Debug quad shader

Fixes #424

data/shaders/shadowmapping/quad.vert

@@ -1,27 +1,14 @@
 #version 450
 
-#extension GL_ARB_separate_shader_objects : enable
-#extension GL_ARB_shading_language_420pack : enable
-
-layout (location = 0) in vec3 inPos;
-layout (location = 1) in vec2 inUV;
-
-layout (binding = 0) uniform UBO 
-{
-	mat4 projection;
-	mat4 model;
-} ubo;
-
 layout (location = 0) out vec2 outUV;
 
 out gl_PerVertex 
 {
-    vec4 gl_Position;   
+	vec4 gl_Position;   
 };
 
-
 void main() 
 {
-	outUV = inUV;
+	outUV = vec2((gl_VertexIndex << 1) & 2, gl_VertexIndex & 2);
-	gl_Position = ubo.projection * ubo.model * vec4(inPos.xyz, 1.0);
+	gl_Position = vec4(outUV, 0.0f, 1.0f);
 }