Port Antimony's render grid traversal algorithm
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Gustaf Alhäll
NepDisk
parent
34f7d76aeb
commit
cab86f9ad3
1 changed files with 61 additions and 141 deletions
202
src/p_maputl.c
202
src/p_maputl.c
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@ -1736,10 +1736,6 @@ static boolean P_TraverseIntercepts(traverser_t func, fixed_t maxfrac)
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boolean P_PathTraverse(fixed_t px1, fixed_t py1, fixed_t px2, fixed_t py2,
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INT32 flags, traverser_t trav)
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{
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fixed_t xt1, yt1, xt2, yt2;
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fixed_t xstep, ystep, partialx, partialy, xintercept, yintercept;
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INT32 mapx, mapy, mapxstep, mapystep, count;
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validcount++;
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intercept_p = intercepts;
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@ -1756,170 +1752,94 @@ boolean P_PathTraverse(fixed_t px1, fixed_t py1, fixed_t px2, fixed_t py2,
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px1 -= bmaporgx;
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py1 -= bmaporgy;
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xt1 = (unsigned)px1>>MAPBLOCKSHIFT;
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yt1 = (unsigned)py1>>MAPBLOCKSHIFT;
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px2 -= bmaporgx;
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py2 -= bmaporgy;
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xt2 = (unsigned)px2>>MAPBLOCKSHIFT;
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yt2 = (unsigned)py2>>MAPBLOCKSHIFT;
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if (xt2 > xt1)
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// blockmap traversal algorithm ported from antimony
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int gridpos_x = px1 >> MAPBLOCKSHIFT;
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int gridpos_y = py1 >> MAPBLOCKSHIFT;
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if (flags & PT_ADDLINES)
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if (!P_BlockLinesIterator(gridpos_x, gridpos_y, PIT_AddLineIntercepts))
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return false; // early out
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if (flags & PT_ADDTHINGS)
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if (!P_BlockThingsIterator(gridpos_x, gridpos_y, PIT_AddThingIntercepts))
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return false; // early out
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int endpos_x = px2 >> MAPBLOCKSHIFT;
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int endpos_y = py2 >> MAPBLOCKSHIFT;
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if (gridpos_x == endpos_x && gridpos_y == endpos_y)
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return P_TraverseIntercepts(trav, FRACUNIT);
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fixed_t pos_x = px1;
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fixed_t pos_y = py1;
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fixed_t dist_x = px2 - px1;
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fixed_t dist_y = py2 - py1;
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int dir_x = dist_x < 0 ? -1 : 1;
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int dir_y = dist_y < 0 ? -1 : 1;
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fixed_t delta_x;
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fixed_t delta_y;
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// special cases for 0 to avoid crashes
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if (dist_y == 0)
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{
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mapxstep = 1;
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partialx = FRACUNIT - ((px1>>MAPBTOFRAC) & FRACMASK);
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ystep = FixedDiv(py2 - py1, abs(px2 - px1));
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delta_x = INT32_MAX;
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delta_y = 0;
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}
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else if (xt2 < xt1)
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else if (dist_x == 0)
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{
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mapxstep = -1;
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partialx = (px1>>MAPBTOFRAC) & FRACMASK;
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ystep = FixedDiv(py2 - py1, abs(px2 - px1));
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delta_x = 0;
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delta_y = INT32_MAX;
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}
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else
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{
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mapxstep = 0;
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partialx = FRACUNIT;
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ystep = 256*FRACUNIT;
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delta_x = FixedDiv2(dist_x, abs(dist_y));
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delta_y = FixedDiv2(dist_y, abs(dist_x));
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}
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yintercept = (py1>>MAPBTOFRAC) + FixedMul(partialx, ystep);
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while (gridpos_x >= 0 && gridpos_y >= 0 && gridpos_x < bmapwidth && gridpos_y < bmapheight)
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{
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fixed_t hitx_x;
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if (dir_x > 0)
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hitx_x = (gridpos_x+1) << MAPBLOCKSHIFT;
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else
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hitx_x = gridpos_x << MAPBLOCKSHIFT;
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if (yt2 > yt1)
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{
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mapystep = 1;
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partialy = FRACUNIT - ((py1>>MAPBTOFRAC) & FRACMASK);
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xstep = FixedDiv(px2 - px1, abs(py2 - py1));
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}
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else if (yt2 < yt1)
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{
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mapystep = -1;
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partialy = (py1>>MAPBTOFRAC) & FRACMASK;
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xstep = FixedDiv(px2 - px1, abs(py2 - py1));
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}
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else
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{
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mapystep = 0;
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partialy = FRACUNIT;
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xstep = 256*FRACUNIT;
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}
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xintercept = (px1>>MAPBTOFRAC) + FixedMul(partialy, xstep);
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fixed_t hity_y;
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if (dir_y > 0)
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hity_y = (gridpos_y+1) << MAPBLOCKSHIFT;
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else
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hity_y = gridpos_y << MAPBLOCKSHIFT;
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// [RH] Fix for traces that pass only through blockmap corners. In that case,
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// xintercept and yintercept can both be set ahead of mapx and mapy, so the
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// for loop would never advance anywhere.
