better structure

config/cava/shaders/pass_through.vert

@@ -0,0 +1,14 @@
+#version 330
+
+
+// Input vertex data, different for all executions of this shader.
+layout(location = 0) in vec3 vertexPosition_modelspace;
+
+// Output data ; will be interpolated for each fragment.
+out vec2 fragCoord;
+
+void main()
+{
+    gl_Position =  vec4(vertexPosition_modelspace,1);
+    fragCoord  = (vertexPosition_modelspace.xy+vec2(1,1))/2.0;
+}