X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?a=blobdiff_plain;ds=sidebyside;f=src%2Fpolytmpl.h;h=f36b288a1c24470d6bc743fe8b583d23f84af151;hb=b6c89d9ffbb08c5286448de4773290f0924a420b;hp=12df420c66295c1ec22768087cd52d1be309cead;hpb=1723e332319e7732473814dfc168a13d0bafccb4;p=dosdemo

diff --git a/src/polytmpl.h b/src/polytmpl.h
index 12df420..f36b288 100644
--- a/src/polytmpl.h
+++ b/src/polytmpl.h
@@ -69,7 +69,7 @@ static uint32_t SCANEDGE(struct pvertex *v0, struct pvertex *v1, struct pvertex
 
 void POLYFILL(struct pvertex *pv, int nverts)
 {
-	int i;
+	int i, winding;
 	int topidx = 0, botidx = 0, sltop = pfill_fb.height, slbot = 0;
 	struct pvertex *left, *right;
 	uint16_t color;
@@ -93,6 +93,12 @@ void POLYFILL(struct pvertex *pv, int nverts)
 		if(pv[i].y > pv[botidx].y) botidx = i;
 	}
 
+	winding = 0;
+	for(i=0; i<nverts; i++) {
+		int next = NEXTIDX(i);
+		winding += ((pv[next].x - pv[i].x) >> 4) * ((pv[next].y + pv[i].y) >> 4);
+	}
+
 	/* +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 +139,18 @@ 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) {
+				// clockwise
+				edge = y0 > y1 ? left : right;
+			} else {
+				// counter-clockwise
+				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;