M CHANGES → CHANGES

@@ -3,6 +3,7 @@ Features:
  - DS GX: Toon shading
 Bugfixes:
  - DS GX: Fix vertex texture transformation (fixes mgba.io/i/702)
+ - DS GX: Automatically normalize winding culling calculations (fixes mgba.io/i/699)
 Misc:
  - DS GX: Clean up and unify texture mapping
 

M include/mgba-util/math.h → include/mgba-util/math.h

@@ -53,6 +53,51 @@ return table[bits] + 24;
 #endif
 }
 
+static inline unsigned clz64(uint64_t bits) {
+#if defined(__GNUC__) || __clang__
+	if (!bits) {
+		return 64;
+	}
+	return __builtin_clzll(bits);
+#else
+	static const int table[256] = {
+		8, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4,
+		3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
+		2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+		2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+		1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+	};
+
+	if (bits & 0xFF00000000000000) {
+		return table[bits >> 56];
+	} else if (bits & 0x00FF000000000000) {
+		return table[bits >> 48] + 8;
+	} else if (bits & 0x0000FF0000000000) {
+		return table[bits >> 40] + 16;
+	} else if (bits & 0x000000FF00000000) {
+		return table[bits >> 32] + 24;
+	} else if (bits & 0x00000000FF000000) {
+		return table[bits >> 24] + 32;
+	} else if (bits & 0x0000000000FF0000) {
+		return table[bits >> 16] + 40;
+	} else if (bits & 0x000000000000FF00) {
+		return table[bits >> 8] + 48;
+	}
+	return table[bits] + 56;
+#endif
+}
+
 static inline uint32_t toPow2(uint32_t bits) {
 	if (!bits) {
 		return 0;

M src/ds/gx.c → src/ds/gx.c

@@ -7,6 +7,7 @@ #include <mgba/internal/ds/gx.h>
 
 #include <mgba/internal/ds/ds.h>
 #include <mgba/internal/ds/io.h>
+#include <mgba-util/math.h>
 
 mLOG_DEFINE_CATEGORY(DS_GX, "DS GX", "ds.gx");
 
@@ -237,6 +238,7 @@ int64_t nx = 0;
 		int64_t ny = 0;
 		int64_t nz = 0;
 		int64_t dot = 0;
+		int rank = 30;
 		for (v = 0; v < poly->verts; ++v) {
 			struct DSGXVertex* v0 = &gx->pendingVertices[poly->vertIds[v]];
 			struct DSGXVertex* v1;
@@ -251,9 +253,28 @@ } else {
 				v1 = &gx->pendingVertices[poly->vertIds[v + 1 - poly->verts]];
 				v2 = &gx->pendingVertices[poly->vertIds[v + 2 - poly->verts]];
 			}
-			nx = ((int64_t) v0->viewCoord[1] * v2->viewCoord[3] - (int64_t) v0->viewCoord[3] * v2->viewCoord[1]) >> 24;
-			ny = ((int64_t) v0->viewCoord[3] * v2->viewCoord[0] - (int64_t) v0->viewCoord[0] * v2->viewCoord[3]) >> 24;
-			nz = ((int64_t) v0->viewCoord[0] * v2->viewCoord[1] - (int64_t) v0->viewCoord[1] * v2->viewCoord[0]) >> 24;
+			nx = ((int64_t) v0->viewCoord[1] * v2->viewCoord[3] - (int64_t) v0->viewCoord[3] * v2->viewCoord[1]);
+			ny = ((int64_t) v0->viewCoord[3] * v2->viewCoord[0] - (int64_t) v0->viewCoord[0] * v2->viewCoord[3]);
+			nz = ((int64_t) v0->viewCoord[0] * v2->viewCoord[1] - (int64_t) v0->viewCoord[1] * v2->viewCoord[0]);
+			int rx = 64 - clz64(nx >= 0 ? nx : -nx);
+			int ry = 64 - clz64(ny >= 0 ? ny : -ny);
+			int rz = 64 - clz64(nz >= 0 ? nz : -nz);
+			if (ry > rx) {
+				rx = ry;
+			}
+			if (rz > rx) {
+				rx = rz;
+			}
+			if (rx > 30) {
+				nx >>= rx - 30;
+				ny >>= rx - 30;
+				nz >>= rx - 30;
+			}
+			if (rx > rank) {
+				dot >>= rx - rank;
+				rank = rx;
+			}
+
 			dot += nx * v1->viewCoord[0] + ny * v1->viewCoord[1] + nz * v1->viewCoord[3];
 		}
 		if (!DSGXPolygonAttrsIsBackFace(poly->polyParams) && dot < 0) {