How to implement custom shape plugin?

[kimren227]

Hi,

I wish to implement a custom shape plugin, i.e Quadrics. What's the best way of doing that? Hope someone can point me to some starting documents or examples.

My Attemps so far:

• I've implemented the ray-shape intersection logic in dr.jit, and am able to render an image using examples in Dr.Jit's First Steps in Python
• I've read through Mitsuba's custom plugin tutorial, however, I'm not sure what functions I need to implement and can't find a "register_shape()" function in the APIs.
• I've read the source code for "shapes/sphere.cpp", "shapes/cylinder.cpp" etc, them seems all have implemented functions such as "surface_area", "sample_position", etc, are these necessary if I only need solid shape colors (Quadrics may have unbounded surface area)?

Many thanks in advance.

Daxuan

[Speierers]

Hi @kimren227 ,

Currently shape plugins can only be implemented in C++. In order to use your custom shape with OptiX, you will also need to provide a CUDA implementation of the __intersection__myshape() function.

I would recommend you take a look at src/shapes/sphere.cpp and src/shapes/optix/sphere.cuh.

Regarding the implementation of the other methods, those are often necessary to use the shape as an area emitter. You can probably skip those if you are not planning on using it this way.

[njroussel]

Let me add this for completeness:

If you decide that you also want OptiX support for your shape, the current build process is a bit awkward. To point you in the right direction, take a look at resources/ptx/Makefile. This Makefile will generate optix_rt.ptx which has to be generated by hand before the usual CMake build.

[kimren227]

Thanks a lot for these information. I'll give it a shot!