Add wall shadow shaders

shader/wallShadow.geom

@@ -0,0 +1,26 @@
+#version 430 core
+layout (points) in;
+layout (triangle_strip, max_vertices = 4) out;
+
+in vec4 vBackPoss[];
+uniform vec2 lightPos;
+
+void main()
+{
+  vec2 posa = gl_in[0].gl_Position.xy;
+  vec2 posb = gl_in[0].gl_Position.zw;
+  vec2 v = normalize( posb - posa);
+  vec2 off = vec2( -(v.y *0.2) 
+                 , v.x *0.2 );
+
+  gl_Position = vec4 (posa, 0 , 1);
+  EmitVertex();
+  gl_Position = vec4 (posb, 0 , 1);
+  EmitVertex();
+  gl_Position = vec4 (posa + off, 0 , 1);
+  EmitVertex();
+  gl_Position = vec4 (posb + off, 0 , 1);
+  EmitVertex();
+
+  EndPrimitive();
+}