openGL: Add preliminary multi-texturing code.

3-mid/opengl/assets/shader/lit_textured_x2.vert

@@ -0,0 +1,29 @@
+#version 140
+
+uniform mat4   mvp_Transform;
+uniform vec3   Scale;
+
+in vec3        Site;
+in vec3        Normal;
+in vec2        Coords;
+in float       Shine;
+
+out vec3       frag_Site;
+out vec3       frag_Normal;
+out vec2       frag_Coords;
+out float      frag_Shine;
+
+
+void main()
+{
+    // Pass some variables to the fragment shader.
+    //
+    frag_Site   = Site;
+    frag_Normal = Normal;
+    frag_Coords = Coords;
+    frag_Shine  = Shine;
+    
+    // Apply all matrix transformations to 'Site'.
+    //
+    gl_Position = mvp_Transform * vec4 (Site * Scale, 1);
+}