Fog in ubershader

docs/3ds/lighting.md

@@ -56,7 +56,7 @@ lut_id is one of these values
 6 	RR 
 
 lut_index on the other hand represents the actual index of the LUT in the texture
-u_tex_lighting_lut has 24 LUTs and they are used like so:
+u_tex_luts has 24 LUTs for lighting and they are used like so:
 0 		D0
 1 		D1
 2 		is missing because SP uses LUTs 8-15

include/PICA/gpu.hpp

@@ -92,6 +92,9 @@ class GPU {
 	// Set to false by the renderer when the lighting_lut is uploaded ot the GPU
 	bool lightingLUTDirty = false;
 
+	std::array<uint32_t, 128> fogLUT;
+	bool fogLUTDirty = false;
+
 	GPU(Memory& mem, EmulatorConfig& config);
 	void display() { renderer->display(); }
 	void screenshot(const std::string& name) { renderer->screenshot(name); }

include/PICA/regs.hpp

@@ -51,6 +51,18 @@ namespace PICA {
 			#undef defineTexEnv
 			// clang-format on
 
+			// Fog registers
+			FogColor = 0xE1,
+			FogLUTIndex = 0xE6,
+			FogLUTData0 = 0xE8,
+			FogLUTData1 = 0xE9,
+			FogLUTData2 = 0xEA,
+			FogLUTData3 = 0xEB,
+			FogLUTData4 = 0xEC,
+			FogLUTData5 = 0xED,
+			FogLUTData6 = 0xEE,
+			FogLUTData7 = 0xEF,
+
 			// Framebuffer registers
 			ColourOperation = 0x100,
 			BlendFunc = 0x101,

include/renderer_gl/renderer_gl.hpp

@@ -63,7 +63,7 @@ class RendererGL final : public Renderer {
 	OpenGL::VertexBuffer dummyVBO;
 
 	OpenGL::Texture screenTexture;
-	OpenGL::Texture lightLUTTexture;
+	OpenGL::Texture LUTTexture;
 	OpenGL::Framebuffer screenFramebuffer;
 	OpenGL::Texture blankTexture;
 	// The "default" vertex shader to use when using specialized shaders but not PICA vertex shader -> GLSL recompilation
@@ -90,6 +90,7 @@ class RendererGL final : public Renderer {
 	void setupUbershaderTexEnv();
 	void bindTexturesToSlots();
 	void updateLightingLUT();
+	void updateFogLUT();
 	void initGraphicsContextInternal();
 
   public:

src/core/PICA/gpu.cpp

@@ -74,6 +74,9 @@ void GPU::reset() {
 	lightingLUT.fill(0);
 	lightingLUTDirty = true;
 
+	fogLUT.fill(0);
+	fogLUTDirty = true;
+
 	totalAttribCount = 0;
 	fixedAttribMask = 0;
 	fixedAttribIndex = 0;

src/core/PICA/regs.cpp

@@ -135,6 +135,21 @@ void GPU::writeInternalReg(u32 index, u32 value, u32 mask) {
 			break;
 		}
 
+		case FogLUTData0:
+		case FogLUTData1:
+		case FogLUTData2:
+		case FogLUTData3:
+		case FogLUTData4:
+		case FogLUTData5:
+		case FogLUTData6:
+		case FogLUTData7: {
+			const uint32_t index = regs[FogLUTIndex] & 127;
+			fogLUT[index] = value;
+			fogLUTDirty = true;
+			regs[FogLUTIndex] = (index + 1) & 127;
+			break;
+		}
+
 		case LightingLUTData0:
 		case LightingLUTData1:
 		case LightingLUTData2:

src/core/PICA/shader_gen_glsl.cpp

@@ -130,7 +130,7 @@ std::string FragmentGenerator::generate(const FragmentConfig& config) {
 		uniform sampler2D u_tex0;
 		uniform sampler2D u_tex1;
 		uniform sampler2D u_tex2;
-		uniform sampler2D u_tex_lighting_lut;
+		uniform sampler2D u_tex_luts;
 	)";
 
 	ret += uniformDefinition;
@@ -144,7 +144,7 @@ std::string FragmentGenerator::generate(const FragmentConfig& config) {
 			}
 
 			float lutLookup(uint lut, int index) {
-				return texelFetch(u_tex_lighting_lut, ivec2(index, int(lut)), 0).r;
+				return texelFetch(u_tex_luts, ivec2(index, int(lut)), 0).r;
 			}
 
 			vec3 regToColor(uint reg) {

src/core/renderer_gl/renderer_gl.cpp

@@ -115,10 +115,11 @@ void RendererGL::initGraphicsContextInternal() {
 	const u32 screenTextureWidth = 400;       // Top screen is 400 pixels wide, bottom is 320
 	const u32 screenTextureHeight = 2 * 240;  // Both screens are 240 pixels tall
 
