Coloring triangles with texture

opengl-test-two/trimap.vertexshader

@@ -1,11 +1,17 @@
 #version 330 core
 
+// Input vertex data, different for all executions of this shader.
 layout(location = 0) in vec3 vertexPosition_modelspace;
-layout(location = 1) in vec3 vertexColor;
-out vec3 fragmentColor;
+layout(location = 1) in vec2 vertexUV;
+
+// Output data ; will be interpolated for each fragment.
+out vec2 UV;
 
 void main(){
-    gl_Position.xyz = vertexPosition_modelspace;
-    gl_Position.w = 1.0;
-    fragmentColor = vertexColor;
+    // Output position of the vertex, in clip space : MVP * position
+    gl_Position = vec4(vertexPosition_modelspace,1);
+
+    // UV of the vertex. No special space for this one.
+    UV = vertexUV;
 }
+