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if (abs(xstep) == FRACUNIT && abs(ystep) == FRACUNIT)
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{
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if (ystep < 0)
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hitx_x -= pos_x;
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hity_y -= pos_y;
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fixed_t hitx_y = FixedMul(delta_y, abs(hitx_x));
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fixed_t hity_x = FixedMul(delta_x, abs(hity_y));
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if (FixedMul(hitx_x, hitx_x) + FixedMul(hitx_y, hitx_y) > FixedMul(hity_x, hity_x) + FixedMul(hity_y, hity_y))
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{
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partialx = FRACUNIT - partialx;
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gridpos_y += dir_y;
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pos_x += hity_x;
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pos_y += hity_y;
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}
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if (xstep < 0)
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else
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{
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partialy = FRACUNIT - partialy;
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gridpos_x += dir_x;
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pos_x += hitx_x;
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pos_y += hitx_y;
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}
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if (partialx == partialy)
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{
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xintercept = xt1 << FRACBITS;
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yintercept = yt1 << FRACBITS;
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}
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}
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// Step through map blocks.
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// Count is present to prevent a round off error
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// from skipping the break.
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mapx = xt1;
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mapy = yt1;
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for (count = 0; count < 100; count++)
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{
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if (flags & PT_ADDLINES)
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{
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P_BlockLinesIterator(mapx, mapy, PIT_AddLineIntercepts);
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}
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if (!P_BlockLinesIterator(gridpos_x, gridpos_y, PIT_AddLineIntercepts))
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return false; // early out
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if (flags & PT_ADDTHINGS)
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{
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P_BlockThingsIterator(mapx, mapy, PIT_AddThingIntercepts);
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}
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// both coordinates reached the end, so end the traversing.
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if ((mapxstep | mapystep) == 0)
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{
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if (!P_BlockThingsIterator(gridpos_x, gridpos_y, PIT_AddThingIntercepts))
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return false; // early out
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if (gridpos_x == endpos_x && gridpos_y == endpos_y)
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break;
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}
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// [RH] Handle corner cases properly instead of pretending they don't exist.
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switch ( (((yintercept >> FRACBITS) == mapy) << 1) | ((xintercept >> FRACBITS) == mapx) )
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{
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case 0: // neither xintercept nor yintercept match!
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{
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count = 100; // Stop traversing, because somebody screwed up.
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break;
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}
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case 1: // xintercept matches
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{
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xintercept += xstep;
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mapy += mapystep;
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if (mapy == yt2)
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{
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mapystep = 0;
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}
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break;
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}
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case 2: // yintercept matches
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{
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yintercept += ystep;
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mapx += mapxstep;
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if (mapx == xt2)
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{
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mapxstep = 0;
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}
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break;
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}
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case 3: // xintercept and yintercept both match
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{
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// The trace is exiting a block through its corner. Not only does the block
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// being entered need to be checked (which will happen when this loop
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// continues), but the other two blocks adjacent to the corner also need to
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// be checked.
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if (flags & PT_ADDLINES)
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{
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P_BlockLinesIterator(mapx + mapxstep, mapy, PIT_AddLineIntercepts);
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P_BlockLinesIterator(mapx, mapy + mapystep, PIT_AddLineIntercepts);
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}
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if (flags & PT_ADDTHINGS)
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{
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P_BlockThingsIterator(mapx + mapxstep, mapy, PIT_AddThingIntercepts);
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P_BlockThingsIterator(mapx, mapy + mapystep, PIT_AddThingIntercepts);
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}
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xintercept += xstep;
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yintercept += ystep;
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mapx += mapxstep;
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mapy += mapystep;
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if (mapx == xt2)
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{
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mapxstep = 0;
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}
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if (mapy == yt2)
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{
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mapystep = 0;
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}
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break;
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}
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}
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}
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// Go through the sorted list
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return P_TraverseIntercepts(trav, FRACUNIT);
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}
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// =========================================================================
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// BLOCKMAP ITERATORS
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// =========================================================================
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