dark interior ambient occlusion

[dmurr]

hi.

i have been using ambient occlusion in vray for sketchup and am very happy with the results i have gotten for exterior architectural renders. i am only able to get a very dark result for interior renders. i understand conceptually why this is happening [the walls, floor, and ceiling are blocking out the ambient "light"] but am not sure which setting to change to fix it. in 3dstudio max there is a setting called 'max distance' that can fix this kind of problem. is there something equivalent for vray? how can i get ambient occlusion to render brighter for interior scenes?

thanks.

i uploaded a jpeg of the interior shot at http://www.sendspace.com/file/egcviw

[Micha_cg]

Re: dark interior ambient occlusion

I'm curious for an answer too. AO should be a nice helper for interiors, where lights cause problems with render time and/or sampling.

[thomthom]

Re: dark interior ambient occlusion

Sorry, the file you requested is not available.

I've not experienced interior renders with AO turning things dark. got a sample model?

[Micha_cg]

Re: dark interior ambient occlusion

So you mean you get a lighting by AO only, like it is the AO standard? What I have seen, ASGvis AO is used in combination with other GI methods only, so that the AO works approx. like DE only. So far I know a full AO need a distance option.

[thomthom]

Re: dark interior ambient occlusion

No - I don't get light from AO. I just get the darker areas near the corners.
I've never used AO in any other software than VfSU. Should one get light from AO?

[Micha_cg]

Re: dark interior ambient occlusion

Yes, that is for what AO can be used and is very useful for quick and clean interior renderings. For example the renderer AIR can't render full GI in high quality, but AO is fast and clean done. Important for interiors is to set a max ray distance. The basic theory is, that at each sampling point rays are send in the space. If the ray hit an object, the sample ray is calculated as black, if nothing is hit, than white. If the user set max distance 1m and the room is 2m high, than only in the edges and around object a darkening is visible, because if after 1m sampling ray nothing is hit, than it is calculated as white. Without a distance option every ray hit the wall and the sampling point is set black. At my example I use max distance 300cm.

[fpedrogo]

Re: dark interior ambient occlusion

I'm not sure if the option that you are looking is the radius, basically this control the distance of the AO. If not, you could make a AO pass using Dirt and there you will have more control of the AO.
I exaggerate the AO effect.

First image Radius = 10, second image Radius = 50

http://img510.imageshack.us/img510/7007/aor50.jpg

Best

[Micha_cg]

Re: dark interior ambient occlusion

Thank you, interesting experiment.

I would prefer a simple full AO, but I looked around at the www now and if I understand right, Vray dosn't support the classical AO. The dirt material seems to be the only way. Looks like a lot of work, if many materials/textures are used. Also the edges are so extreme dark.

[thomthom]

Re: dark interior ambient occlusion

Thank you, interesting experiment.

I would prefer a simple full AO, but I looked around at the www now and if I understand right, Vray dosn't support the classical AO. The dirt material seems to be the only way. Looks like a lot of work, if many materials/textures are used. Also the edges are so extreme dark.

Instead of Dirt material, enable Material override and render with AO. Exclude the window material from the material override.

[andybot_cg]

Re: dark interior ambient occlusion

That's an interesting idea fernando. It would be quick to do if you use a global material render - and then use the result as a layer in pp (where you could also set the strength of the effect.) I'm assuming that's what you are suggesting, to do just like an AO pass, except with the dirt material.

Um, by the way, is there a way to set an override material like there is in 3dsMax? Right now, it looks like the only way to do this is to use the global material change plugin in Sketchup and replace all the materials with a dirt material. Is that so?

-Andy

[fpedrogo]

Re: dark interior ambient occlusion

I would prefer a simple full AO, but I looked around at the www now and if I understand right, Vray dosn't support the classical AO. The dirt material seems to be the only way. Looks like a lot of work, if many materials/textures are used. Also the edges are so extreme dark.

I exaggerate the effect on purpose.

Instead of Dirt material, enable Material override and render with AO. Exclude the window material from the material override.

You also can use any material on the override option.

Ever want to override all of the materials in your scene, with a particular material in your material editor, rather than just some silly diffuse color? Well my friends, you're in luck! As of 1.48.66, you should be able to achieve this effect by simply naming one of your materials "VRayOverrideMaterial". That is the name of the material that we use to override all materials in your scene, when you enable "override materials" in the Global Switches section of your Options Editor.

This effect is actually the result of an unintentional bug, but I stumbled across it while trying to add this feature on purpose. Hooray for bugs that work in the user's favor!

So, If you make a dirt material for the ambient occlusion past and rename that material as "VRayOverrideMaterial", and enable the override option on the Global Switches, you will have a better Ambient Occlusion past. This is more complex, but you will have more control over the AO.

Best

[fpedrogo]

Re: dark interior ambient occlusion

Um, by the way, is there a way to set an override material like there is in 3dsMax?

Yes, I answered the question in the previous post.

Also here is the original link

http://forum.asgvis.com/index.php?topic=8655.0

[andybot_cg]

Re: dark interior ambient occlusion

Thanks Fernando, I had a vague memory of reading that somewhere. Easy enough! and much better than messing with SU materials!!

[andybot_cg]

Re: dark interior ambient occlusion

Looks like the whole AO and dirt material conversation veered off the original post. I re-read and think I understand what was asked originally. Is there a way to render an interior without GI or lighting just by setting an occlusion value somehow. It seems the answer is no. All the answers so far above rely on having GI turned on.
Is this what you were asking dmurr?

[thomthom]

Re: dark interior ambient occlusion

Instead of Dirt material, enable Material override and render with AO. Exclude the window material from the material override.

You also can use any material on the override option.

??? I can only select a colour for the global material override. You got some special super-secret version?