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I'm not sure where they're getting that "lenses in pathtracers are ignored". They most certainly are not. How would physically based path tracing even work if t

I'm not sure where they're getting that "lenses in pathtracers are ignored". They most certainly are not. How would physically based path tracing even work if they were? e.g. https://blog.demofox.org/2018/07/04/pathtraced-depth-of-field-bokeh/ https://blog.demofox.org/2018/07/04/pathtraced-depth-of-fiel...

joshuak 6y ago
Traditionally most cg rendering systems use an idealized lens to simplify the math. Matrix projection transformations simulate a pinhole lens. This does mean that all images are perfectly sharp however, so for depth-of-field, bokeh, and other realistic lens blurring effects the position of the idealized lens (i.e. virtual pinhole) is varied over samples creating a sort of fuzzy pinhole.
Dork1234 6y ago
Most commercial renderers that I know of just render via simulating a pin-hole camera. Any Camera lens effects, lens flare, bokeh is just simulated off of the very simple pin-hole model. The method in Lentil appears to be actually trying to simulate the ray bounces internal to the camera lenses via the geometry from patent information. I am not an expert on optics, but from what I know about modern lens design are these elements are coated to change reflection and designed to prevent optical problems that don't exist in most computer renders (Chromatic Aberration). My initial take is this simulation incorrectly solves a problem that most users rendering things have no interest in even dealing with. Computer rendering has moved into this simulating the physical world but without asking why, in many rendering cases you do not want a camera that behaves like the physical world, you want it to behave better and with less control.
- ladberg 6y ago
  I think most commercial renderers offer a thin lens model in addition to pin-hole to get DoF and custom bokeh, but using a real multi-lens setup gets you some more realistic effects.
- zeta0134 6y ago
  The main use case that popped in my head was compositing of rendered effects with live footage from a physical camera. In this case, might it be beneficial for your render to exactly match the real world lens, defects and all?
  - CyberDildonics 6y ago
    It is typically done in compositing since it is impractical to render with depth of field which gives you a lot more noise and takes away your ability to change it without a re-render.
alkonaut 6y ago
I think it means lens thickness and design imperfection is "ignored". The renderer typcially uses a simple aperture + perfect thin-lens approximation.

joshuak 6y ago

Traditionally most cg rendering systems use an idealized lens to simplify the math. Matrix projection transformations simulate a pinhole lens. This does mean that all images are perfectly sharp however, so for depth-of-field, bokeh, and other realistic lens blurring effects the position of the idealized lens (i.e. virtual pinhole) is varied over samples creating a sort of fuzzy pinhole.

Dork1234 6y ago

Most commercial renderers that I know of just render via simulating a pin-hole camera. Any Camera lens effects, lens flare, bokeh is just simulated off of the very simple pin-hole model. The method in Lentil appears to be actually trying to simulate the ray bounces internal to the camera lenses via the geometry from patent information. I am not an expert on optics, but from what I know about modern lens design are these elements are coated to change reflection and designed to prevent optical problems that don't exist in most computer renders (Chromatic Aberration). My initial take is this simulation incorrectly solves a problem that most users rendering things have no interest in even dealing with. Computer rendering has moved into this simulating the physical world but without asking why, in many rendering cases you do not want a camera that behaves like the physical world, you want it to behave better and with less control.

ladberg 6y ago
I think most commercial renderers offer a thin lens model in addition to pin-hole to get DoF and custom bokeh, but using a real multi-lens setup gets you some more realistic effects.
zeta0134 6y ago
The main use case that popped in my head was compositing of rendered effects with live footage from a physical camera. In this case, might it be beneficial for your render to exactly match the real world lens, defects and all?
- CyberDildonics 6y ago
  It is typically done in compositing since it is impractical to render with depth of field which gives you a lot more noise and takes away your ability to change it without a re-render.

alkonaut 6y ago

I think it means lens thickness and design imperfection is "ignored". The renderer typcially uses a simple aperture + perfect thin-lens approximation.