Port Saturn's Light dither shader for OGL

src/hardware/hw_main.c

@@ -914,10 +914,13 @@ consvar_t cv_glbatching = CVAR_INIT ("gr_batching", "On", 0, CV_OnOff, NULL);
 CV_PossibleValue_t glpalettedepth_cons_t[] = {{16, "16 bits"}, {24, "24 bits"}, {0, NULL}};
 void CV_glpaletterendering_OnChange(void);
 void CV_glpalettedepth_OnChange(void);
+void CV_gllightdithering_OnChange(void);
 
 consvar_t cv_glpaletterendering = CVAR_INIT ("gr_paletteshader", "Off", CV_CALL|CV_SAVE, CV_OnOff, CV_glpaletterendering_OnChange);
 consvar_t cv_glpalettedepth = CVAR_INIT ("gr_palettedepth", "16 bits", CV_SAVE|CV_CALL, glpalettedepth_cons_t, CV_glpalettedepth_OnChange);
 
+consvar_t cv_gllightdither = CVAR_INIT ("gr_lightdithering", "Off", CV_CALL|CV_SAVE, CV_OnOff, CV_gllightdithering_OnChange);
+
 // Isolates rendering to one of the top level portals.
 // (Stencil cutting of the portal is also disabled)
 // Use gr_printportals to find the number to use.
@@ -958,7 +961,15 @@ void CV_glpaletterendering_OnChange(void)
 	}
 }
 
-void CV_glpalettedepth_OnChange(void);
+void CV_gllightdithering_OnChange(void)
+{
+	ONLY_IF_GL_LOADED
+	if (gl_shadersavailable)
+	{
+		HWR_CompileShaders();
+	}
+}
+
 void CV_glpalettedepth_OnChange(void)
 {
 	ONLY_IF_GL_LOADED
@@ -1024,6 +1035,8 @@ void HWR_AddCommands(void)
 	CV_RegisterVar(&cv_glpaletterendering);
 	CV_RegisterVar(&cv_glpalettedepth);
 
+	CV_RegisterVar(&cv_gllightdither);
+
 	COM_AddCommand("gr_printportals", Command_Glprintportals_f);
 	CV_RegisterVar(&cv_gldebugportal);
 

src/hardware/hw_main.h

@@ -113,6 +113,7 @@ extern consvar_t cv_glsolvetjoin, cv_glpolytile, cv_glpolyshape;
 extern consvar_t cv_glbatching;
 extern consvar_t cv_glpaletterendering;
 extern consvar_t cv_glpalettedepth;
+extern consvar_t cv_gllightdither;
 extern consvar_t cv_gldebugportal;
 
 extern consvar_t cv_glskydebug;

src/hardware/hw_shaders.c

@@ -81,6 +81,7 @@ static shadertarget_t gl_shadertargets[NUMSHADERTARGETS];
 
 #define MODEL_LIGHTING_DEFINE "#define SRB2_MODEL_LIGHTING"
 #define PALETTE_RENDERING_DEFINE "#define SRB2_PALETTE_RENDERING"
+#define LIGHT_DITHERING_DEFINE "#define SRB2_LIGHT_DITHER"
 
 // Initialize shader variables and the backend's shader system. Load the base shaders.
 // Returns false if shaders cannot be used.
@@ -284,6 +285,9 @@ static char *HWR_PreprocessShader(char *original)
 	if (cv_glpaletterendering.value)
 		ADD_TO_LEN(PALETTE_RENDERING_DEFINE)
 
+	if (cv_gllightdither.value)
+		ADD_TO_LEN(LIGHT_DITHERING_DEFINE)
+
 #undef ADD_TO_LEN
 
 #define VERSION_PART "#version "
@@ -329,6 +333,9 @@ static char *HWR_PreprocessShader(char *original)
 	if (cv_glpaletterendering.value)
 		WRITE_DEFINE(PALETTE_RENDERING_DEFINE)
 
+	if (cv_gllightdither.value)
+		WRITE_DEFINE(LIGHT_DITHERING_DEFINE)
+
 #undef WRITE_DEFINE
 
