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    "description lang=en": |
      Top-level documentation for DRTK.
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# DRTK – Differentiable Rendering Toolkit

DRTK is a Python package built on top of PyTorch, offering differentiable rasterization functionality.
We focus on rasterization due to its speed, providing functionality which is typically common in real-time graphics, while leaving shading and lighting/material models for user implementation.

Rasterization is a widely used rendering technique due to its speed and efficiency, especially for real-time applications.
However, it presents challenges when used in differentiable rendering pipelines, particularly at visibility boundaries, where non-differentiable operations, such as discrete pixel coverage and occlusions, occur.
DRTK implements a novel approach to computing gradients at these visibility discontinuities described in [**Rasterized Edge Gradients: Handling Discontinuities Differentiably**](https://arxiv.org/abs/2405.02508), overcoming the limitations inherent in rasterization’s fixed-grid structure and z-buffering.
DRTK keeps the rasterization process intact and efficient while enabling gradient propagation through occlusion boundaries and geometry intersections.
DRTK provides a set of differentiable components to build custom differentiable rendering pipelines, like the following:

{bdg-primary-line}`model` → {bdg-primary}`transform` → {bdg-primary}`rasterize` → {bdg-primary}`render` → {bdg-primary}`interpolate` → {bdg-warning}`CUSTOM SHADING` → {bdg-primary-line}`rendered image` → {bdg-primary}`edge_grad` → {bdg-warning}`LOSS FUNCTION`

* **transform**: Projects 3D vertex positions onto the image plane of the camera.
* **rasterize**: Performs rasterization, mapping output pixels to triangles.
* **render**: Computes depth and barycentric images.
* **interpolate**: Interpolates arbitrary vertex attributes.
* **edge_grad**: Computes gradients at discontinuities.
* **CUSTOM SHADING** and **LOSS FUNCTION**: User-defined components for shading and loss calculation.

```{video} _static/teaser_video.mp4
  :loop:
  :autoplay:
  :class: full-width
```
Fitting of a simple hand model with simple lambertian material to a single photo. See tutorial [Single Image Hand Fitting](tutorials/DRTK_Tutorial_hand_fitting).


## Hello Triangle!

Here's a simple "Hello Triangle" example with DRTK:
```python
import drtk
import torch as th
from torchvision.utils import save_image  # to save images

# create vertex buffer of shape [1 x n_vertices x 3], here for triangle `n_vertices` == 3
v = th.as_tensor([[[0, 511, 1], [255, 0, 1], [511, 511, 1]]]).float().cuda()

# create index buffer
vi = th.as_tensor([[0, 1, 2]]).int().cuda()

# rasterize
index_img = drtk.rasterize(v, vi, height=512, width=512)

# compute baricentrics
_, bary = drtk.render(v, vi, index_img)

# we won't do shading, we'll just save the baricentrics and filter out the empty region
# which is marked with `-1` in `index_img`
img = bary * (index_img != -1)

save_image(img, "render.png")
```

![hello triangle](/_static/hellow_triangle.png)


## Installation
To build and install the DRTK package as a wheel:
```
pip install wheel
python setup.py  bdist_wheel
pip install dist/drtk-<wheel_name>.whl
```

For in-place builds, useful for development:
```
python setup.py build_ext --inplace -j 1
```


## Requirements
Cure dependencies:
* CUDA Toolkit
* PyTorch (>= 2.1.0)
* numpy

Some examples and tests may also require:
* torchvision
* opencv-python

## Contributing
See the [CONTRIBUTING](https://github.com/facebookresearch/DRTK//blob/main/CONTRIBUTING.md) file for how to help out.

## License
DRTK is MIT licensed, as found in the [LICENSE](https://github.com/facebookresearch/DRTK//blob/main/LICENSE) file.

## Citation
When using DRTK in academic projects, please cite:
```bibtex
@article{pidhorskyi2024rasterized,
  title={Rasterized Edge Gradients: Handling Discontinuities Differentiably},
  author={Pidhorskyi, Stanislav and Simon, Tomas and Schwartz, Gabriel and Wen, He and Sheikh, Yaser and Saragih, Jason},
  journal={arXiv preprint arXiv:2405.02508},
  year={2024}
}
```

```{toctree}
:glob:
:maxdepth: 2
:hidden:

installation/index
```

```{toctree}
:glob:
:maxdepth: 2
:hidden:

tutorials/index
```

```{toctree}
:glob:
:maxdepth: 2
:hidden:

api_reference/index
```

```{toctree}
:hidden:

GitHub <https://github.com/facebookresearch/DRTK>
```