Adding lenses to the mix

[lbreede]

I've dabbled in physical lens emulation in Houdini and I wonder if there's a standard for lens characteristics like distortion, vignetting etc.
USD wise, it can probably be a focal length override on the camera, but I imagine the simulation is different from renderer to renderer. I've only ever tried the Karma physical lens shader. Just food for thought :)

[AntonPalmqvist]

Unfortunately there doesn't seem to be any standard just yet. As you say, it varies from renderer to renderer what kind of lens characteristics you can use.

Blender, for example, uses 4th degree polynomials for lens distortion, while the data you get from databases such as Lensfun is not compatible with that format.

Other interesting links on the subject. However, none of them seem to have converged around a standard:

• http://zenopelgrims.com/project-polynomial-optics-arnold.html
• https://docs.chaos.com/display/VMAYA/Lens+analysis+tool
• https://www.panotools.org/dersch/barrel/barrel.html
• https://www.lentil.xyz/index.html#features
• https://github.com/hanatos/lensoptics

I'm hoping to expand the database with this kind of data, so please let me know if you have additional resources on this topic!

[lbreede]

yeah I'd usually point to Zeno's Lentil work. It's the best. The Karma Physical Lens Shader is getting better and better and runs on the GPU finally :)

[lbreede]

If you look at my fork you can see that there were tests that ran for every push and PR. Number 5 failed for example because changed a sensor size to be a list of three numbers. Therefore:
test_sensorSizes self.assertEqual(len(size), 2) AssertionError: 3 != 2