = (dx >> 18) - (dxold - Increment >> 18);
else // tl, br (left side end) & tr, bl (right side end)
// dx rounded down to create gaps in lines like on hw
*length = ((dx & ~0x1FF) + Increment >> 18) - (dx >> 18);
}
// for X-major edges, we return the coverage
// for the first pixel, and the increment for
// further pixels on the same scanline
// TODO: check how coverage interacts with line gaps
s32 startx = dx >> 18;
if (Negative) startx = xlen - startx;
if (side) startx = startx - *length + 1;
@ -421,7 +443,7 @@ private:
private:
s32 x0, xmin, xmax;
s32 xlen, ylen;
s32 dx;
s32 dx, dxold;
s32 y;
s32 xcov_incr;