https://github.com/elerac/btf-rendering
Custom plugin in Python for BTF (Bidirectional Texture Function) rendering with Mitsuba 2
https://github.com/elerac/btf-rendering
btf mitsuba python
Last synced: about 1 month ago
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Custom plugin in Python for BTF (Bidirectional Texture Function) rendering with Mitsuba 2
- Host: GitHub
- URL: https://github.com/elerac/btf-rendering
- Owner: elerac
- Created: 2020-09-11T11:51:16.000Z (over 4 years ago)
- Default Branch: master
- Last Pushed: 2023-12-08T01:48:14.000Z (over 1 year ago)
- Last Synced: 2025-03-24T13:21:25.912Z (about 2 months ago)
- Topics: btf, mitsuba, python
- Language: Python
- Homepage:
- Size: 8.05 MB
- Stars: 14
- Watchers: 2
- Forks: 3
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# BTF Rendering
Custom plugin in Python to render measured BTF (Bidirectional Texture Function) with Mitsuba 2.
## Requirement in Python
Make sure that the following libraries are available in python.
- [SciPy](https://www.scipy.org/)
- [BTF Extractor](https://github.com/2-propanol/BTF_extractor)
- [tqdm](https://github.com/tqdm/tqdm) (optional)
## Usage
1. Clone and compile [Mitsuba 2](https://github.com/mitsuba-renderer/mitsuba2). Check whether you can `import mitsuba` in python.
2. Clone this repository and move it there.
```bash
git clone https://github.com/elerac/btf-rendering.git
cd btf-rendering
```
3. Download [UBO2003 BTF Dataset](https://cg.cs.uni-bonn.de/en/projects/btfdbb/download/ubo2003/). Make directory named `UBO2003/` and save the data under there. OR, you can run [download_large_data.py](https://github.com/elerac/btf-rendering/blob/master/download_large_data.py) and the data will download automatically.
Have you placed BTF Dataset as shown below?
```
.
├── UBO2003
│ ├── UBO_IMPALLA256.zip
│ ├── ...
├── custom_bsdf
├── download_large_data.py
├── rendering.py
├── scenes
├── ...
```
4. Run [rendering.py](https://github.com/elerac/btf-rendering/blob/master/rendering.py) and get [rendered image using BTF](https://github.com/elerac/btf-rendering/blob/master/documents/simple_sphere_impalla.jpg).
## Measured BTF (*measuredbtf*)
| Parameter | Type | Description |
| :-- | :-- | :-- |
| filename | string | Filename of the BTF database file to be loaded. The type of dataset is distinguished by its extension. .zip for UBO2003, .btf for UBO2014.|
| reflectance| float | Adjust the reflectance of the BTF. (Default: 1.0) |
| apply_inv_gamma | boolean | Whether to apply inverse gamma correction. If the input is the gamma-corrected image, this process should be applied. (Default: *true*) |
| power_parameter | float | Determine the smoothness of the interpolation. The smaller the value, the smoother it is. (Default: 4.0) |
| wrap_mode | string | Controls the behavior of texture evaluations that fall outside of the [0,1] range. The `repeat` and `mirror` options are currently available. (Default: `repeat`)|
| to_uv | transform | Specifies an optional 3x3 UV transformation matrix. A 4x4 matrix can also be provided, in which case the extra row and column are ignored. (Default: none) |
| | |
| :-: | :-: |
| |  |
| UBO2003 IMPALLA | UBO2014 leather09 |
This custom plugin implements a BTF for rendering reflections of textures taken in a real scene. The BTF is a set of images with different illumination and viewing directions.
`filename` is the name of the BTF database file. This file should follow the format of the BTF dataset of University of Bonn.
Download the [UBO2003](https://cg.cs.uni-bonn.de/en/projects/btfdbb/download/ubo2003/) or [ATRIUM](https://cg.cs.uni-bonn.de/en/projects/btfdbb/download/atrium/) or [UBO2014](https://cg.cs.uni-bonn.de/en/projects/btfdbb/download/ubo2014/) dataset for rendering.
```xml
```
### Interpolation and Power Parameter
This custom plugin interpolates BTF. The interpolation is done by [k-nearest neighbor sampling](https://en.wikipedia.org/wiki/K-nearest_neighbors_algorithm) and [inverse distance weighting](https://en.wikipedia.org/wiki/Inverse_distance_weighting).
The weight of the inverse distance weighting can be adjusted by the `power_parameter` *p*. The parameter *p* determines the influence of the distance between the interpolation points. The smaller *p* is, the smoother the interpolation will be.
The following figures show the difference in appearance when *p* is changed. When *p* is small (*p*=1), the texture is smooth and specular reflection is weak. On the other hand, when *p* is large (*p*=32), the texture has discontinuous boundaries. This is because the angle of the captured BTF data is sparse.
| | | | |
| :-: | :-: | :-: | :-: |
|  |  |  |  |
| *p* = 1 | *p* = 2 | *p* = 4 | *p* = 32 |
## Warning
In the `scalar_rgb` variant, the execution of this plugin is **extremely slow**. Thus, using the `gpu_rgb` variant is recommended.
## Rendered Images from Other Papers
I collected the rendered images from other papers that employ the 3D model of cloth originated at this repository ([`scenes/cloth/cloth.obj`](scenes/cloth/)). These beautifully rendered images enhance the effectiveness of their excellent methods for BTF data processing.
*Kavoosighafi et al., "SparseBTF: Sparse Representation Learning for Bidirectional Texture Functions", Eurographics Symposium on Rendering, 2023. [[Link]](https://diglib.eg.org/handle/10.2312/sr20231123)*
*Dou et al., "Real-Time Neural BRDF with Spherically Distributed Primitives", arXiv, 2023. [[Link]](https://arxiv.org/abs/2310.08332)*
You are free to use my 3D model and scene file of cloth (and also my code) for academic purposes. If you use them, it is not necessary, but I would appreciate it if you refer to my name.