SuperTuxKart 1.5 upstream source (from official release tarball)

data/shaders/sp_transparent.frag

@@ -0,0 +1,36 @@
+uniform int fog_enabled;
+uniform float custom_alpha;
+
+in vec2 uv;
+in vec4 color;
+out vec4 o_diffuse_color;
+
+#stk_include "utils/sp_texture_sampling.frag"
+
+void main()
+{
+    vec4 diffusecolor = sampleTextureLayer0(uv);
+    vec4 finalcolor = vec4(0.);
+    if (fog_enabled == 0)
+    {
+        finalcolor = diffusecolor;
+        finalcolor.xyz *= color.xyz;
+        finalcolor.a *= color.a;
+    }
+    else
+    {
+        diffusecolor.xyz *= color.xyz;
+        diffusecolor.a *= color.a;
+        vec3 tmp = vec3(gl_FragCoord.xy / u_screen, gl_FragCoord.z);
+        tmp = 2. * tmp - 1.;
+        vec4 xpos = vec4(tmp, 1.0);
+        xpos = u_inverse_projection_matrix * xpos;
+        xpos.xyz /= xpos.w;
+        float dist = length(xpos.xyz);
+        float fog = smoothstep(u_fog_data.x, u_fog_data.y, dist);
+        fog = min(fog, u_fog_data.z);
+        finalcolor = u_fog_color * fog + diffusecolor * (1. - fog);
+    }
+    o_diffuse_color = vec4(finalcolor.rgb * (finalcolor.a * (1.0 - custom_alpha)),
+        finalcolor.a * (1.0 - custom_alpha));
+}