Sanitize NaN/Inf in env cubemap and tonemap to stop one-frame black flashes

gl/cubemap.cpp

@@ -21,6 +21,11 @@ void gl::cubemap::alloc(GLint format, int width, int height, GLenum components,
 	for (GLuint tgt = GL_TEXTURE_CUBE_MAP_POSITIVE_X; tgt <= GL_TEXTURE_CUBE_MAP_NEGATIVE_Z; tgt++)
 		glTexImage2D(tgt, 0, format, width, height, 0, components, type, nullptr);
 
+	// make the cubemap sample-complete with no mipmaps required.
+	// generate_mipmaps() will later override MIN_FILTER once mips actually exist.
+	glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+	glTexParameteri(GL_TEXTURE_CUBE_MAP, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+
 	glBindTexture(GL_TEXTURE_CUBE_MAP, 0);
 }
 

shaders/envmapping.glsl

@@ -8,6 +8,14 @@ vec3 envmap_color( vec3 normal )
 	vec3 refvec = reflect(f_pos.xyz, normal); // view space
 	refvec = vec3(inv_view * vec4(refvec, 0.0)); // world space
 	vec3 envcolor = texture(envmap, refvec).rgb;
+	// Sanitize. The env cubemap can briefly contain NaN/Inf after a
+	// reflection-pass regeneration (m_empty_cubemap was bound during the
+	// face render and on NVIDIA can sample as undefined). Without this
+	// guard, a single bad texel propagates through env_reflection in
+	// apply_lights() and produces one-frame black flashes on glossy
+	// (esp. specgloss) surfaces.
+	if (any(isnan(envcolor)) || any(isinf(envcolor))) envcolor = vec3(0.0);
+	envcolor = max(envcolor, vec3(0.0));
 #else
 	vec3 envcolor = vec3(0.5);
 #endif
@@ -21,7 +29,12 @@ vec3 envmap_color_lod(vec3 fragnormal, float lod)
 #if ENVMAP_ENABLED
     vec3 refvec = reflect(f_pos.xyz, fragnormal); // view space — matches envmap_color exactly
     refvec = vec3(inv_view * vec4(refvec, 0.0));  // world space — was missing
-    return textureLod(envmap, refvec, lod).rgb;
+    vec3 envcolor = textureLod(envmap, refvec, lod).rgb;
+    // See envmap_color() above — same NaN/Inf sanitize, also needed here
+    // because mipmap generation propagates a single NaN texel across the
+    // whole mip chain.
+    if (any(isnan(envcolor)) || any(isinf(envcolor))) envcolor = vec3(0.0);
+    return max(envcolor, vec3(0.0));
 #else
     return vec3(0.5); // was vec3(0.0), match the non-LOD fallback
 #endif

shaders/tonemapping.glsl

@@ -46,6 +46,17 @@ vec4 tonemap(vec4 x)
 	// with pureWhite=1.0 it collapses to identity (L*(1+L)/(1+L) = L) and
 	// just clips HDR>1.0 at the framebuffer -> washed-out / burnt look.
 	// ACES gives a smooth highlight shoulder + slight toe contrast.
-	return FBOUT(vec4(ACESFilm(x.rgb), x.a));
+
+	// Last-line-of-defense sanitize. ACESFilm has the form
+	//   (x*(a*x+b)) / (x*(c*x+d)+e)
+	// which maps NaN -> NaN and +Inf -> NaN (Inf/Inf). Either turns the
+	// pixel black after framebuffer clamp. A negative HDR input feeds a
+	// negative numerator/denominator and can produce non-physical output
+	// that also looks like a black flash. Clamp to a sensible range
+	// before the curve so a single bad upstream pixel can't escape.
+	vec3 hdr = x.rgb;
+	hdr = mix(hdr, vec3(0.0), vec3(any(isnan(hdr)) || any(isinf(hdr))));
+	hdr = max(hdr, vec3(0.0));
+	return FBOUT(vec4(ACESFilm(hdr), x.a));
 	//return FBOUT(vec4(reinhard(x.rgb), x.a));
 }