mirror of
https://github.com/nzp-team/fteqw.git
synced 2024-12-13 05:40:46 +00:00
324 lines
5.9 KiB
C
324 lines
5.9 KiB
C
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/*
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this file is expected to be #included as the body of a real function
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to define create a new pixel shader, define PLOT_PIXEL(outval) at the top of your function and you're good to go
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//modifiers:
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SPAN_ST - interpolates S+T across the span. access with 'sc' and 'tc'
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affine... no perspective correction.
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*/
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{
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swvert_t *vt;
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int y;
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int secondhalf;
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int xl,xld, xr,xrd;
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#ifdef SPAN_ST
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float sl,sld, sd;
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float tl,tld, td;
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#endif
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#ifdef SPAN_Z
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unsigned int zl,zld, zd;
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#endif
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unsigned int *restrict outbuf;
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unsigned int *restrict ti;
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int i;
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const swvert_t *vlt,*vlb,*vrt,*vrb;
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int spanlen;
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int numspans;
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unsigned int *vplout;
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int dx, dy;
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int recalcside;
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int interlace;
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float fdx1,fdy1,fdx2,fdy2,fz,d1,d2;
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if (!img)
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return;
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/*we basically render a diamond
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that is, the single triangle is split into two triangles, outwards towards the midpoint and inwards to the final position.
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*/
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/*reorder the verticies for height*/
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if (v1->vcoord[1] > v2->vcoord[1])
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{
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vt = v1;
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v1 = v2;
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v2 = vt;
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}
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if (v1->vcoord[1] > v3->vcoord[1])
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{
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vt = v1;
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v1 = v3;
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v3 = vt;
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}
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if (v2->vcoord[1] > v3->vcoord[1])
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{
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vt = v3;
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v3 = v2;
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v2 = vt;
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}
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{
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const swvert_t *v[3];
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v[0] = v1;
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v[1] = v2;
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v[2] = v3;
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//reject triangles with any point offscreen, for now
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for (i = 0; i < 3; i++)
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{
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if (v[i]->vcoord[0] < 0 || v[i]->vcoord[0] >= th->vpwidth)
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return;
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if (v[i]->vcoord[1] < 0 || v[i]->vcoord[1] >= th->vpheight)
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return;
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if (v[i]->vcoord[2] < 0)
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return;
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}
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for (i = 0; i < 2; i++)
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{
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if (v[i]->vcoord[1] > v[i+1]->vcoord[1])
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return;
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}
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}
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fdx1 = v2->vcoord[0] - v1->vcoord[0];
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fdy1 = v2->vcoord[1] - v1->vcoord[1];
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fdx2 = v3->vcoord[0] - v1->vcoord[0];
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fdy2 = v3->vcoord[1] - v1->vcoord[1];
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fz = fdx1*fdy2 - fdx2*fdy1;
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if (fz == 0)
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{
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//weird angle...
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return;
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}
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fz = 1.0 / fz;
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fdx1 *= fz;
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fdy1 *= fz;
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fdx2 *= fz;
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fdy2 *= fz;
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#ifdef SPAN_ST //affine
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d1 = v2->tccoord[0] - v1->tccoord[0];
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d2 = v3->tccoord[0] - v1->tccoord[0];
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sld = fdx1*d2 - fdx2*d1;
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sd = fdy2*d1 - fdy1*d2;
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d1 = v2->tccoord[1] - v1->tccoord[1];
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d2 = v3->tccoord[1] - v1->tccoord[1];
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tld = fdx1*d2 - fdx2*d1;
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td = fdy2*d1 - fdy1*d2;
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#endif
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#ifdef SPAN_Z
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d1 = (v2->vcoord[2] - v1->vcoord[2])*UINT_MAX;
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d2 = (v3->vcoord[2] - v1->vcoord[2])*UINT_MAX;
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zld = fdx1*d2 - fdx2*d1;
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zd = fdy2*d1 - fdy1*d2;
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#endif
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ti = img->data;
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y = v1->vcoord[1];
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for (secondhalf = 0; secondhalf <= 1; secondhalf++)
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{
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if (secondhalf)
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{
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if (numspans < 0)
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{
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interlace = -numspans;
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y+=interlace;
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numspans-=interlace;
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xl += xld*interlace;
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xr += xrd*interlace;
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vplout += th->vpcstride*interlace;
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#ifdef SPAN_ST
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sl += sld*interlace;
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tl += tld*interlace;
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#endif
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#ifdef SPAN_Z
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zl += zld*interlace;
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#endif
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}
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/*v2->v3*/
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if (fz <= 0)
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{
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vlt = v2;
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//vrt == v1;
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vlb = v3;
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//vrb == v3;