 	// Write a #line directive, so compiler errors will report line numbers from the

src/hardware/hw_shaders.h

@@ -76,15 +76,53 @@
 //
 
 // Include GLSL_FLOOR_FUDGES or GLSL_WALL_FUDGES or define the fudges in shaders that use this macro.
+#define GLSL_DOOM_COLORMAP_DITHER \
+	"float baseValue = max(startmap * STARTMAP_FUDGE - scale * 0.5 * SCALE_FUDGE, cap);\n" \
+	"float endResolutionx = scr_resolution.x;\n" \
+	"float endResolutiony = scr_resolution.y;\n" \
+	"if (scr_resolution.x > 1280.0) {\n" \
+		"endResolutionx = scr_resolution.x * 0.5;\n" \
+	"}\n" \
+	"if (scr_resolution.y > 720.0) {\n" \
+		"endResolutiony = scr_resolution.y * 0.5;\n" \
+	"}\n" \
+	"float zFactor = clamp((z - 192.0) / (6144.0 - 192.0), 0.0, 1.0);\n" \
+	"int scaleFactor = int(mix(1.0, 8.0, zFactor));\n" \
+	"endResolutionx = endResolutionx * scaleFactor;\n" \
+	"endResolutiony = endResolutiony * scaleFactor;\n" \
+	"vec2 normalizedPosition = position * vec2(endResolutionx / scr_resolution.x, endResolutiony / scr_resolution.y);\n" \
+	"int x = int(mod(normalizedPosition.x, 4.0));\n" \
+	"int y = int(mod(normalizedPosition.y, 4.0));\n" \
+	"float bayerMatrix[4*4] = float[4*4](\n" \
+		"0.0, 8.0, 2.0, 10.0,\n" \
+		"12.0, 4.0, 14.0, 6.0,\n" \
+		"3.0, 11.0, 1.0, 9.0,\n" \
+		"15.0, 7.0, 13.0, 5.0\n" \
+	");\n" \
+	"#ifdef SRB2_PALETTE_RENDERING\n" \
+	"float threshold = (1.0 - pow(zFactor, 2.0)) * (bayerMatrix[y*4 + x] / 11.0);\n" \
+	"#else\n" \
+	"float threshold = (1.0 - pow(zFactor, 2.0)) * (bayerMatrix[y*4 + x] / 16.0);\n" \
+	"#endif\n" \
+	"return mix(baseValue + threshold - 0.5 / 16.0, baseValue, zFactor);\n"
+
+#define GLSL_DOOM_COLORMAP_NODITHER \
+	"return max(startmap * STARTMAP_FUDGE - scale * 0.5 * SCALE_FUDGE, cap);\n" \
+
 #define GLSL_DOOM_COLORMAP \
-	"float R_DoomColormap(float light, float z)\n" \
+	"uniform vec2 scr_resolution;\n" \
+	"float R_DoomColormap(float light, float z, vec2 position)\n" \
 	"{\n" \
 		"float lightnum = clamp(light / 17.0, 0.0, 15.0);\n" \
 		"float lightz = clamp(z / 16.0, 0.0, 127.0);\n" \
 		"float startmap = (15.0 - lightnum) * 4.0;\n" \
 		"float scale = 160.0 / (lightz + 1.0);\n" \
 		"float cap = (155.0 - light) * 0.26;\n" \
-		"return max(startmap * STARTMAP_FUDGE - scale * 0.5 * SCALE_FUDGE, cap);\n" \
+		"#ifdef SRB2_LIGHT_DITHER\n" \
+		GLSL_DOOM_COLORMAP_DITHER \
+		"#else\n" \
+		GLSL_DOOM_COLORMAP_NODITHER \
+		"#endif\n" \
 	"}\n"
 // lighting cap adjustment:
 // first num (155.0), increase to make it start to go dark sooner
@@ -94,7 +132,7 @@
 	"float R_DoomLightingEquation(float light)\n" \
 	"{\n" \
 		"float z = gl_FragCoord.z / gl_FragCoord.w;\n" \
-		"float colormap = floor(R_DoomColormap(light, z)) + 0.5;\n" \
+		"float colormap = floor(R_DoomColormap(light, z, gl_FragCoord.xy)) + 0.5;\n" \
 		"return clamp(colormap, 0.0, 31.0) / 32.0;\n" \
 	"}\n"
 
