Clouds are affected by (underlying) lightmap

shader/lighting/capTest.geom

@@ -0,0 +1,57 @@
+#version 430 core
+// an attempt to test whether a geometry surface occludes the camera from a
+// light source
+layout (triangles) in;
+layout (triangle_strip, max_vertices = 4) out;
+layout (std140, binding = 0) uniform TheMat { mat4 theMat; } ;
+uniform vec3 lightPos;
+uniform vec2 camPos;
+void main()
+{
+    vec3 p0 = gl_in[0].gl_Position.xyz ;
+    vec3 p1 = gl_in[1].gl_Position.xyz ;
+    vec3 p2 = gl_in[2].gl_Position.xyz ;
+    
+    // first determine intersection point (if any)
+
+    vec3 u = p1 - p0 ;
+    vec3 v = p2 - p0 ;
+    vec3 n = cross (u,v) ;
+    vec3 dir = vec3 (camPos, 100) - lightPos ;
+    vec3 w0 = p0 - lightPos ;
+    float a = dot(n, w0) ;
+    float b = dot(n,dir) ;
+    if (abs(b) < 0.00001) {}
+    else {
+        float r = a / b ;   
+        if (r < 0.0) {}
+        else {
+            vec3 ip = lightPos + r * dir ;
+            float uu, uv, vv, wu, wv, D;
+            uu = dot(u,u);
+            uv = dot(u,v);
+            vv = dot(v,v);
+            vec3 w = ip - p0;
+            wu = dot (w,u);
+            wv = dot (w,v);
+            D = uv * uv - uu * vv;
+            //get and test parametric coords
+            float s, t;
+            s = (uv * wv - vv * wu) / D;
+            if (s < 0.0 || s > 1.0) {}
+            else
+            {
+                t = (uv * wu - uu * wv) / D;
+                if (t < 0.0 || (s + t) > 1.0) {}
+                else
+                {
+                    gl_Position = vec4(-1,-1,50,1); EmitVertex();
+                    gl_Position = vec4(-1, 1,50,1); EmitVertex();
+                    gl_Position = vec4( 1,-1,50,1); EmitVertex();
+                    gl_Position = vec4( 1, 1,50,1); EmitVertex();
+                    EndPrimitive();
+                }
+            }
+        }
+    }
+}