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recalcside = 1;
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#ifdef SPAN_ST
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sld -= sd*xld/(float)(1<<16);
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tld -= td*xld/(float)(1<<16);
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#endif
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#ifdef SPAN_Z
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zld -= zd*xld/(float)(1<<16);
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#endif
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}
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else
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{
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//vlt == v1;
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vrt = v2;
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///vlb == v3;
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vrb = v3;
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recalcside = 2;
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}
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//flip the triangle to keep it facing the screen (we swapped the verts almost randomly)
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numspans = v3->vcoord[1] - y;
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}
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else
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{
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vlt = v1;
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vrt = v1;
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/*v1->v2*/
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if (fz < 0)
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{
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vlb = v2;
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vrb = v3;
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}
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else
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{
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vlb = v3;
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vrb = v2;
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}
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recalcside = 3;
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//flip the triangle to keep it facing the screen (we swapped the verts almost randomly)
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numspans = v2->vcoord[1] - y;
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}
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if (recalcside & 1)
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{
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dx = (vlb->vcoord[0] - vlt->vcoord[0]);
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dy = (vlb->vcoord[1] - vlt->vcoord[1]);
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if (dy > 0)
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xld = (dx<<16) / dy;
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else
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xld = 0;
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xl = (int)vlt->vcoord[0]<<16;
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#ifdef SPAN_ST
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sl = vlt->tccoord[0];
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sld = sld + sd*xld/(float)(1<<16);
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tl = vlt->tccoord[1];
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tld = tld + td*xld/(float)(1<<16);
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#endif
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#ifdef SPAN_Z
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zl = vlt->vcoord[2]*UINT_MAX;
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zld = zld + zd*xld/(float)(1<<16);
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#endif
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}
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if (recalcside & 2)
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{
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dx = (vrb->vcoord[0] - vrt->vcoord[0]);
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dy = (vrb->vcoord[1] - vrt->vcoord[1]);
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if (dy)
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xrd = (dx<<16) / dy;
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else
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xrd = 0;
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xr = (int)vrt->vcoord[0]<<16;
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}
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if (y + numspans >= th->vpheight)
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numspans = th->vpheight - y - 1;
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if (numspans <= 0)
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continue;
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vplout = th->vpcbuf + y * th->vpcstride; //this is a pointer to the left of the viewport buffer.
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interlace = ((y + th->interlaceline) % th->interlacemod);
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if (interlace)
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{
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if (interlace > numspans)
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{
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interlace = numspans;
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y+=interlace;
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}
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else
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{
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y+=interlace;
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numspans-=interlace;
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}
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xl += xld*interlace;
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xr += xrd*interlace;
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vplout += th->vpcstride*interlace;
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#ifdef SPAN_ST
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sl += sld*interlace;
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tl += tld*interlace;
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#endif
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#ifdef SPAN_Z
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zl += zld*interlace;
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#endif
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}
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for (; numspans > 0;
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numspans -= th->interlacemod
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,xl += xld*th->interlacemod
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,xr += xrd*th->interlacemod
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,vplout += th->vpcstride*th->interlacemod
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,y += th->interlacemod
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#ifdef SPAN_ST
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,sl += sld*th->interlacemod
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,tl += tld*th->interlacemod
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#endif
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#ifdef SPAN_Z
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,zl += zld*th->interlacemod
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#endif
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)
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{
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#ifdef SPAN_ST
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float s = sl;
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float t = tl;
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#endif
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#ifdef SPAN_Z
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unsigned int z = zl;
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unsigned int *restrict zb = th->vpdbuf + y * th->vpwidth + (xl>>16);
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#endif
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spanlen = (xr - xl)>>16;
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outbuf = vplout + (xl>>16);
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while(spanlen-->=0)
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{
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PLOT_PIXEL(*outbuf);
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outbuf++;
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#ifdef SPAN_ST
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s += sd;
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t += td;
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#endif
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#ifdef SPAN_Z
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z += zd;
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zb++;
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#endif
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}
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}
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}
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}
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#undef SPAN_ST
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#undef PLOT_PIXEL
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