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fix triangle and quad spans applying pixels out of bounds

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This commit is contained in:
Colin James Wood 2026-05-08 18:20:47 +01:00
parent 95bfa196fd
commit b1a00ff996
1 changed files with 50 additions and 21 deletions
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71
src/external/rlsw.h vendored
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@ -5389,6 +5389,11 @@ static void SW_RASTER_TRIANGLE_SPAN(const sw_vertex_t *start, const sw_vertex_t
int xEnd = (int)end->position[0];
if (xStart == xEnd) return;
// Get the current row and skip if outside the framebuffer.
// Maybe this check is better suited elsewhere?
int y = (int)start->position[1];
if (y < 0 || y >= RLSW.colorBuffer->height) return;
// Compute the inverse horizontal distance along the X axis
float dxRcp = sw_rcp(end->position[0] - start->position[0]);
@ -5411,25 +5416,30 @@ static void SW_RASTER_TRIANGLE_SPAN(const sw_vertex_t *start, const sw_vertex_t
// Compute the subpixel distance to traverse before the first pixel
float xSubstep = 1.0f - sw_fract(start->position[0]);
// Initializing the interpolation starting values
float w = start->position[3] + dWdx*xSubstep;
// Intercept the span bounds to ensure we don't write before the framebuffer.
int xLoopStart = sw_clamp_int(xStart, 0, RLSW.colorBuffer->width - 1);
int dxStart = xLoopStart - xStart;
// Initializing the interpolation starting values.
// Also step further into them to move away from the colorbuffer edge.
float w = start->position[3] + dWdx*xSubstep + dWdx*dxStart;
float color[4] = {
start->color[0] + dCdx[0]*xSubstep,
start->color[1] + dCdx[1]*xSubstep,
start->color[2] + dCdx[2]*xSubstep,
start->color[3] + dCdx[3]*xSubstep
start->color[0] + dCdx[0]*xSubstep + dCdx[0]*dxStart,
start->color[1] + dCdx[1]*xSubstep + dCdx[1]*dxStart,
start->color[2] + dCdx[2]*xSubstep + dCdx[2]*dxStart,
start->color[3] + dCdx[3]*xSubstep + dCdx[3]*dxStart
};
#ifdef SW_ENABLE_DEPTH_TEST
float z = start->position[2] + dZdx*xSubstep;
float z = start->position[2] + dZdx*xSubstep + dZdx*dxStart;
#endif
#ifdef SW_ENABLE_TEXTURE
float u = start->texcoord[0] + dUdx*xSubstep;
float v = start->texcoord[1] + dVdx*xSubstep;
float u = start->texcoord[0] + dUdx*xSubstep + dUdx*dxStart;
float v = start->texcoord[1] + dVdx*xSubstep + dVdx*dxStart;
#endif
// Pre-calculate the starting pointers for the framebuffer row
int y = (int)start->position[1];
int baseOffset = y*RLSW.colorBuffer->width + xStart;
// Don't allow a y value outside the buffer.
int baseOffset = y*RLSW.colorBuffer->width + xLoopStart;
uint8_t *cPtr = (uint8_t *)(RLSW.colorBuffer->pixels) + baseOffset*SW_FRAMEBUFFER_COLOR_SIZE;
#ifdef SW_ENABLE_DEPTH_TEST
uint8_t *dPtr = (uint8_t *)(RLSW.depthBuffer->pixels) + baseOffset*SW_FRAMEBUFFER_DEPTH_SIZE;
@ -5437,12 +5447,14 @@ static void SW_RASTER_TRIANGLE_SPAN(const sw_vertex_t *start, const sw_vertex_t
#define SW_AFFINE_BLOCK 16
int x = xStart;
while (x < xEnd)
int x = xLoopStart;
// Prevent pixels from beyond the buffer from processing.
int xLoopEnd = sw_clamp_int(xEnd, 0, RLSW.colorBuffer->width - 1);
while (x < xLoopEnd)
{
// Clamp last block to remaining pixels
int blockEnd = x + SW_AFFINE_BLOCK;
if (blockEnd > xEnd) blockEnd = xEnd;
if (blockEnd > xLoopEnd) blockEnd = xLoopEnd;
float blockLenF = (float)(blockEnd - x);
float blockLenRcp = sw_rcp(blockLenF);
@ -5730,21 +5742,38 @@ static void SW_RASTER_QUAD(const sw_vertex_t *a, const sw_vertex_t *b,
uint8_t *dPixels = RLSW.depthBuffer->pixels;
#endif
for (int y = yMin; y < yMax; y++)
// Intercept the boundaries to stay within the framebuffer.
int yLoopMin = sw_clamp_int(yMin, 0, RLSW.colorBuffer->height - 1);
int yLoopMax = sw_clamp_int(yMax, 0, RLSW.colorBuffer->height - 1);
int xLoopMin = sw_clamp_int(xMin, 0, RLSW.colorBuffer->width - 1);
int xLoopMax = sw_clamp_int(xMax, 0, RLSW.colorBuffer->width - 1);
int dxMin = xLoopMin - xMin;
#if defined(SW_ENABLE_DEPTH_TEST) || defined(SW_ENABLE_TEXTURE)
int dyMin = yLoopMin - yMin;
#endif
for (int y = yLoopMin; y < yLoopMax; y++)
{
int baseOffset = y*stride + xMin;
int baseOffset = y*stride + xLoopMin;
uint8_t *cPtr = cPixels + baseOffset*SW_FRAMEBUFFER_COLOR_SIZE;
#ifdef SW_ENABLE_DEPTH_TEST
uint8_t *dPtr = dPixels + baseOffset*SW_FRAMEBUFFER_DEPTH_SIZE;
float z = zRow;
// Correct our start by how far we clipped outside the framebuffer.
float z = zRow + dZdy*dyMin;
#endif
#ifdef SW_ENABLE_TEXTURE
float u = uRow;
float v = vRow;
// Correct our start by how far we clipped outside the framebuffer.
float u = uRow + dUdy*dyMin;
float v = vRow + dVdy*dyMin;
#endif
float color[4] = { cRow[0], cRow[1], cRow[2], cRow[3] };
float color[4] = {
cRow[0] + dCdx[0]*dxMin,
cRow[1] + dCdx[1]*dxMin,
cRow[2] + dCdx[2]*dxMin,
cRow[3] + dCdx[3]*dxMin
};
for (int x = xMin; x < xMax; x++)
for (int x = xLoopMin; x < xLoopMax; x++)
{
float srcColor[4] = { color[0], color[1], color[2], color[3] };