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Fix software renderer ignoring texture in transparent render path

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The transparent code path skipped texture sampling entirely, producing
a solid colored rectangle instead of the textured shape. Move texture
sampling before the opaque/transparent branch so both paths get texel
color modulation, and use texel alpha for per-pixel transparency.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Christian Semmler 2026-03-16 12:54:17 -07:00
parent 09ed6edb3e
commit 176aef1d90
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GPG Key ID: 086DAA1360BEEE5C
1 changed files with 45 additions and 37 deletions
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82
miniwin/src/d3drm/backends/software/renderer.cpp
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@ -465,54 +465,62 @@ void Direct3DRMSoftwareRenderer::DrawTriangleProjected(
Uint8* pixelAddr = pixels + y * pitch + x * m_bytesPerPixel;
Uint32 finalColor;
if (appearance.color.a == 255) {
zref = z;
Uint8 alpha = appearance.color.a;
if (texels) {
// Perspective correct interpolate texture coords
float one_over_w = left.one_over_w + t * (right.one_over_w - left.one_over_w);
float u_over_w = left.u_over_w + t * (right.u_over_w - left.u_over_w);
float v_over_w = left.v_over_w + t * (right.v_over_w - left.v_over_w);
if (texels) {
// Perspective correct interpolate texture coords
float one_over_w = left.one_over_w + t * (right.one_over_w - left.one_over_w);
float u_over_w = left.u_over_w + t * (right.u_over_w - left.u_over_w);
float v_over_w = left.v_over_w + t * (right.v_over_w - left.v_over_w);
float inv_w = 1.0f / one_over_w;
float u = u_over_w * inv_w;
float v = v_over_w * inv_w;
float inv_w = 1.0f / one_over_w;
float u = u_over_w * inv_w;
float v = v_over_w * inv_w;
// Tile textures
u -= std::floor(u);
v -= std::floor(v);
// Tile textures
u -= std::floor(u);
v -= std::floor(v);
int texX = static_cast<int>(u * texWidthScale);
int texY = static_cast<int>(v * texHeightScale);
int texX = static_cast<int>(u * texWidthScale);
int texY = static_cast<int>(v * texHeightScale);
Uint8* texelAddr = texels + texY * texturePitch + texX * m_bytesPerPixel;
Uint8* texelAddr = texels + texY * texturePitch + texX * m_bytesPerPixel;
Uint32 texelColor;
switch (m_bytesPerPixel) {
case 1:
texelColor = *texelAddr;
break;
case 2:
texelColor = *(Uint16*) texelAddr;
break;
case 4:
texelColor = *(Uint32*) texelAddr;
break;
}
Uint8 tr, tg, tb, ta;
SDL_GetRGBA(texelColor, m_format, m_palette, &tr, &tg, &tb, &ta);
// Multiply vertex color by texel color
r = (r * tr + 127) / 255;
g = (g * tg + 127) / 255;
b = (b * tb + 127) / 255;
Uint32 texelColor;
switch (m_bytesPerPixel) {
case 1:
texelColor = *texelAddr;
break;
case 2:
texelColor = *(Uint16*) texelAddr;
break;
case 4:
texelColor = *(Uint32*) texelAddr;
break;
}
Uint8 tr, tg, tb, ta;
SDL_GetRGBA(texelColor, m_format, m_palette, &tr, &tg, &tb, &ta);
// Multiply vertex color by texel color
r = (r * tr + 127) / 255;
g = (g * tg + 127) / 255;
b = (b * tb + 127) / 255;
// Use texel alpha for per-pixel transparency
alpha = ta;
}
if (alpha == 0) {
continue;
}
if (alpha == 255) {
zref = z;
finalColor = SDL_MapRGBA(m_format, m_palette, r, g, b, 255);
}
else {
finalColor = BlendPixel(pixelAddr, r, g, b, appearance.color.a);
finalColor = BlendPixel(pixelAddr, r, g, b, alpha);
}
switch (m_bytesPerPixel) {