subroutines test

shaders/frag4.glsl

@@ -1,11 +1,12 @@
 // FX B
-// ---------
-// IN: 4 / 6
-// OUT: 6
+// -------------
+// IN: 4 (SRC B)
+// IN: 6 (FX B)
+// OUT: 6 (A+B)
 
 in vec2 vUV;
 layout(location = 6) out vec3 fragColor;
 
 void main() {
-    fragColor = texture(frame4, vUV).xyz;
+    fragColor = fx_stage(vUV, frame4, frame6);
 }