Calculating Volume Density with Python?

Coding Python Support
1

Does anyone have experience using a Python script to compute volumetric density for an arbitrary mathematical function?

I’ve build a Node Tree to create a Gaussian density distribution (density = constant * exp(-r^2)) for a cube filled with volumetric emission material in Cycles. It works just fine, but it’s a rather indirect way to do something in a few lines of code. I’ve attached the .blend if you care to look. I haven’t gone to the trouble of making a custom node group, but that would be my next step if I continued with the Node route.

Thanks!

Attachments

density-calculation.blend (464 KB)

2

I think that you would achieve what you’re looking for using OSL instead:

shader VolumeShaper(
output closure color CL = holdout()
){
float D = 0.1exp(pow(-length(sin§),2));
CL = emission()(pow(D,10))0.1color(1,1,1);
return;
}

Here’s a screenshot comparing the above script with your node setup and live result:

screennode01.png1901×1019 262 KB

3

Thanks tree3d!

You’ve just opened up a whole new world for me! I had seen some discussion of OSL, but those articles were at a very high level. I got the impression that OSL was beyond me. I did a little looking around and found www.openshading.com and Gottfried Hofmann’s articles on Blender Cookie.

Do you have any favorite resources or documentation on OSL? I’d love to hear about them.

4

Hello!

I’m glad i could help!

Well… Since OSL+CYCLES+BLENDER is kind of a new thing (2 years) i could not find alot of solid information to start with BUT:

Vray supports OSL so you can get useful information from them: http://docs.chaosgroup.com/display/VRAY3/OSL+Support+in+V-Ray

http://blendersushi.blogspot.pt/2013/10/osl-circle-scatter-and-bombing-part-two.html - Blendersushi has great info about OSL and also something about porting RENDERMAN OSL scripts!

Above all my true guide is the OSL language spec : https://github.com/imageworks/OpenShadingLanguage/blob/master/src/doc/osl-languagespec.pdf -This along with the above and all the help you can get here should set you on the path to OSL enlightenment!

5

Thanks again! I’m excited to dive into OSL!