-	lightLUTTexture.create(256, Lights::LUT_Count, GL_R32F);
-	lightLUTTexture.bind();
-	lightLUTTexture.setMinFilter(OpenGL::Linear);
-	lightLUTTexture.setMagFilter(OpenGL::Linear);
+	// 24 rows for light, 1 for fog
+	LUTTexture.create(256, Lights::LUT_Count + 1, GL_RG32F);
+	LUTTexture.bind();
+	LUTTexture.setMinFilter(OpenGL::Linear);
+	LUTTexture.setMagFilter(OpenGL::Linear);
 
 	auto prevTexture = OpenGL::getTex2D();
 
@@ -353,22 +354,49 @@ void RendererGL::bindTexturesToSlots() {
 	}
 
 	glActiveTexture(GL_TEXTURE0 + 3);
-	lightLUTTexture.bind();
+	LUTTexture.bind();
 	glActiveTexture(GL_TEXTURE0);
 }
 
 void RendererGL::updateLightingLUT() {
 	gpu.lightingLUTDirty = false;
-	std::array<float, GPU::LightingLutSize> lightingLut;
+	std::array<float, GPU::LightingLutSize * 2> lightingLut;
 
-	for (int i = 0; i < gpu.lightingLUT.size(); i++) {
-		uint64_t value = gpu.lightingLUT[i] & 0xFFF;
+	for (int i = 0; i < lightingLut.size(); i += 2) {
+		uint64_t value = gpu.lightingLUT[i >> 1] & 0xFFF;
 		lightingLut[i] = (float)(value << 4) / 65535.0f;
 	}
 
 	glActiveTexture(GL_TEXTURE0 + 3);
-	lightLUTTexture.bind();
-	glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 256, Lights::LUT_Count, GL_RED, GL_FLOAT, lightingLut.data());
+	LUTTexture.bind();
+	glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 256, Lights::LUT_Count, GL_RG, GL_FLOAT, lightingLut.data());
+	glActiveTexture(GL_TEXTURE0);
+}
+
+void RendererGL::updateFogLUT() {
+	gpu.fogLUTDirty = false;
+
+	// Fog LUT elements are of this type:
+	// 0-12     fixed1.1.11, Difference from next element
+	// 13-23    fixed0.0.11, Value
+	// We will store them as a 128x1 RG texture with R being the value and G being the difference
+	std::array<float, 128 * 2> fogLut;
+
+	for (int i = 0; i < fogLut.size(); i += 2) {
+		const uint32_t value = gpu.fogLUT[i >> 1];
+		int32_t diff = value & 0x1fff;
+		diff = (diff << 19) >> 19;  // Sign extend the 13-bit value to 32 bits
+		const float fogDifference = float(diff) / 2048.0f;
+		const float fogValue = float((value >> 13) & 0x7ff) / 2048.0f;
+
+		fogLut[i] = fogValue;
+		fogLut[i + 1] = fogDifference;
+	}
+
+	glActiveTexture(GL_TEXTURE0 + 3);
+	LUTTexture.bind();
+	// The fog LUT exists at the end of the lighting LUT
+	glTexSubImage2D(GL_TEXTURE_2D, 0, 0, Lights::LUT_Count, 128, 1, GL_RG, GL_FLOAT, fogLut.data());
 	glActiveTexture(GL_TEXTURE0);
 }
 
@@ -453,6 +481,10 @@ void RendererGL::drawVertices(PICA::PrimType primType, std::span<const Vertex> v
 
 	bindTexturesToSlots();
 
+	if (gpu.fogLUTDirty) {
+		updateFogLUT();
+	}
+
 	if (gpu.lightingLUTDirty) {
 		updateLightingLUT();
 	}
@@ -811,7 +843,7 @@ OpenGL::Program& RendererGL::getSpecializedShader() {
 		glUniform1i(OpenGL::uniformLocation(program, "u_tex0"), 0);
 		glUniform1i(OpenGL::uniformLocation(program, "u_tex1"), 1);
 		glUniform1i(OpenGL::uniformLocation(program, "u_tex2"), 2);
-		glUniform1i(OpenGL::uniformLocation(program, "u_tex_lighting_lut"), 3);
+		glUniform1i(OpenGL::uniformLocation(program, "u_tex_luts"), 3);
 
