From 111c70e141070cce5914b430564539e3d8505a35 Mon Sep 17 00:00:00 2001 From: Sylvain Date: Fri, 26 Mar 2021 09:09:08 +0100 Subject: [PATCH] Use 64 bits precision to prevent overflow when interpolating color / texture with wide triangles --- src/render/software/SDL_triangle.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) diff --git a/src/render/software/SDL_triangle.c b/src/render/software/SDL_triangle.c index 26e66a458..41fdebfb7 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 \