Diffusely convolved cube map
Contents
Introduction
A diffusely convolved cube map is simply a blurred-down version of a regular cube map. When a shader adds the cube map to the model's diffuse map the result is similar to global-illumination, except it is extremely efficient performance-wise.
AMD Cubemapgen
- Cubemapgen is open-sourced utility for filtering down cube maps.
- Sébastien Lagarde made a modified version for physically based rendering
Cubemapgen Cube Faces
| Cubemapgen | 3ds Max | Maya | CryENGINE 3 | Unity |
| +X | _RT | Left -X | ||
| -X | _LF | Right +X | ||
| +Y | _UP | Top +Y | ||
| -Y | _DN | Bottom -Y | ||
| +Z | _BK | Front (+Z) | ||
| -Z | _FR | Back (-Z) |
| Cubemapgen | 3ds Max | Maya | CryENGINE 3 | Unity |
| c00 | Left -X (180°) | |||
| c01 | Right +X (180°) | |||
| c02 | Top +Y | |||
| c03 | Bottom -Y | |||
| c04 | Back -Z (180°) | |||
| c05 | Front +Z (180°) |
Cubemapgen Custom Meshes
You can load your own geometry in Cubemapgen using the Load Object button, really helps to see what settings are working well.
You can also load a bitmap for the model using the Load Basemap button. There's a bug right now that causes your Basemap to be mirrored vertically... to fix it pre-flip the bitmap yourself before loading it in Cubemapgen. An Ambient Occlusion Map map makes a great Basemap, or you can use your DiffuseMap.
Editing Cubemaps in Photoshop
If your cube map is in DDS cube format, you'll need the NVIDIA DDS plugin to load and save in Photoshop.
Unfortunately NVIDIA introduced some bugs when they updated the plugin, so now DDS cubes don't load mips properly. If you need to load cube maps with mips, here's an old version that does it right.
Links
- Cubemaps how-to and why by Zeller Samuel - A great introduction to Cubemaps.
- Cubemaps Tutorial by CGTextures.com - Tutorial using Nvidia's Photoshop plugin, AMD's CubeMapGen, and Photoshop to convert cubemaps to various layouts.
