Shader refactor

shaders/flat.frag

@@ -16,22 +16,30 @@ struct Material {
   bool usesTex;
   float alphaScissor;
   bool unshaded;
+  bool cullBack;
 };
 
 uniform Material material;
 
 void main() {
   FragColor = vec4(0.0);
+  
   if (material.usesColor) {
     FragColor += vec4(material.color, 1.0);
   }
+  
   if (material.usesTex) {
     FragColor += texture(material.tex, UV);
   }
+  
   if (FragColor.w < material.alphaScissor) {
     discard;
   }
 
+  if (material.cullBack && !gl_FrontFacing) {
+    discard;
+  }
+
   if (!material.unshaded) {
     FragColor *= vec4(AMBIENT + DIFFUSE + SPECULAR, 1.0);
   }

shaders/screen.frag

@@ -4,15 +4,8 @@ in vec2 UV;
 
 out vec4 FragColor;
 
-struct Material {
-  vec3 color;
-  bool usesColor;
-  sampler2D tex;
-  bool usesTex;
-};
-
-uniform Material material;
+uniform sampler2D tex;
 
 void main() {
-  FragColor = texture(material.tex, UV);
+  FragColor = texture(tex, UV);
 }