A HDRE is a binary file containing the information of a cubemap environment and some of the computed mipmapped versions needed in Photorealistic Rendering (PBR) to simulate different materials (Prefiltering steps). It also contains other information as the values for the spherical harmonics (since v1.5) or the maximum luminance.
Since v2.0 there is an available version for C++ applications.
PBR Irradiance and reflection probes rendered using HDRE files
To create images you must use the HDRETool or download them from the HDRERepository.
Contains all the HDRE properties. Default size: 256 bytes [v2.0].
| Property | Size |
|---|---|
| Header signature ("HDRE") | 4 bytes |
| Version | 4 bytes |
| Width | 2 bytes |
| Height | 2 bytes |
| Max file size | 4 bytes |
| Number of channels | 2 bytes |
| Bits per channel | 2 bytes |
| Header size | 2 bytes |
| Encoding (LE) | 2 bytes |
| Maximum luminance | 4 bytes |
| Data type (UInt, Float..) | 2 bytes |
| SH (9 coef) [v2.0] |
The maximum size of a texture stored in HDRE is 256x256 pixels per face. Each prefiltered level is stored using half the size of the previous one so it is possible to store them in the mipmaps of the original image. In the case of a 256 sized HDRE, the mipmap levels would be:
- Original image: 256x256
- Mip1: 128x128
- Mip2: 64x64
- Mip3: 32x32
- Mip4: 16x16
- Mip5: 8x8
Note: Faces are stored individually, removing empty spaces when using cubemaps.
