Add line shadow shader

shader/lighting/lineShadow.geom

@@ -0,0 +1,19 @@
+#version 430 core
+layout (lines) in;
+layout (triangle_strip, max_vertices = 4) out;
+layout (std140, binding = 0) uniform TheMat { mat4 theMat; } ;
+uniform vec3 lightPos;
+vec4 shift (vec4 p) { return (vec4 (p.xyz + (2000*(p.xyz-lightPos)), 1));}
+vec4 f (vec4 p) {return (theMat * p);}
+void main()
+{
+    vec4 p0 = gl_in[0].gl_Position;
+    gl_Position = f(p0); EmitVertex();
+    vec4 p1 = gl_in[1].gl_Position;
+    gl_Position = f(p1); EmitVertex();
+    vec4 p2 = shift(p0);
+    gl_Position = f(p2); EmitVertex();
+    vec4 p3 = shift(p1);
+    gl_Position = f(p3); EmitVertex();
+    EndPrimitive();
+}