Cubemap arrays required for full multi-probe based IBL

[scratchyrice]

Current full blown multi-probe based IBL is not doable due to the lack of cube map arrays. Cube map arrays are required to bind the light probe diffuse and specular cube maps to the IBL shader.

[paroj]

ogre-next usages for reference: https://github.com/search?q=repo%3AOGRECave%2Fogre-next+TypeCubeArray&type=code&p=1