specular reflection off mirror

[loeffler]

How can I achieve a very simple thing:

A light (rhino directional light source)hits a mirror (steel shiny?) and the light that is reflected creates a light patch on a wall (standard vray mat)?

what render settings do i have to use?
what material for the mirror?

I just cannot get it to work - help very much apreciated!!

[skysurfer]

Re: specular reflection off mirror

If I understand well your question, the solution it's to enable the Caustics (in the Options windows).

Riccardo

[loeffler]

Re: specular reflection off mirror

thank you for your reply. Thats what I thought but even with caustics on it doesnt work. there are of course many variables - in the settings as well as in the material. what else could be wrong?

[Micha_cg]

Re: specular reflection off mirror

Did you have seen the caustic tutorial at the ASGvis support pages?

[loeffler]

Re: specular reflection off mirror

Yes I did check it - actually I can make it work with a point light source (like in the tutorial)but not wit a directional light. Also with a rectangular light source it doesnt work (I guess then it is using gi caustics which dont help me). My problem is that I need parallel light to do my reflective caustics physically correct - what can I do?

[dalomar_cg]

Re: specular reflection off mirror

In vfr, parallel lights are infinite. Basically, the only thing that matters when you set a direct light is the direction (vector). The position/location of light is not taken to account. Therefore, caustics cannot be generated from parallel lights because there is no source to shoot photons from.

I'm not sure why you need parallel lights for a "physically correct" result because they are not physical light sources. I would highly suggest point lights for caustic usage. If you must use a directional light and you need to generate caustics, then you can try using a v-ray sun with some major tweeking. The vray sun, for caustics calculations only, will take into account the location of the light and the scale of the scene.

I think it might be good to post a reference image as to the affect that you are trying to achieve. I'm just not really getting what you're after.

[Micha_cg]

Re: specular reflection off mirror

Parallel light and caustic could be a general render problem, because the photons should be limited to an area and not spread over an unlimited area like it the dir light do. I think, there should be a radius option ... and if I look here, I see one.

http://www.spot3d.com/vray/help/150SP1/light_params.htm

[dalomar_cg]

Re: specular reflection off mirror

That is why you can do caustics with sun...because it has a radius a distance for the emitter. Its actually more of a problem with photon mapping that with the direct light itself (although it can be resolved through an implementation similar to the Sun), since photon mapping is limited in the kinds of light sources that it can simulate. GI, for instance, cannot be calculated with photon mapping

Shooting Methods:
Disadvantages-
Cannot simulate efficiently all kinds of light effects e.g. object lights and environment lights (skylight); non-physical light sources are difficult to simulate.

http://www.spot3d.com/vray/help/150R...hods.htm#part2

[loeffler]

Re: specular reflection off mirror

Thanks everyone for the comments.
My problem is partly solved. The v-ray sun does produce the desired reflections in some cases - in others it doesnt. The thing I am trying to do is a grid of mirror(chrome) surfaces in front of a window. the sun is reflected and draws patterns onto the interior walls. depending on the angle of the sun the light is sometimes reflected twice or more times between the louvers before it foes into the space. It looks like v-ray is only producing the patches if the light is reflected once. I dont see any setting that allows me to control the number of reflections in caustics - or is there something like that? Advise appreciated!

[dalomar_cg]

Re: specular reflection off mirror

I'm not 100% sure on this, but I believe that the number of bounces for caustics calculations will reference the max depth amount. The default is 2, so that would make sense if you're not getting as many as you think should be there. Thats just an educated guess though.