AO pass directly on top of beauty pass ?

[nmn]

Hi everyone,

the question is can we obtain an image with the beauty pass and AO pass composited directly out of 1 render (without passing through cops? )

in fact at first i thought it was straightforward, using the vex global illuminatin on a light template, but either i'm doing smtg wrong here or there is smtg i didn't really understand.

when we use the vex GI node with it set to ambient occlusion i see no AO, unless i use like a white basic material on my objects Oo,

and i thought that when choosing full irradiance it will compose the AO and the beauty pass automatically and i can't see the AO effect on my image

in fact the only difference between the AO and Full irradiance modes is the color bleeding ( and in both in don't seem to get the AO working un less with a basic white material)

what i want is an image having the AO integrated automatically without rendering 2 passes and passing in cops to do the comp , is it possible? can someone please explain the modes in the vex GI node in little detail ?

Thanks in advance

Best Regards

Edited April 3, 2009 by nmn

[SpencerL]

Hi everyone,

the question is can we obtain an image with the beauty pass and AO pass composited directly out of 1 render (without passing through cops? )

in fact at first i thought it was straightforward, using the vex global illuminatin on a light template, but either i'm doing smtg wrong here or there is smtg i didn't really understand.

when we use the vex GI node with it set to ambient occlusion i see no AO, unless i use like a white basic material on my objects Oo,

and i thought that when choosing full irradiance it will compose the AO and the beauty pass automatically and i can't see the AO effect on my image

in fact the only difference between the AO and Full irradiance modes is the color bleeding ( and in both in don't seem to get the AO working un less with a basic white material)

what i want is an image having the AO integrated automatically without rendering 2 passes and passing in cops to do the comp , is it possible? can someone please explain the modes in the vex GI node in little detail ?

Thanks in advance

Best Regards

You dont need to do all that vex GI stuff....You can add Occlusion in your surface shader. Check out the Occlusion and/or Irradiance VOP.

[nmn]

thanks for the tip SpencerL, it was helpfull,

isn't there a way to apply global AO, without doing it inside every shader (of course with the same conditions in my first text ) ...

Regards

[sibarrick]

You can add it to your light shader. There's an example over on my website HoudiniTools.com

[nmn]

thanks sibarrick, (Y) nice works on your website

isn't that possible with default houdini ? without installing your otl ?

and any explanation about the VEX GI node modes would be really appreciated coz it's not functioning as i expect it to do :S

in fact my tests showed that if in irradiance mode there is no AO taking place, is that correct or is there smtg i'm not getting right ?

Thanks

Edited April 4, 2009 by nmn

[DaJuice]

Not sure what's wrong nmn, it's working as expected here (aside from immense slow-down when switching to Full Irradiance )

vex_gilight_occlusion.zip

[nmn]

in fact what's bothering me is the following :

i have a scene consisting of a floor, and a cube on it

- setup one : constant shader on the cube (with occlusion multiplied in the vex network), basic shader on the floor (with irradiance added and occlusion multiplied by the irradiance result in the vex network )

- setup two : constant shader on the cube, basic shader on the floor, light template with vex_gi attached to it and set to full irradiance

both cases no other lights in the scene, and my constant shaders are there to act as light emitters

and the results are different while they have to be the same Oo, in fact in the setup with full irradiance i can't seem to see the AO :S

i know the constant shader in houdini doesn't receive neither AO nor irradiance, but i'm talking about the floor no AO with full irradiance

i assume they add the GI after calculating the AO :| , so it just covers it Oo ?! coz in fact AO has to be multiplied by the GI result then added to the diffuse

in your scene it's there though, maybe because you don't have some light emitters to cover it ?

you're confirming that full irradinace = GI + AO ?

Regards

Edited April 4, 2009 by nmn

[DaJuice]

An emitting object on a floor is not the most ideal scene for testing AO.

- setup one : constant shader on the cube (with occlusion multiplied in the vex network), basic shader on the floor (with irradiance added and occlusion multiplied by the irradiance result in the vex network )

Full Irradiance already includes the AO. It basically adds a diffuse bounce to direct lights and occlusion (hence color bleeding).

Edited April 4, 2009 by DaJuice

[nmn]

you're right DaJuice this problem seems only to appear in the scene where there are the object light emitters,

but what's confusing me (maybe always because of my maya background) is that AO is shader independant (at least in MR)

and that in my vex networks where i added myself the AO and ireadiance (i added them in a way that will calculate them like in maya ) it's giving a different result than with the full irradiance that in this case is taking AO all the way out

Cheers

Edited April 4, 2009 by nmn

[DaJuice]

you're right DaJuice this problem seems only to appear in the scene where there are the object light emitters,

but what's confusing me (maybe always because of my maya background) is that AO is shader independant (at least in MR)

and that in my vex networks where i added myself the AO and ireadiance (i added them in a way that will calculate them like in maya ) it's giving a different result than with the full irradiance that in this case is taking AO all the way out

Cheers

Your two setups will have different results, because in setup 1 you are doing redundant calculation by multiplying full irradiance and ambient occlusion in vex (remember full irradiance is already handling AO).

[nmn]

Your two setups will have different results, because in setup 1 you are doing redundant calculation by multiplying full irradiance and ambient occlusion in vex (remember full irradiance is already handling AO).

Ah no i think you got me wrong, in fact in setup one what i did was adding the irradiance node inside my vex network. or you wanted to say that this same irradiance node also handles the AO ?

Edited April 4, 2009 by nmn

[DaJuice]

or you wanted to say that this same irradiance node also handles the AO ?

Yes. The background color in the irradiance vop will give you AO. As for the best way to use irradiance inside a shader, I'm not sure. At most I've used occlusion vop to output an AO pass.

[nmn]

thanks for the clarifications DaJuice, i guess i'll be doing some more tests on the matter

[rob]

Hi ,

Render your scene using the gi_vex light , when you look in your export nodes in your renders.The diffuse export has the diff with the irradiance or you can use the occlusion VOP to build a shader and export out a pure occlusion pass. This of course will need multiplying in comp with your diffuse and paint passes.

Or you could render your occlusion , build a shader and read in via a texture VOP the pure occlusion pass the mult it inside your Vop shader. I guess that would be better for actually controlling your environment light contribution while getting faster render feed back.

I would also make sure you render all your AOV's ( image planes with an Alpha) using the minmax edge filter. If you are using anything other than Nuke to comp. Shake has a painful problem where .exr's get loaded in with flipped channels.

r