chromatic aberration with VRay

[kosso_olli]

Also for Arnold - https://lentil.xyz/

Something like this is exactly what I need in V-Ray!

[kosso_olli]

Anyone with camera shader experience in VRay? is CA possible with it?

This is what the docs for Lentil say regarding CA: "Lentil is a spectrally-plausible system. But since Arnold is an RGB renderer, we render at a single wavelength.

Note that one *could* render the same image 3 times with different wavelengths and combine them (1 for each channel) into an image with physically plausible chromatic aberration."

The changelog also show CA in action here: https://lentil.xyz/docs/changelog.html#2.4

[piotrus3333]

This is what the docs for Lentil say regarding CA: "Lentil is a spectrally-plausible system. But since Arnold is an RGB renderer, we render at a single wavelength.

Note that one *could* render the same image 3 times with different wavelengths and combine them (1 for each channel) into an image with physically plausible chromatic aberration."

The changelog also show CA in action here: https://lentil.xyz/docs/changelog.html#2.4

the changelog linked shows axial chromatic aberration. I was rather referring to lateral ca, somewhat more commonly used in cgi (fringing intensifies from the center of frame outwards).

[kosso_olli]

Well, in the examples the fringing is more intense on the edges, no?

[piotrus3333]

Well, in the examples the fringing is more intense on the edges, no?

yes, it does. but it is different type of aberration than for example this:

[kosso_olli]

The type of CA shown in Lentil would be fine for me. Plus all the other nice features.

[piotrus3333]

axial chromatic aberration setup:

[kosso_olli]

Looks good! One of our interns also did an experiment with raytracing a real camera system; some results are below. We still haven't decided if we want to put this into V-Ray officially or just dump it on Github.

Best regards,
Vlado

Did you ever conclude?
I was reminded of this while watching a video where something similar was done in UE. The real bloom was particularly nice because it was not added as kind of a post-effect:

https://youtu.be/2SsTk657Uw0?si=rBSrf6b59Y3aUnq-&t=172


Oh, and Lentil is now open source: https://github.com/zpelgrims/lentil

[flat]

Lens Sim for Blender has just been released.
I think this is the ideal implementation.

V-Ray Blener....

[kosso_olli]

Lens Sim for Blender has just been released.
I think this is the ideal implementation.

V-Ray Blener....

Wow, this is amazing!

[kosso_olli]

I wonder if something similar could be done with V-Ray/3dsMax

[vlado]

Yes, we did write a lens simulator for V-Ray some years ago. It works fine but is somewhat slow to render. However if this is of interest, we can certainly release it officially.

Best regards,
Vlado

[bardo]

Yes, we did write a lens simulator for V-Ray some years ago. It works fine but is somewhat slow to render. However if this is of interest, we can certainly release it officially.

Best regards,
Vlado

About increased rendertimes, the author of the addon for Blender reported this in its documentation page:

"From my experience tracing the lens seems to add a constant amount of extra render time per sample. On simple scenes the render time will be quite slow compared to the standard camera, since the extra time tracing the lens might be greater than the time it takes to trace the scene. On larger scenes with thousands of objects the slowest part will be traversing the scene, so the performance hit will be relative small. When doing animations you will in general get more noise with Lens Sim cameras, so the render might require more samples to get the same results as the standard camera. If I should take a guess I think a render time multiplier of 1.2-3.0 is realistic, but it is hard to say due to the amount of render factors we have to consider. Additionally, bigger and brighter bokeh shapes are hard to get noise free since the bokeh sample distribution might be uneven on some lenses, especially in animations, so keeping it as a subtle effect is recommended."

Have you experienced something similar?

[^Lele^]

About increased rendertimes, the author of the addon for Blender reported this in its documentation page:

"From my experience tracing the lens seems to add a constant amount of extra render time per sample. On simple scenes the render time will be quite slow compared to the standard camera, since the extra time tracing the lens might be greater than the time it takes to trace the scene. On larger scenes with thousands of objects the slowest part will be traversing the scene, so the performance hit will be relative small. When doing animations you will in general get more noise with Lens Sim cameras, so the render might require more samples to get the same results as the standard camera. If I should take a guess I think a render time multiplier of 1.2-3.0 is realistic, but it is hard to say due to the amount of render factors we have to consider. Additionally, bigger and brighter bokeh shapes are hard to get noise free since the bokeh sample distribution might be uneven on some lenses, especially in animations, so keeping it as a subtle effect is recommended."

Have you experienced something similar?

you left out important parts, though:

Further, not all noise is equally expensive to clean, so providing for general metrics blindly is impossible.

Assume it will seriously pull the handbrake on your rendertimes, and that you will have to resort to tricks and/or workarounds if you plan on producing with it rather than to test.
In other words, unless you're cool with a few times the rendertime of current DoF, you can safely ignore the tech (like most production renderers' cameras do.).

On the samples page, notice how the stuff that renders slightly slower is terminally simple for lighting and shading, whereas the moment complex shading is introduced (the old man, and SSS), rendertimes triple.
If the complex stuff is out of focus and producing Bokehs, then things may well get much worse, even with highly optimised code.

[piotrus3333]

fetch (1920×960)

it wouldn't be that slow in VRay. this was few years ago, rendered on 3090. RTX was quite a bit faster back then with lenses. if you setup things to get effects you need (using tools available in VRay like lens files, bokeh occlusion etc) and don't render through 5 refractive elements those looks are totally feasible in a timely manner.