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I am trying to calculate the laplacian of a scalar field but I might actually need something else. So basically I am applying reaction diffusion on a 2d image. I am reading the neighbours, multiplying them with these weights and then add them.

This works great. I don't know if what I am doing is called laplacian but I was told that it is.

Now I am trying to do the same thing in 3d volumes:

http://www.openvdb.org/

But the problem is I don't know what weights to use to sum the neighbours. If I use the same weights on a 2d volume, it works just the same. But in 3d, I am not sure what the weights would be.

I also tried using actual laplacian (OpenVDB has tools to calculate it), but after 7-8 iterations the values in the volume go to infinity. Maybe what I need is not really laplacian. But whatever is coming from the neighbours has to be in balance so just like in the 2d image version, the values don't get bigger and bigger while nothing is getting smaller. That's my understanding.

I tried calculating the laplacian manually also by using the actual definition, and got different result that the build-in tools. Not sure if I am missing something:

http://paste.ofcode.org/QYUec5tu63AM6n2Bmax6C7 [Broken]

Do you guys know what I need?

Cheers :)

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# How to get the laplacian of a scalar field?

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