smuud shadows

res/shaders/simple.frag

@@ -36,6 +36,9 @@ const float la = 0.1, lb = 0.01, lc = 0.001;
 
 const float ballRadius = 1.0;
 
+const float hardRadius = ballRadius;
+const float softRadius = ballRadius * 2.0;
+
 void main()
 {
     vec3 norm = normalize(normal);
@@ -45,12 +48,10 @@ void main()
     vec3 result = ambient;
 
     for (int i = 0; i < 3; i++) {
-        vec3 lightVector = lights[i].position - worldPositions;
-        vec3 lightDir = normalize(lightVector);
+        vec3 fragToLight = lights[i].position - worldPositions;
+        vec3 lightDir = normalize(fragToLight);
 
-        vec3 fragToBall = lights[i].position - ballPosition;
-
-        float d = length(lightVector);
+        float d = length(fragToLight);
         float attenuation = 1.0 / (la + d * lb + d * d * lc);
 
         float diff = max(dot(norm, lightDir), 0.0);
@@ -60,15 +61,23 @@ void main()
         float spec = pow(max(dot(norm, halfwayDir), 0.0), shininess);
         vec3 specular = specularStrength * spec * lights[i].color;
 
-        // the ball's light is put inside it, thus it would cast a shadow all over the scene.
-        // to counter-act this, we can simply exclude it. i should instead move the light.
-        // either way, it makes for a cool light (shadow?) show.
-        bool shadow = false;
-        if (i != 2) {
-            shadow = length(lightVector) > length(fragToBall) && dot(lightVector, fragToBall) < 0.0;
+        // shadow stuff
+        vec3 fragToBall = ballPosition - worldPositions;
+        float projDist = dot(fragToBall, lightDir);
+        float r = length(fragToBall - projDist * lightDir);
+        bool inShadowRegion = (projDist > 0.0) && (projDist < d);
+        float shadowFactor = 1.0;
+
+        // exclude ball light to avoid casting shadows everywhere
+        if (i != 2 && inShadowRegion) {
+            if (r <= hardRadius) {
+                shadowFactor = 0.0;
+            } else if (r < softRadius) {
+                shadowFactor = (r - hardRadius) / (softRadius - hardRadius);
+            }
         }
-        if (!shadow)
-            result += attenuation * (diffuse + specular) * objectColor;
+
+        result += shadowFactor * attenuation * (diffuse + specular) * objectColor;
     }
 
     color = vec4(result + dither(textureCoordinates), 1.0);