Draw walls using perspective divide

shader/wall.frag

@@ -0,0 +1,9 @@
+#version 430 core
+in vec4 vParams;
+out vec4 fColor;
+
+void main()
+{
+  fColor = vec4 (0.9,0.5,0,1);
+  fColor = vParams;
+}

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();
+}

shader/wall.vert

@@ -0,0 +1,18 @@
+#version 430 core
+layout (location = 0) in vec3 pos;
+layout (location = 1) in vec4 params;
+
+out vec4 vParams;
+uniform mat4 worldMat;
+
+mat4 perspective =  
+    mat4 (1,0,0,0
+         ,0,1,0,0
+         ,0,0,1,1
+         ,0,0,0,1
+         ) ;
+void main()
+{
+  gl_Position = perspective * worldMat * vec4(pos.xyz, 1);
+  vParams = params;
+}