@@ -157,7 +195,7 @@
 #define GLSL_PALETTE_RENDERING \
 	"float tex_pal_idx = texture3D(palette_lookup_tex, vec3((texel * 63.0 + 0.5) / 64.0))[0] * 255.0;\n" \
 	"float z = gl_FragCoord.z / gl_FragCoord.w;\n" \
-	"float light_y = clamp(floor(R_DoomColormap(final_lighting, z)), 0.0, 31.0);\n" \
+	"float light_y = clamp(floor(R_DoomColormap(final_lighting, z, gl_FragCoord.xy)), 0.0, 31.0);\n" \
 	"vec2 lighttable_coord = vec2((tex_pal_idx + 0.5) / 256.0, (light_y + 0.5) / 32.0);\n" \
 	"vec4 final_color = texture2D(lighttable_tex, lighttable_coord);\n" \
 	"final_color.a = texel.a * poly_color.a;\n" \

src/hardware/r_opengl/r_opengl.c

@@ -654,6 +654,8 @@ typedef enum
 	// misc.
 	gluniform_leveltime,
 
+	gluniform_scr_resolution,
+
 	gluniform_max,
 } gluniform_t;
 
@@ -1935,6 +1937,8 @@ static void Shader_SetUniforms(FSurfaceInfo *Surface, GLRGBAFloat *poly, GLRGBAF
 
 		UNIFORM_1(shader->uniforms[gluniform_leveltime], shader_leveltime, pglUniform1f);
 
+		UNIFORM_2(shader->uniforms[gluniform_scr_resolution], (GLfloat)vid.width, (GLfloat)vid.height, pglUniform2f);
+
 		#undef UNIFORM_1
 		#undef UNIFORM_2
 		#undef UNIFORM_3
@@ -2050,24 +2054,26 @@ static boolean Shader_CompileProgram(gl_shader_t *shader, GLint i)
 	shader->uniforms[gluniform_brightmap] = GETUNI("brightmap");
 
 	// lighting
-	shader->uniforms[gluniform_poly_color] = GETUNI("poly_color");
+	shader->uniforms[gluniform_poly_color]            = GETUNI("poly_color");
-	shader->uniforms[gluniform_tint_color] = GETUNI("tint_color");
+	shader->uniforms[gluniform_tint_color]            = GETUNI("tint_color");
-	shader->uniforms[gluniform_fade_color] = GETUNI("fade_color");
+	shader->uniforms[gluniform_fade_color]            = GETUNI("fade_color");
-	shader->uniforms[gluniform_lighting] = GETUNI("lighting");
+	shader->uniforms[gluniform_lighting]              = GETUNI("lighting");
-	shader->uniforms[gluniform_fade_start] = GETUNI("fade_start");
+	shader->uniforms[gluniform_fade_start]            = GETUNI("fade_start");
-	shader->uniforms[gluniform_fade_end] = GETUNI("fade_end");
+	shader->uniforms[gluniform_fade_end]              = GETUNI("fade_end");
-	shader->uniforms[gluniform_newfade] = GETUNI("newfade");
+	shader->uniforms[gluniform_newfade]               = GETUNI("newfade");
-	shader->uniforms[gluniform_light_dir] = GETUNI("light_dir");
+	shader->uniforms[gluniform_light_dir]             = GETUNI("light_dir");
-	shader->uniforms[gluniform_light_contrast] = GETUNI("light_contrast");
+	shader->uniforms[gluniform_light_contrast]        = GETUNI("light_contrast");
-	shader->uniforms[gluniform_light_backlight] = GETUNI("light_backlight");
+	shader->uniforms[gluniform_light_backlight]       = GETUNI("light_backlight");
 
 	// palette rendering
-	shader->uniforms[gluniform_palette_tex] = GETUNI("palette_tex");
+	shader->uniforms[gluniform_palette_tex]           = GETUNI("palette_tex");
-	shader->uniforms[gluniform_palette_lookup_tex] = GETUNI("palette_lookup_tex");
+	shader->uniforms[gluniform_palette_lookup_tex]    = GETUNI("palette_lookup_tex");
-	shader->uniforms[gluniform_lighttable_tex] = GETUNI("lighttable_tex");
+	shader->uniforms[gluniform_lighttable_tex]        = GETUNI("lighttable_tex");
+
+	shader->uniforms[gluniform_scr_resolution]        = GETUNI("scr_resolution");
 
 	// misc. (custom shaders)
-	shader->uniforms[gluniform_leveltime] = GETUNI("leveltime");
+	shader->uniforms[gluniform_leveltime]             = GETUNI("leveltime");
 
 #undef GETUNI