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Danny McGee
55 lines
1.9 KiB
Markdown
55 lines
1.9 KiB
Markdown
# Generating Skybox and Image-Based Lighting Assets
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HDRI images like those available at [Poly Haven](https://polyhaven.com/hdris/skies)
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or [HDRI Haven](https://hdri-haven.com) must be preprocessed before they can be
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used for skyboxes and image-based lighting in Bevy Engine. Ultimately, three
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files are required:
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* An `*.hdr` cubemap texture for the skybox
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* A `*.ktx2` prefiltered diffuse irradiance cubemap for IBL
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* A `*.ktx2` prefiltered specular cubemap for IBL
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The HDR cubemap texture currently must be generated using Blender. A helper
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asset with instructions is available [here](https://drive.google.com/file/d/1UG_w9a6XfRmZtcfsSwFTDWPF7KnRa56I/view?usp=sharing)
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for Blender 3.6.
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The prefiltered IBL cubemaps are generated with two CLI tools:
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1. [glTF IBL Sampler](https://github.com/KhronosGroup/glTF-IBL-Sampler)
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* Git clone with `--recursive` and build using CMake
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* Diffuse:
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```sh
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./path/to/build-output/cli \
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-inputPath <input>.hdr \
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-outCubeMap <output>_diffuse.ktx2 \
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-distribution Lambertian \
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-cubeMapResolution 32
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```
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* Specular:
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```sh
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./path/to/build-output/cli \
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-inputPath <input>.hdr \
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-outCubeMap <output>_specular.ktx2 \
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-distribution GGX \
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-cubeMapResolution 512
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```
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2. [bevy_mod_environment_map_tools](https://github.com/DGriffin91/bevy_mod_environment_map_tools)
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* You can run this directly with `cargo` on the files generated by the
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previous step:
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```sh
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cargo run --release -- \
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--inputs <input>_diffuse.ktx2,<input>_specular.ktx2 \
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--outputs <output>_diffuse.zstd.ktx2,<output>_specular.zstd.ktx2
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```
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The Bevy app expects the filenames to exactly match the patterns given in the
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examples above:
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* `{name}.hdr`
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* `{name}_diffuse.zstd.ktx2`
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* `{name}_specular.zstd.ktx2`
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Once the files are in place, the application's `skybox` module can load all of
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the associated files for a skybox by passing its `name` to a helper function.
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