Commit 111c70e141070cce5914b430564539e3d8505a35
2021-03-26T09:09:08
Use 64 bits precision to prevent overflow when interpolating color / texture with wide triangles
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diff --git a/src/render/software/SDL_triangle.c b/src/render/software/SDL_triangle.c
index 26e66a4..41fdebf 100644
--- a/src/render/software/SDL_triangle.c
+++ b/src/render/software/SDL_triangle.c
@@ -154,22 +154,23 @@ static void bounding_rect(const SDL_Point *a, const SDL_Point *b, const SDL_Poin
Uint8 *dptr = (Uint8 *) dst_ptr + x * dstbpp; \
+/* Use 64 bits precision to prevent overflow when interpolating color / texture with wide triangles */
#define TRIANGLE_GET_TEXTCOORD \
- int srcx = (w0 * s2s0_x + w1 * s2s1_x + s2_x_area.x) / area; \
- int srcy = (w0 * s2s0_y + w1 * s2s1_y + s2_x_area.y) / area; \
+ int srcx = ((Sint64)w0 * s2s0_x + (Sint64)w1 * s2s1_x + s2_x_area.x) / area; \
+ int srcy = ((Sint64)w0 * s2s0_y + (Sint64)w1 * s2s1_y + s2_x_area.y) / area; \
#define TRIANGLE_GET_MAPPED_COLOR \
- int r = (w0 * c0.r + w1 * c1.r + w2 * c2.r) / area; \
- int g = (w0 * c0.g + w1 * c1.g + w2 * c2.g) / area; \
- int b = (w0 * c0.b + w1 * c1.b + w2 * c2.b) / area; \
- int a = (w0 * c0.a + w1 * c1.a + w2 * c2.a) / area; \
+ int r = ((Sint64)w0 * c0.r + (Sint64)w1 * c1.r + (Sint64)w2 * c2.r) / area; \
+ int g = ((Sint64)w0 * c0.g + (Sint64)w1 * c1.g + (Sint64)w2 * c2.g) / area; \
+ int b = ((Sint64)w0 * c0.b + (Sint64)w1 * c1.b + (Sint64)w2 * c2.b) / area; \
+ int a = ((Sint64)w0 * c0.a + (Sint64)w1 * c1.a + (Sint64)w2 * c2.a) / area; \
int color = SDL_MapRGBA(format, r, g, b, a); \
#define TRIANGLE_GET_COLOR \
- int r = (w0 * c0.r + w1 * c1.r + w2 * c2.r) / area; \
- int g = (w0 * c0.g + w1 * c1.g + w2 * c2.g) / area; \
- int b = (w0 * c0.b + w1 * c1.b + w2 * c2.b) / area; \
- int a = (w0 * c0.a + w1 * c1.a + w2 * c2.a) / area; \
+ int r = ((Sint64)w0 * c0.r + (Sint64)w1 * c1.r + (Sint64)w2 * c2.r) / area; \
+ int g = ((Sint64)w0 * c0.g + (Sint64)w1 * c1.g + (Sint64)w2 * c2.g) / area; \
+ int b = ((Sint64)w0 * c0.b + (Sint64)w1 * c1.b + (Sint64)w2 * c2.b) / area; \
+ int a = ((Sint64)w0 * c0.a + (Sint64)w1 * c1.a + (Sint64)w2 * c2.a) / area; \
#define TRIANGLE_END_LOOP \