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Fix particle glow transparency for textures without alpha

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Kelsi 2026-02-14 22:32:12 -08:00
parent a2c049b00b
commit 630019aea9
3 changed files with 29 additions and 9 deletions
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2
include/rendering/m2_renderer.hpp
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@ -360,8 +360,10 @@ private:
GLuint id = 0;
size_t approxBytes = 0;
uint64_t lastUse = 0;
bool hasAlpha = true;
};
std::unordered_map<std::string, TextureCacheEntry> textureCache;
std::unordered_map<GLuint, bool> textureHasAlphaById_;
size_t textureCacheBytes_ = 0;
uint64_t textureCacheCounter_ = 0;
size_t textureCacheBudgetBytes_ = 2048ull * 1024 * 1024; // Default, overridden at init

9
src/pipeline/blp_loader.cpp
View file

@ -167,13 +167,8 @@ BLPImage BLPLoader::loadBLP2(const uint8_t* data, size_t size) {
return BLPImage();
}
// DXT1 with alphaDepth=0 has no meaningful alpha channel, but the DXT1
// color-key mode can produce alpha=0 pixels. Force all alpha to 255.
if (header->alphaDepth == 0) {
for (int i = 0; i < pixelCount; i++) {
image.data[i * 4 + 3] = 255;
}
}
// Note: DXT1 may encode 1-bit transparency via the color-key mode (c0 <= c1).
// Do not override alpha based on alphaDepth; preserve whatever the DXT decompressor produced.
return image;
}

27
src/rendering/m2_renderer.cpp
View file

@ -659,6 +659,7 @@ void M2Renderer::shutdown() {
textureCache.clear();
textureCacheBytes_ = 0;
textureCacheCounter_ = 0;
textureHasAlphaById_.clear();
if (whiteTexture != 0) {
glDeleteTextures(1, &whiteTexture);
whiteTexture = 0;
@ -2420,8 +2421,19 @@ void M2Renderer::renderM2Particles(const glm::mat4& view, const glm::mat4& proj)
for (auto& [key, group] : groups) {
if (group.vertexData.empty()) continue;
// Set blend mode
if (group.blendType == 4) {
// Set blend mode. Many classic glow textures use a black background with no alpha,
// and expect additive blending so black contributes nothing.
bool texHasAlpha = true;
if (auto it = textureHasAlphaById_.find(group.texture); it != textureHasAlphaById_.end()) {
texHasAlpha = it->second;
}
uint8_t blendType = group.blendType;
if ((blendType == 1 || blendType == 2) && !texHasAlpha) {
blendType = 4; // Treat as additive fallback
}
if (blendType == 3 || blendType == 4) {
glBlendFunc(GL_SRC_ALPHA, GL_ONE); // Additive
} else {
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); // Alpha
@ -2717,6 +2729,15 @@ GLuint M2Renderer::loadTexture(const std::string& path) {
return whiteTexture;
}
// Track whether the texture actually uses alpha (any pixel with alpha < 255).
bool hasAlpha = false;
for (size_t i = 3; i < blp.data.size(); i += 4) {
if (blp.data[i] != 255) {
hasAlpha = true;
break;
}
}
GLuint textureID;
glGenTextures(1, &textureID);
glBindTexture(GL_TEXTURE_2D, textureID);
@ -2738,9 +2759,11 @@ GLuint M2Renderer::loadTexture(const std::string& path) {
e.id = textureID;
size_t base = static_cast<size_t>(blp.width) * static_cast<size_t>(blp.height) * 4ull;
e.approxBytes = base + (base / 3);
e.hasAlpha = hasAlpha;
e.lastUse = ++textureCacheCounter_;
textureCacheBytes_ += e.approxBytes;
textureCache[key] = e;
textureHasAlphaById_[textureID] = hasAlpha;
LOG_DEBUG("M2: Loaded texture: ", path, " (", blp.width, "x", blp.height, ")");
return textureID;