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#include "TMapare.h"
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TMapare::TMapare(int *iscreen, int iscreenwidth, int iscreenheight)
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{
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screen=(int*)iscreen;
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screenwidth=iscreenwidth; |
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screenheight=iscreenheight; |
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}
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TMapare::~TMapare(){}
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// Texturemapper with full perspective correction, subpixels and subtexels, |
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// uses floats all the way through |
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void TMapare::drawtpolyperspsubtri(TPolytri *poly) |
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{ |
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float x1, y1, x2, y2, x3, y3; |
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float iz1, uiz1, viz1, iz2, uiz2, viz2, iz3, uiz3, viz3; |
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float dxdy1, dxdy2, dxdy3; |
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float tempf; |
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float denom; |
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float dy; |
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int y1i, y2i, y3i; |
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int side; |
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// Shift XY coordinate system (+0.5, +0.5) to match the subpixeling |
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// technique |
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x1 = (float) poly->x1 + 0.5f; |
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y1 = (float) poly->y1 + 0.5f; |
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x2 = (float) poly->x2 + 0.5f; |
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y2 = (float) poly->y2 + 0.5f; |
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x3 = (float) poly->x3 + 0.5f; |
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y3 = (float) poly->y3 + 0.5f; |
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// Calculate alternative 1/Z, U/Z and V/Z values which will be |
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// interpolated |
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iz1 = 1 / poly->z1; |
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iz2 = 1 / poly->z2; |
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iz3 = 1 / poly->z3; |
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uiz1 = poly->u1 * iz1; |
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viz1 = poly->v1 * iz1; |
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uiz2 = poly->u2 * iz2; |
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viz2 = poly->v2 * iz2; |
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uiz3 = poly->u3 * iz3; |
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viz3 = poly->v3 * iz3; |
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texture = poly->texture; |
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// Sort the vertices in ascending Y order |
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#define swapfloat(x, y) tempf = x; x = y; y = tempf; |
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if (y1 > y2) |
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{ |
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swapfloat(x1, x2); |
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swapfloat(y1, y2); |
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swapfloat(iz1, iz2); |
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swapfloat(uiz1, uiz2); |
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swapfloat(viz1, viz2); |
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} |
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if (y1 > y3) |
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{ |
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swapfloat(x1, x3); |
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swapfloat(y1, y3); |
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swapfloat(iz1, iz3); |
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swapfloat(uiz1, uiz3); |
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swapfloat(viz1, viz3); |
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} |
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if (y2 > y3) |
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{ |
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swapfloat(x2, x3); |
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swapfloat(y2, y3); |
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swapfloat(iz2, iz3); |
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swapfloat(uiz2, uiz3); |
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swapfloat(viz2, viz3); |
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} |
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#undef swapfloat |
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y1i = (int) y1; |
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y2i = (int) y2; |
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y3i = (int) y3; |
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// Skip poly if it's too thin to cover any pixels at all |
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if (y1i == y2i == y3i || (int) x1 == (int) x2 == (int) x3) |
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{
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return; |
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}
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// Calculate horizontal and vertical increments for UV axes (these |
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// calcs are certainly not optimal, although they're stable |
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// (handles any dy being 0) |
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denom = ((x3 - x1) * (y2 - y1) - (x2 - x1) * (y3 - y1)); |
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if (!denom) // Skip poly if it's an infinitely thin line |
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{
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return; |
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}
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denom = 1 / denom; // Reciprocal for speeding up |
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dizdx = ((iz3 - iz1) * (y2 - y1) - (iz2 - iz1) * (y3 - y1)) * denom; |
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duizdx = ((uiz3 - uiz1) * (y2 - y1) - (uiz2 - uiz1) * (y3 - y1)) * denom; |
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dvizdx = ((viz3 - viz1) * (y2 - y1) - (viz2 - viz1) * (y3 - y1)) * denom; |
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dizdy = ((iz2 - iz1) * (x3 - x1) - (iz3 - iz1) * (x2 - x1)) * denom; |
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duizdy = ((uiz2 - uiz1) * (x3 - x1) - (uiz3 - uiz1) * (x2 - x1)) * denom; |
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dvizdy = ((viz2 - viz1) * (x3 - x1) - (viz3 - viz1) * (x2 - x1)) * denom; |
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// Calculate X-slopes along the edges |
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if (y2 > y1) |
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dxdy1 = (x2 - x1) / (y2 - y1); |
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if (y3 > y1) |
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dxdy2 = (x3 - x1) / (y3 - y1); |
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if (y3 > y2) |
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dxdy3 = (x3 - x2) / (y3 - y2); |
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// Determine which side of the poly the longer edge is on |
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side = dxdy2 > dxdy1; |
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if (y1 == y2) |
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side = x1 > x2; |
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if (y2 == y3) |
