Gloom: Refraction offset depends on volumetric distance

The offset should be smaller near the surface.

doomsday/tests/test_gloom/net.dengine.gloom.pack/shaders/surface_transparent.fsh

@@ -44,13 +44,13 @@ void main(void) {
 
     mat3 tsToViewRotate = uWorldToViewRotate * Gloom_TangentMatrix(ts);
     vec3 vsNormal = tsToViewRotate * normal;
-    
+
     vec4 diffuse   = Gloom_FetchTexture(matIndex, Texture_Diffuse, texCoord);
     float density  = diffuse.a;
     vec3 emissive  = Gloom_FetchTexture(matIndex, Texture_Emissive, texCoord).rgb;
     vec4 specGloss = Gloom_FetchTexture(matIndex, Texture_SpecularGloss, texCoord);
     vec3 vsViewDir = -normalize(vVSPos.xyz);
-            
+
     vec3 vsPos = vVSPos.xyz / vVSPos.w;
 
     // Write a displaced depth.  // TODO: Add a routine for doing this.
@@ -63,43 +63,46 @@ void main(void) {
     else {
         gl_FragDepth = gl_FragCoord.z;
     }
-    
+
     float viewDistance = length(vsPos);
-
+    float directVolDist = distance(vsPos, GBuffer_ViewSpacePos(vUV).xyz);
+
     // Refraction. This is calculated in view space so the offset will be view-dependent.
     vec4  refractedColor;
     float reflectRatio;
     vec3  refracted = refract(vsViewDir, vsNormal, 1.05);
     if (refracted != vec3(0.0)) {
         reflectRatio = max(0.0, dot(refracted, vsViewDir));
-        float refrFactor = 0.05 / max(1.0, viewDistance * 0.5);
-            vec2 fragPos = (gl_FragCoord.xy + refracted.xy * uViewportSize.y * refrFactor) / uViewportSize;
-            refractedColor = texture(uRefractedFrame, fragPos) * (1.0 - reflectRatio);       
-            backPos = GBuffer_ViewSpacePos(fragPos).xyz;
-
-            // How far does light travel through the volume?
-            // if (backPos.z < vsPos.z) {
-                float volumetric = pow(density, 2.0) * 5.0 * log(distance(backPos, vsPos) + 1.0);
-                if (density > 0.0) {
-                    refractedColor = mix(refractedColor, diffuse, 
-                        min(volumetric /* * density + pow(density, 2.0)*/, 1.0));
-                }
-            // }
-            // else {
-            //     refractedColor = vec4(0.0);
-            // }
+        float refrFactor = 0.05 / max(1.0, viewDistance * 0.5) *
+            min(directVolDist * 4.0, 1.0);
+        vec2 fragPos = (gl_FragCoord.xy + refracted.xy * uViewportSize.y * refrFactor) / uViewportSize;
+        refractedColor = texture(uRefractedFrame, fragPos) * (1.0 - reflectRatio);
+        backPos = GBuffer_ViewSpacePos(fragPos).xyz;
+
+        // How far does light travel through the volume?
+        // if (backPos.z < vsPos.z) {
+        float volDist = distance(backPos, vsPos);
+        float volumetric = pow(density, 2.0) * 5.0 * log(volDist + 1.0);
+        if (density > 0.0) {
+            refractedColor = mix(refractedColor, diffuse,
+                min(volumetric /* * density + pow(density, 2.0)*/, 1.0));
+        }
+        // }
+        // else {
+        //     refractedColor = vec4(0.0);
+        // }
     }
     else {
         refractedColor = vec4(0.0);
         reflectRatio = 1.0;
     }
-    
+
     // Now we can apply lighting to the surface.
     SurfacePoint sp = SurfacePoint(vsPos, vsNormal, diffuse.rgb * diffuse.a, specGloss);
 
     out_FragColor = vec4(emissive, 0.0) + refractedColor;
-    out_FragColor.rgb += 
-        Gloom_DirectionalLighting(sp) + 
+    out_FragColor.rgb +=
+        Gloom_DirectionalLighting(sp) +
         Gloom_OmniLighting(sp) +
         reflectRatio * Gloom_CubeReflection(uEnvMap, sp);
 }