In the RDP, the output from the Texture Engine is sent to the unit called the Texture Filter for filtering, after which it is passed to the Color Combiner. In the Texture Filter, filtering is performed in association with texel sampling to enlarge or reduce the texture.
Use the gDPSetTextureFilter command to select a sampling filter method:
| gDPSetTextureFilter(Gfx *gdl, u32 type) | ||
| type | The texture sampling mode | |
| G_TF_POINT | Point sampling | |
| (Enlarge single texels. Enlarged texels look like blocks) | ||
| G_TF_AVERAGE | Box average | |
| (Averaged, so smoother than point sampling) | ||
| G_TF_BILERP | Bilinear | |
| (Approximate bilinear interpolating 3 pixels) |
Usually you achieve the best results using bilinear interpolation, but this may not always be the case, depending on the orderliness of the texture and the scale at which the texture is being displayed. For actual games, you will also need to preprocess the texture data based on a thorough understanding of the topics covered in Chapters 12 and 13 of the Programming Manual.