Ambient Occlusion vs Dirtmap

[Neilg]

Is this ray shooting method the reason why its so hard to get true black through the vray dirt then?

Galactus: I dont know if its what youre after, but try a 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. I never use dirt as a seperate pass, its all done within my materials so Ive got more control over the radius/depth on specific objects. Works a dream on animations.

[Da_elf]

...... appears to simply be a direct relationship of surface proximity and not a measure of whether or not a surface can "see" the ambient area. Good to know.

actually the whole ambient occlusion thing is kind of a wrong name. since all AO shaders calculate the relationship of distance, not the relationship of viewing ambient light. basically what your might be refering to is just an ambient pass with 1 bounce.

http://en.wikipedia.org/wiki/Ambient_occlusion

perhaps the most straightforward way is to use the Monte Carlo method by casting rays from the point p and testing for intersection with other scene geometry (i.e., ray casting)

[artur.leao]

One thing that would be cool was to have another "Affect alpha" were the black (Occluded Color) appear as 1 in the alpha (as white) and the white (Unoccluded Color) appear as 0 in the alpha (as black). Long story short story, it would be cool to have the possibility to do an AO pass that had Alpha, like in MR (at least on XSI).

[jonnybefree]

i think when you have an ao pass, while its b&w, you dond't need to have an alpha.

[artur.leao]

Well, depending on the layer mode (Screen, Multiply or whatever) if you have the alpha, you can control the intensity of the occluded color without affecting the areas of the unoccluded color. A director that worked with me, asked me that on a recent project, that's why I'm asking.

[dejaVu]

One thing that would be cool was to have another "Affect alpha" were the black (Occluded Color) appear as 1 in the alpha (as white) and the white (Unoccluded Color) appear as 0 in the alpha (as black). Long story short story, it would be cool to have the possibility to do an AO pass that had Alpha, like in MR (at least on XSI).

Couldn't you just duplicate the AO pass and invert it to get the Alpha you need?

[Candelero]

'almost' black (maybe like 254,254,254).

You would need some INVERSE glasses to see the black like that.

Best regards,
nikki Candelero

[GALACTUS]

How about a method of projecting the VRay Dirtmap unto the scene without using the material override feature, that way we can render the dirtpass over the top of our scene in one pass. I am able to do this using the MR AO material and have seen it done with turtle.

I know this means a lack of flexibility later on, but it does negate the need to comp the dirtpass later.

Colin

[Da_elf]

why not use the AO render as a luminance alpha controling another layer. for instance you can tint that other layer, increase intensity etc and the luminance map AO render will controle where that other layer is being placed

[artur.leao]

One thing that would be cool was to have another "Affect alpha" were the black (Occluded Color) appear as 1 in the alpha (as white) and the white (Unoccluded Color) appear as 0 in the alpha (as black). Long story short story, it would be cool to have the possibility to do an AO pass that had Alpha, like in MR (at least on XSI).

Couldn't you just duplicate the AO pass and invert it to get the Alpha you need?

Well, yes but wouldn't it be better if Vray had that "simple" option ? Cya.

[GALACTUS]

If you do it as a projected map you only need it in one place and you dont have to edit loads of object materials or indeed add it to any new materials you create. In mental ray you can create a light, turn it off and put the AO material into the mentalray light shader section of the light, which then projects that info unto the scene.

It just seems to be an easy way of doing it especially with large scenes.

[Da_elf]

How about a method of projecting the VRay Dirtmap unto the scene without using the material override feature, that way we can render the dirtpass over the top of our scene in one pass. I am able to do this using the MR AO material and have seen it done with turtle.

I know this means a lack of flexibility later on, but it does negate the need to comp the dirtpass later.

Colin

use the dirt pass in a mix map

[GALACTUS]

I will give it a shot dude

[Neilg]

Well, yes but wouldn't it be better if Vray had that "simple" option ? Cya.

To be honest i'd prefer it if vlado spent his time coding more useful things.

This thread has given me such a bad headache, its a disaster.

[artur.leao]

Lol relax and I think it's the artist who makes it usefull or not. I did missed that option but of course there are priorities, either way it's good to give our feedback to Chaosgroup Cheers