Ambient Occlusion vs Dirtmap

[GALACTUS]

This is what I was trying to achieve.


This is straight from max, no comping of dirt passes.

There are 2 lights, 1 is the key light which is casting the strong shadows and the 2nd light is switched of but is projecting the ambient occlusion shader unto the scene, there by letting us render out the individual material colours and also you can see from the glass objects that the AO is visible through and the objects themselves cast shadows and the AO will be visible in the reflections in 1 pass.

This is what I am trying to achieve in VRay, yes I know there are other ways of getting to this, but there is no GI involved and works on interiors and animated objects too.

[Neilg]

Ive said twice to do it with a mix map in your material and so has Da_elf. Please read the thread.

Does exactly what you want, dont even need any lights or GI and youve got far more control.

[GALACTUS]

I know you have said it twice and so has Da_elf. I am probably slow on the uptake, but with a mix map dont you have to apply it to all your materials in the scene individually? if so then you have missed my point. I put the AO shader in 1 light and regardless of what I build/merge or change I do not have to fiddle with or add to that map. It is like a material override that overlays data through out your scene, but still enables you to see through to the underlying geometry texture data. Where as the way I understand the mix map method if i merge or create new scene information I have to manually "mix material with vraydirt in the amount slot, then your bitmap in the white and either a darker version or a different one altogether in the other" Yes I do know you can do it in VRay as shown below, but not controlled the way i suggest.

The VRay version


You do realise that you dont have to respond to this thread if it displeases you, it is of particular interest to me and I like to explore it further. For those interested you can download the scene from the link below, which elaborates my point more clearly.



mental ray
www.e3di.co.uk/test/AOmrtest.rar

vray
www.e3di.co.uk/test/AOVraytest.rar


Thank you all for your responses so far.

Colin

[joconnell]

We could pobably modify my colour correct script to apply a vray dirt map to the diffuse of every mat and put the previous diffuse in the white slot of the dirt - not perfect but might speed things up a tad.

[CCS]

Looking good. Up the subs and you'll look the same as the MR version.

I like the override version too. Yes, it's another step in post, but it saves a *lot* of screwing around with materials. Would be slick if in additional to "Override" there were an "Overlay" button.

[GALACTUS]

Hear hear, I would hate to fiddle with materials in a complex or large scene. Bring on the ubiquitous "material overlay" button

[RErender]

For extriors with one key light the projector light method looks like it might be doable. Great idea I would never have thought that would work.

[studioDIM]

For an exterior, you could probably figure out how large your scene bounding box is and set it to its diagonal length if you want to be sure you're sampling the entire exterior.

Aside from the superb divulgant description of a very bitchy technical issue, i'd like to say i smell a script coming...


Lele

[vlado]

For exteriors in particular, you are way better off using the V-Ray light in dome mode. The results can be very similar.

Best regards,
Vlado

[stilgarna]

For exteriors in particular, you are way better off using the V-Ray light in dome mode. The results can be very similar.

Best regards,
Vlado

I don't want to be rude but I think that Vray light in dome mode is very slow compare to VrayDirt...

And option in the VrayMtl to add dirt is welcome...

Best regards...

PS : Vlado you do a great job...

[Neilg]

And option in the VrayMtl to add dirt is welcome...

Welcome as in you would like the feature?...

Thats what its for.

[vlado]

And option in the VrayMtl to add dirt is welcome...

Put VRayDirt in the diffuse slot and check its "Affect alpha" option.

Best regards,
Vlado

[plastic_]

i have some kind of non-destructive auto-override script here:

http://plugins.angstraum.at/vrayao/manual.htm

but it uses skylight/dome, not AO shader.
and it makes everything white.
i may update it...looks interesting with the colors.

[plastic_]

that mental ray scene is great i think.
nice setup for quick visualisations.
why dont you just use mental ray?

[GALACTUS]

No proxies in mental ray and prefer VRay shaders and handles large scenes better than mental ray straight out of the box.