Draw walls using perspective divide

shader/wall.geom

@@ -0,0 +1,31 @@
+#version 430 core
+layout (triangles) in;
+layout (triangle_strip, max_vertices = 4) out;
+
+in vec4 vParams[];
+
+uniform mat4 worldMat;
+
+vec2 lightPos = gl_in[0].gl_Position.xy;
+vec2 cornerA  = gl_in[1].gl_Position.xy;
+vec2 cornerB  = gl_in[2].gl_Position.xy;
+
+void main()
+{
+    gl_Position = worldMat * vec4(cornerA, 1, 1 );
+    EmitVertex();
+
+    gl_Position = worldMat * (vec4(cornerA, 10, 1 ) + (20,20,0,0));
+    gl_Position = vec4(1,0, 10, 1 );
+    EmitVertex();
+
+    gl_Position = worldMat * vec4(cornerB, 0, 1 );
+    gl_Position = vec4(0,1, -10, 1 );
+    EmitVertex();
+
+    gl_Position = worldMat * (vec4(cornerB, 0, 1 ) + (20,20,0,0));
+    gl_Position = vec4(1,1, 10, 1 );
+    EmitVertex();
+
+    EndPrimitive();
+}