2d grid evaluation for collision checking

[kleindieck]

Hi!
I am working on trajectory optimization and have a hard time to integrate collision checking given a 2d signed distance field, where each grid cell provides the distance to the closest obstacle.
Is there somewhere an example of 2d table interpolation? I only can find examples referencing the 1d case.

Best,
Jan

[bradbell]

Are you referring to the following example as the 1d case ?
https://cppad.readthedocs.io/latest/interp_onetape.cpp.html

[kleindieck]

Yes! A code snippet for a 2d grid would be great

[bradbell]

This would take me some time to do and I am currently working on other things. Perhaps you would like to to try with my help ?

[kleindieck]

Sure, I can put some work in this. Was just hoping that someone has used cppad for this use case before :)

[bradbell]

Take a look at
https://cppad.readthedocs.io/latest/atomic_four_bilinear.cpp.html

This uses atomic functions, instead of discrete functions, because the discrete functions only take one dimensional arguments.
I only implemented forward mode up to order 1. If you use a higher order forward, reverse mode, sparsity, or base2ad, you will have to implement those.

[kleindieck]

Great, thanks. Will have a look

[kleindieck]

One more question: Is there an example somewhere on how do use the ADFun object when solving with IPOPT (In the FG_eval class)

[bradbell]

See the heading Example on
https://cppad.readthedocs.io/latest/ipopt_solve.html#example

[bradbell]

I suspect that you may need to define more of the virtual functions in atomic_bilinear to get it to work in this context.