reflection

[dosrtxon] / src / polytmpl.h

diff --git a/src/polytmpl.h b/src/polytmpl.h
index 12df420..d61ac8e 100644 (file)
--- a/src/polytmpl.h
+++ b/src/polytmpl.h
@@ -93,6 +93,12 @@ void POLYFILL(struct pvertex *pv, int nverts)
                if(pv[i].y > pv[botidx].y) botidx = i;
        }
 
+       int winding = 0;
+       for(i=0; i<nverts; i++) {
+               int next = NEXTIDX(i);
+               winding += (pv[next].x - pv[i].x) * (pv[next].y + pv[i].y);
+       }
+
        /* +1 to avoid crashing due to off-by-one rounding errors in the rasterization */
        left = alloca((pfill_fb.height + 1) * sizeof *left);
        right = alloca((pfill_fb.height + 1) * sizeof *right);
@@ -133,9 +139,16 @@ void POLYFILL(struct pvertex *pv, int nverts)
                                if(idx < sltop) sltop = idx;
                        /*}*/
                } else {
-                       struct pvertex *edge = y0 > y1 ? left : right;
-                       uint32_t res = SCANEDGE(pv + i, pv + next, edge);
-                       uint32_t tmp = (res >> 16) & 0xffff;
+                       struct pvertex *edge;
+                       uint32_t res, tmp;
+
+                       if(winding < 0) {
+                               edge = y0 > y1 ? left : right;
+                       } else {
+                               edge = y0 > y1 ? right : left;
+                       }
+                       res = SCANEDGE(pv + i, pv + next, edge);
+                       tmp = (res >> 16) & 0xffff;
                        if(tmp > slbot) slbot = tmp;
                        if((tmp = res & 0xffff) < sltop) {
                                sltop = tmp;