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Prism and laser - no caustics!??
Posted: Thu May 29, 2014 10:16 pm
by nuno1980
Hi.
I have OR 1.5 demo.
Scene:
-Laser (blue)
-Prism (dispersion with 1/3 and IOR 1.5)
Realistic is good using LuxRender (bidirec-MLT) for Blender running CPU only:
See image
In OR with PMC kernel setting default except rejects 10k, caustic blur 0.0 and parallelism 1:
No caustics?! - it seems unrealistics...
Prism hidden - it's realistic.
NOTE: current OR doesn't have "fog volume" support until new OR 2.0.
Therefore, should fix soon my issue (maybe 2.0).
Download "Prism demo" OBJ (laser IES included) in bottom.

Re: Prism and laser - no caustics!??
Posted: Thu May 29, 2014 10:29 pm
by nuno1980
OOh. I forget wireframe...
wireframe about ball light is for laser

Re: Prism and laser - no caustics!??
Posted: Sun Jun 01, 2014 10:25 am
by nuno1980
Do you confirm my issue??
Re: Prism and laser - no caustics!??
Posted: Wed Jun 04, 2014 2:38 am
by FooZe
Hi Nuno,
I have tweaked the light source and setup all the materials (see attached zip).
Here is the render after some time:
The most important changes were to the emitter. It's important in octane to make emitting surfaces as low poly as possible so I made it a plane.
Also, a bar works better than a dot for this (at least this is what I remember using in physics class

).
I have added a slight fog - this
DOES work in 1.50
I left in 0.010 caustic blur, this is not enough to ruin the dispersion effect, and helps show the caustics a lot better/quicker. Parallelism was changed to 1, max rejects unchanged at 500.
Hope this helps.
Thanks
Chris.
Re: Prism and laser - no caustics!??
Posted: Wed Jun 04, 2014 9:10 am
by nuno1980
Ok. I want
dot light (= laser).

But I can appear caustics from bar light horizontal, using caustics blur 0.0.
How do I enable fog volume?

Re: Prism and laser - no caustics!??
Posted: Wed Jun 04, 2014 10:05 pm
by FooZe
The fog is created by a cube surrounding the scene that has a specular material applied with the following settings:
1) Index 1.0
2) 0 reflection
3) full transmission
4) Scattering Medium with enough scattering to generate the amount of fog you want. (So tweak the Medium's Scale attribute to dial in more or less fog.)
It is important to note that you cannot have the camera inside this fog cube or it will not work. Note how the material picker will always choose the fog cube because that's what is in front of the camera. If you want to pick the prism or other materials in the scene you will need to right click when material picking.
Thanks
Chris.
Re: Prism and laser - no caustics!??
Posted: Wed Jun 04, 2014 11:21 pm
by nuno1980
FooZe wrote:The fog is created by a cube surrounding the scene that has a specular material applied with the following settings:
1) Index 1.0
2) 0 reflection
3) full transmission
4) Scattering Medium with enough scattering to generate the amount of fog you want. (So tweak the Medium's Scale attribute to dial in more or less fog.)
It is important to note that you cannot have the camera inside this fog cube or it will not work. Note how the material picker will always choose the fog cube because that's what is in front of the camera. If you want to pick the prism or other materials in the scene you will need to right click when material picking.
Thanks
Chris.
I have done but you choose to create box (rectangle or cube). Thank you!
My case is very hard for PMC kernel due to the dot or point light source - to appear hardly "sharper" caustics.

But it has "new" caustic sampler, for iray or Thea Render...

Re: Prism and laser - no caustics!??
Posted: Thu Jul 17, 2014 9:47 pm
by nuno1980
NEW EVGA GTX 580 with 3GB edition

(EVGA GTX 480 died to RMA -> new GTX 670 but I'm not interested 670 due to worse CUDA optimization)
New OR 2.02 demo but still max 256k-sample.

132k-sample and no caustic blur.
I want 2M-, 4M- or unlimited sample for newer version of OR, ok?
Re: Prism and laser - no caustics!??
Posted: Tue Jul 22, 2014 11:10 pm
by nuno1980
@FooZe or moderator: please should answer my question (my previous post).