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side = x3 > x2; |
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if (!side) // Longer edge is on the left side |
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{ |
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// Calculate slopes along left edge |
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dxdya = dxdy2; |
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dizdya = dxdy2 * dizdx + dizdy; |
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duizdya = dxdy2 * duizdx + duizdy; |
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dvizdya = dxdy2 * dvizdx + dvizdy; |
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// Perform subpixel pre-stepping along left edge |
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dy = 1 - (y1 - y1i); |
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xa = x1 + dy * dxdya; |
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iza = iz1 + dy * dizdya; |
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uiza = uiz1 + dy * duizdya; |
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viza = viz1 + dy * dvizdya; |
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if (y1i < y2i) // Draw upper segment if possibly visible |
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{ |
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// Set right edge X-slope and perform subpixel pre- |
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// stepping |
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xb = x1 + dy * dxdy1; |
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dxdyb = dxdy1; |
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drawtpolyperspsubtriseg(y1i, y2i); |
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}
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if (y2i < y3i) // Draw lower segment if possibly visible |
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{ |
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// Set right edge X-slope and perform subpixel pre- |
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// stepping |
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xb = x2 + (1 - (y2 - y2i)) * dxdy3; |
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dxdyb = dxdy3; |
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drawtpolyperspsubtriseg(y2i, y3i); |
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} |
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} |
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else // Longer edge is on the right side |
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{ |
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// Set right edge X-slope and perform subpixel pre-stepping |
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dxdyb = dxdy2; |
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dy = 1 - (y1 - y1i); |
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xb = x1 + dy * dxdyb; |
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if (y1i < y2i) // Draw upper segment if possibly visible |
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{ |
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// Set slopes along left edge and perform subpixel |
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// pre-stepping |
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dxdya = dxdy1; |
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dizdya = dxdy1 * dizdx + dizdy; |
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duizdya = dxdy1 * duizdx + duizdy; |
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dvizdya = dxdy1 * dvizdx + dvizdy; |
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xa = x1 + dy * dxdya; |
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iza = iz1 + dy * dizdya; |
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uiza = uiz1 + dy * duizdya; |
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viza = viz1 + dy * dvizdya; |
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drawtpolyperspsubtriseg(y1i, y2i); |
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} |
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if (y2i < y3i) // Draw lower segment if possibly visible |
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{ |
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// Set slopes along left edge and perform subpixel |
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// pre-stepping |
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dxdya = dxdy3; |
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dizdya = dxdy3 * dizdx + dizdy; |
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duizdya = dxdy3 * duizdx + duizdy; |
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dvizdya = dxdy3 * dvizdx + dvizdy; |
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dy = 1 - (y2 - y2i); |
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xa = x2 + dy * dxdya; |
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iza = iz2 + dy * dizdya; |
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uiza = uiz2 + dy * duizdya; |
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viza = viz2 + dy * dvizdya; |
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drawtpolyperspsubtriseg(y2i, y3i); |
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} |
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} |
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} |
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void TMapare::drawtpolyperspsubtriseg(int y1, int y2) |
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{ |
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int *scr; |
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int x1, x2; |
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float z, u, v, dx; |
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float iz, uiz, viz; |
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while (y1 < y2) // Loop through all lines in the segment |
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{ |
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x1 = (int) xa; |
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x2 = (int) xb; |
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// Perform subtexel pre-stepping on 1/Z, U/Z and V/Z |
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dx = 1 - (xa - x1); |
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iz = iza + dx * dizdx; |
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uiz = uiza + dx * duizdx; |
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viz = viza + dx * dvizdx; |
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scr = &screen[(screenheight-y1) * screenwidth + x1]; |
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while (x1++ < x2) // Draw horizontal line |
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{ |
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// Calculate U and V from 1/Z, U/Z and V/Z |
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z = 1 / iz; |
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u = uiz * z; |
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v = viz * z; |
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// Copy pixel from texture to screen |
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*(scr++) = texture[((((int) v) & 0xff) << 8) + (((int) u) & 0xff)]; |
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// Step 1/Z, U/Z and V/Z horizontally |
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iz += dizdx; |
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uiz += duizdx; |
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viz += dvizdx; |
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} |
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// Step along both edges |
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xa += dxdya; |
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xb += dxdyb; |
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iza += dizdya; |
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uiza += duizdya; |
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viza += dvizdya; |
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y1++; |
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} |
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} |
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