Cube mapping
However, hardware limitations on the ability to access six texture images simultaneously made it infeasible to implement cube mapping without further technological developments.
Nvidia touted cube mapping in hardware as “a breakthrough image quality feature of GeForce 256 that ... will allow developers to create accurate, real-time reflections.
Although these image flaws can be reduced using certain tricks and techniques like “pre-stretching”, this just adds another layer of complexity to sphere mapping.
Conversely, cube mapping requires only a single render pass, and due to its simple nature, is very easy for developers to comprehend and generate.
[citation needed] Computer-aided design (CAD) programs use specular highlights as visual cues to convey a sense of surface curvature when rendering 3D objects.
This in turn results in highlights with brightness proportionate to the distance from mesh vertices, ultimately compromising the visual cues that indicate curvature.
Cube maps provide a fairly straightforward and efficient solution to rendering stable specular highlights.
Multiple specular highlights can be encoded into a cube map texture, which can then be accessed by interpolating across the surface's reflection vector to supply coordinates.
Relative to computing lighting at individual vertices, this method provides cleaner results that more accurately represent curvature.
Another advantage to this method is that it scales well, as additional specular highlights can be encoded into the texture at no increase in the cost of rendering.
However, a cube map texture can be consistently updated to represent a dynamically changing environment (for example, trees swaying in the wind).
A simple yet costly way to generate dynamic reflections, involves building the cube maps at runtime for every frame.
An algorithm for global illumination computation at interactive rates using a cube-map data structure, was presented at ICCVG 2002.
This enables a game developer to achieve realistic lighting without having to complicate the scene geometry or resort to expensive real-time shadow volume computations.
