Editing Texture mapping (section)

====Forward texture mapping====
Forward texture mapping maps each texel of the texture to a pixel on the screen. After transforming a rectangular primitive to a place on the screen, a forward texture mapping renderer iterates through each texel on the texture, splatting each one onto a pixel of the [[frame buffer]].

This was used by some hardware, such as the [[3DO Interactive Multiplayer|3DO]], the [[Sega Saturn]] and the [[NV1]].

The primary advantage is that the texture will be accessed in a simple linear order, allowing very efficient caching of the texture data. However, this benefit is also its disadvantage: as a primitive gets smaller on screen, it still has to iterate over every texel in the texture, causing many pixels to be overdrawn redundantly.

This method is also well suited for rendering quad primitives rather than reducing them to triangles, which provided an advantage when perspective correct texturing was not available in hardware. This is because the affine distortion of a quad looks less incorrect than the same quad split into two triangles (see [[#Affine texture mapping|affine texture mapping]] above). The NV1 hardware also allowed a quadratic interpolation mode to provide an even better approximation of perspective correctness.

The existing hardware implementations did not provide effective [[UV coordinates|UV coordinate mapping]], which became an important technique for 3D modelling and assisted in [[Clipping (computer graphics)|clipping]] the texture correctly when the primitive goes over the edge of the screen. These shortcomings could have been addressed with further development, but GPU design has since mostly moved toward inverse mapping.

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