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[rlsw][SEGFAULT] Fix triangle and quad spans applying pixels out of bounds (#5849)

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* fix triangle and quad spans applying pixels out of bounds

* remove off by one errors on x/y LoopMax

* apply the RASTER_QUAD offset at the loop start so it increments correctly

* fix missing endif

* remove include guard to allow dyMin usage

* early exit if nothing to draw on a span

* incorporate dxStart into xSubstep to make xOffset calculate a single time

* remove ghost comment

* early exit for quads, with a float cast on the left and top distance calculation

* remove duplicate xLoopEnd
This commit is contained in:
Colin James Wood
2026-05-20 08:12:20 +01:00
committed by GitHub
parent b48933b096
commit 7d5b61ce01
1 changed files with 66 additions and 18 deletions
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84
src/external/rlsw.h vendored
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@@ -5385,6 +5385,17 @@ 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;
// Intercept the span bounds to ensure we don't write before the framebuffer.
int xLoopStart = (xStart >= 0)? xStart : 0;
int xLoopEnd = (xEnd <= RLSW.colorBuffer->width)? xEnd : RLSW.colorBuffer->width;
// Nothing to draw.
if (xLoopStart >= xLoopEnd) 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]);
@@ -5405,27 +5416,29 @@ static void SW_RASTER_TRIANGLE_SPAN(const sw_vertex_t *start, const sw_vertex_t
#endif
// Compute the subpixel distance to traverse before the first pixel
// Also step further into them to move away from the colorbuffer edge.
float xSubstep = 1.0f - sw_fract(start->position[0]);
float dxStart = (float)(xLoopStart - xStart);
float xOffset = xSubstep + dxStart;
// Initializing the interpolation starting values
float w = start->position[3] + dWdx*xSubstep;
// Initializing the interpolation starting values.
float w = start->position[3] + dWdx*xOffset;
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]*xOffset,
start->color[1] + dCdx[1]*xOffset,
start->color[2] + dCdx[2]*xOffset,
start->color[3] + dCdx[3]*xOffset
};
#ifdef SW_ENABLE_DEPTH_TEST
float z = start->position[2] + dZdx*xSubstep;
float z = start->position[2] + dZdx*xOffset;
#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*xOffset;
float v = start->texcoord[1] + dVdx*xOffset;
#endif
// Pre-calculate the starting pointers for the framebuffer row
int y = (int)start->position[1];
int baseOffset = y*RLSW.colorBuffer->width + xStart;
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;
@@ -5433,12 +5446,12 @@ 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;
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);
@@ -5673,6 +5686,14 @@ static void SW_RASTER_QUAD(const sw_vertex_t *a, const sw_vertex_t *b,
int xMax = (int)br->position[0];
int yMax = (int)br->position[1];
// Exit early if no pixels to draw. Use these later for loop boundaries
int yLoopMin = (yMin >= 0)? yMin : 0;
int xLoopMin = (xMin >= 0)? xMin : 0;
int yLoopMax = (yMax <= RLSW.colorBuffer->height)? yMax : RLSW.colorBuffer->height;
int xLoopMax = (xMax <= RLSW.colorBuffer->width)? xMax : RLSW.colorBuffer->width;
if (yLoopMin >= yLoopMax || xLoopMin >= xLoopMax) return;
float w = (float)(xMax - xMin);
float h = (float)(yMax - yMin);
if ((w <= 0) || (h <= 0)) return;
@@ -5726,21 +5747,44 @@ 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++)
// Calculate the distance the in-bounds boundary is from the quad's edges, only on the left and top.
float dxMin = (float)(xLoopMin - xMin);
float dyMin = (float)(yLoopMin - yMin);
// Correct our start by how far we clipped outside the framebuffer.
cRow[0] += dCdx[0]*dxMin + dCdy[0]*dyMin;
cRow[1] += dCdx[1]*dxMin + dCdy[1]*dyMin;
cRow[2] += dCdx[2]*dxMin + dCdy[2]*dyMin;
cRow[3] += dCdx[3]*dxMin + dCdy[3]*dyMin;
#ifdef SW_ENABLE_DEPTH_TEST
zRow += dZdy*dyMin + dZdx*dxMin;
#endif
#ifdef SW_ENABLE_TEXTURE
uRow += dUdy*dyMin + dUdx*dxMin;
vRow += dVdy*dyMin + dVdx*dxMin;
#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;
// Copy the cursors so we increment them ourselves without destroying the offset maths.
float z = zRow;
#endif
#ifdef SW_ENABLE_TEXTURE
float u = uRow;
float v = vRow;
#endif
float color[4] = { cRow[0], cRow[1], cRow[2], cRow[3] };
float color[4] = {
cRow[0],
cRow[1],
cRow[2],
cRow[3]
};
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] };
@@ -5779,6 +5823,7 @@ static void SW_RASTER_QUAD(const sw_vertex_t *a, const sw_vertex_t *b,
#ifdef SW_ENABLE_DEPTH_TEST
discard:
#endif
// We move one pixel over without touching the original "start offset"
color[0] += dCdx[0];
color[1] += dCdx[1];
color[2] += dCdx[2];
@@ -5801,6 +5846,9 @@ static void SW_RASTER_QUAD(const sw_vertex_t *a, const sw_vertex_t *b,
cPtr += SW_FRAMEBUFFER_COLOR_SIZE;
}
// The for loop is clamped to the right side of the screen.
// However, these cursor start vars are still on the left.
// That's fine. We just need to advance to the next row.
cRow[0] += dCdy[0];
cRow[1] += dCdy[1];
cRow[2] += dCdy[2];