Gource is cool

gource/data/shaders/shadow.frag

@@ -0,0 +1,9 @@
+uniform sampler2D tex;
+uniform float shadow_strength;
+
+void main(void)
+{
+    vec4 colour = texture2D(tex,gl_TexCoord[0].st);
+
+    gl_FragColor = vec4(0.0, 0.0, 0.0, gl_Color.w * colour.w * shadow_strength);
+}