 		// Allocate memory for the program UBO
 		glGenBuffers(1, &programEntry.uboBinding);
@@ -994,9 +1026,9 @@ void RendererGL::initUbershader(OpenGL::Program& program) {
 	ubershaderData.depthmapEnableLoc = OpenGL::uniformLocation(program, "u_depthmapEnable");
 	ubershaderData.picaRegLoc = OpenGL::uniformLocation(program, "u_picaRegs");
 
-	// Init sampler objects. Texture 0 goes in texture unit 0, texture 1 in TU 1, texture 2 in TU 2, and the light maps go in TU 3
+	// Init sampler objects. Texture 0 goes in texture unit 0, texture 1 in TU 1, texture 2 in TU 2, light maps go in TU 3, and the fog map goes in TU 4
 	glUniform1i(OpenGL::uniformLocation(program, "u_tex0"), 0);
 	glUniform1i(OpenGL::uniformLocation(program, "u_tex1"), 1);
 	glUniform1i(OpenGL::uniformLocation(program, "u_tex2"), 2);
-	glUniform1i(OpenGL::uniformLocation(program, "u_tex_lighting_lut"), 3);
+	glUniform1i(OpenGL::uniformLocation(program, "u_tex_luts"), 3);
 }

src/host_shaders/opengl_fragment_shader.frag

@@ -25,7 +25,7 @@ uniform bool u_depthmapEnable;
 uniform sampler2D u_tex0;
 uniform sampler2D u_tex1;
 uniform sampler2D u_tex2;
-uniform sampler2D u_tex_lighting_lut;
+uniform sampler2D u_tex_luts;
 
 uniform uint u_picaRegs[0x200 - 0x48];
 
@@ -152,6 +152,8 @@ vec4 tevCalculateCombiner(int tev_id) {
 #define RG_LUT 5u
 #define RR_LUT 6u
 
+#define FOG_INDEX 24
+
 uint GPUREG_LIGHTi_CONFIG;
 uint GPUREG_LIGHTING_CONFIG1;
 uint GPUREG_LIGHTING_LUTINPUT_SELECT;
@@ -161,7 +163,7 @@ bool error_unimpl = false;
 vec4 unimpl_color = vec4(1.0, 0.0, 1.0, 1.0);
 
 float lutLookup(uint lut, int index) {
-	return texelFetch(u_tex_lighting_lut, ivec2(index, int(lut)), 0).r;
+	return texelFetch(u_tex_luts, ivec2(index, int(lut)), 0).r;
 }
 
 vec3 regToColor(uint reg) {
@@ -494,7 +496,7 @@ void main() {
 	if (tevUnimplementedSourceFlag) {
 		// fragColour = vec4(1.0, 0.0, 1.0, 1.0);
 	}
-	// fragColour.rg = texture(u_tex_lighting_lut,vec2(gl_FragCoord.x/200.,float(int(gl_FragCoord.y/2)%24))).rr;
+	// fragColour.rg = texture(u_tex_luts,vec2(gl_FragCoord.x/200.,float(int(gl_FragCoord.y/2)%24))).rr;
 
 	// Get original depth value by converting from [near, far] = [0, 1] to [-1, 1]
 	// We do this by converting to [0, 2] first and subtracting 1 to go to [-1, 1]
@@ -507,6 +509,28 @@ void main() {
 	// Write final fragment depth
 	gl_FragDepth = depth;
 
+	bool enable_fog = (textureEnvUpdateBuffer & 7u) == 5u;
+
+	if (enable_fog) {
+		bool flip_depth = (textureEnvUpdateBuffer & (1u << 16)) != 0u;
+		float fog_index = flip_depth ? 1.0 - depth : depth;
+		fog_index *= 128.0;
+		float clamped_index = clamp(floor(fog_index), 0.0, 127.0);
+		float delta = fog_index - clamped_index;
+		vec2 value = texelFetch(u_tex_luts, ivec2(int(clamped_index), FOG_INDEX), 0).rg;
+		float fog_factor = clamp(value.r + value.g * delta, 0.0, 1.0);
+
+		uint GPUREG_FOG_COLOR = readPicaReg(0x00E1u);
+
+		// Annoyingly color is not encoded in the same way as light color
+		float r = (GPUREG_FOG_COLOR & 0xFFu) / 255.0;
+		float g = ((GPUREG_FOG_COLOR >> 8) & 0xFFu) / 255.0;
+		float b = ((GPUREG_FOG_COLOR >> 16) & 0xFFu) / 255.0;
+		vec3 fog_color = vec3(r, g, b);
+
+		fragColour.rgb = mix(fog_color, fragColour.rgb, fog_factor);
+	}
+
 	// Perform alpha test
 	uint alphaControl = readPicaReg(0x104u);
 	if ((alphaControl & 1u) != 0u) {  // Check if alpha test is on