Graded Backdrop Example
This example creates a graded backdrop, which is a texture mapped onto a geometry defining two triangles, which form a quad.
The geometry has a color for each vertex - the top two are white and the bottom two are light grey. This creates a colour gradient across the quad, which the texture is then multiplied with.
The backdrop is wrapped in a stationary node to prevent it from translating when we update the lookAt node. Likewise, it is wrapped in a billboard node, which prevents it from rotating when we update the lookAt.