Visible to reflection/refraction and Light exclude option

[DIO]

Any chance we could get the "visible to reflection/refraction" object property in one of the next
releases, as well as the possibility to exclude objects from certain lights?
I´missing these features a lot in studio lighting. These are almost the last missing features that keep
me still using Vray for some scenes.
Are these option difficult to implement? Just asking ...

[rashadcarter]

I doubt this would be possible or advisable in most cases. Unbiased rendering as far as I've read has a very specific meaning related directly to the laws of thermodynamics. Its all based on "reflections," either diffuse reflections or specular reflections. All reflections in theory are specular in basic nature which means that incoming light strikes a surface from a given vector and will be bounced away from that surface by the equal and opposite angle from which it arrived. Diffused surfaces by contrast have micro-bumpiness that tends to scatter the light rays striking it so that the original specular reflection that used to travel away from the surface in one single direction is now being forced to travel in multiple directions leading to the look of matte (dry) surfaces. Also, most every surface in nature has a certain degree of SSS, so the absorbed photons tend to scatter within the medium even if only a tiny bit, which also helps create the look of matte surfaces. Specular surfaces tend to be very smooth and hard with nothing to disrupt the rays as they travel away from the surface and very little in-scattering. It is only at the materials level that the type of reflection is determined.

Path Tracing renders are basically physics experiments which test how "energy" is transferred from one surface to another based on thermodynamic equations. Octane Render factors not only direct diffuse and indirect diffuse reflections, but it also factors direct and indirect specular values as well, which sets it apart from Vray which like most other applications only factors diffuse light and skips specular whenever possible. V-ray, being biased, has the luxury of treating diffuse and specular reflections as unique entities, when in fact, they are not.

Therefore, in Octane, there is very little theoretical difference between diffuse and specular reflections to begin with. There really is no distinction. It is somewhat impossible to make an object visible in a diffuse way and yet invisible in a specular way which is what would happen if you were allowed to make an object invisible to reflections but still participate in the diffuse interactions as you suggest above.

I could well be wrong, I'm no expert by any means. But if what I've read is correct, such options would introduce bias into the results which defeats the purpose of unbiased rendering.

I suggest being willing to depart from the look you achieved in your V-Ray Studio scenes, and realize that Octane renders are more accurate and therefore cannot and will not always look as they do in V-Ray. Your studio lighting approach needs to be updated to work with Octane's physical parameters. less cheating, more legitimate brute force working seems to go well with Octane. I personally like not having to fake things as I used to with other software.

Best of luck.

[DIO]

I´m afraid I don´t share that opinion.
It has nothing to do with having the same look as vray scenes.
I is all about flexibility in the process of making the final picture. And our work isn´t all about realism.
It is about, what the customer wants. And often there is the wish for a little bit of extra specular
on one or two objects, less reflection here or there and so on ...
The customer doesn´t care even if it is 100% unbiased and realistic.

I love octane because of the "realtime" workflow and the quality it produces. With the use of the same
HDR images octane casts more beautiful light than vray, in my opinion.
But nevertheless I always make a lot of Post in Photoshop or After Effects. I use Masks to change the curves,
saturation, exposure of different parts and objects of the image. So the way You see it, I change
the realistic result Octane produces and that way I fake ??
That way the options "visible to camera" and "cast shadow" would be cheating too, because it is not realistic disabling them

May be it is technically difficult or impossible to exclude objects from lights, and making object invisible to reflection, I don´t know that.
But it is definitely not condemnable asking for those options, because it just adds flexibility to the workflow creating the result we want.
Or we should also quit the use of all sorts of Software for Post. Only what the unbiased renderer gives us is vaild?