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Ambient Occlusion on a Standard Material
show user profile  cartwright_mj
I just watched this tutoria
at 2:30ish, the Ambient Occlusion is attached to the diffuse box but what is my diffuse box already has a bitmap (wood floor in my case) already there??
read 492 times
2/18/2015 1:51:14 PM (last edit: 2/18/2015 1:51:14 PM)
show user profile  mike_renouf
I think you could create a composite map and put that into the diffuse slot. Then within the composite map put the wood floor texture as one layer, and the AO pass in another slot (probably set the AO pass layer to multiply).

read 489 times
2/18/2015 1:53:13 PM (last edit: 2/18/2015 1:53:13 PM)
show user profile  Mr_Stabby
Better yet, use A&D material and its built in AO. Mixing AO into other maps can be tricky to achieve a realistic result since the regular AO map is not physically anchored, nor is it capable of retrieving the occluding environment color

read 481 times
2/18/2015 2:37:27 PM (last edit: 2/18/2015 2:37:27 PM)
show user profile  cartwright_mj
It doesnt seem to work that way Mr_Stabby

read 470 times
2/18/2015 3:29:15 PM (last edit: 2/18/2015 3:29:15 PM)
show user profile  BishBashRoss
Best to do it as a pass and then apply in post really.

read 465 times
2/18/2015 3:32:50 PM (last edit: 2/18/2015 3:32:50 PM)
show user profile  cartwright_mj
Id really like this to work without post as I will animate the scene as a flythrough. I can't understand why the above image doesnt work??
read 460 times
2/18/2015 3:41:38 PM (last edit: 2/18/2015 3:41:38 PM)
show user profile  Mr_Stabby
Probably because there is no light qualified as ambient hitting the surface. Ambient light can be produced indirectly(physically correct) by photons or fg or directly from environment constant or lights with ambient only checked.

heres a sample of fg ambient light being occluded

read 456 times
2/18/2015 4:12:49 PM (last edit: 2/18/2015 4:13:59 PM)
show user profile  cartwright_mj
My teapot is behaving correctly????
read 448 times
2/18/2015 4:22:26 PM (last edit: 2/18/2015 4:22:26 PM)
show user profile  FX
If your animating your scene do it in post as a separate pass, it's the only way you'll get good AO results.

your not rendering to .avi are you ?

read 445 times
2/18/2015 4:25:06 PM (last edit: 2/18/2015 4:25:06 PM)
show user profile  cartwright_mj
No, separate jpgs then into Adobe premiere
read 442 times
2/18/2015 4:27:04 PM (last edit: 2/18/2015 4:27:04 PM)
show user profile  FX
then render your AO as a pass and comp it.

edit: ahh...mental ray


read 440 times
2/18/2015 4:29:12 PM (last edit: 2/18/2015 4:32:29 PM)
show user profile  cartwright_mj
OK, a little background. for the quality I need, I model/colour/texture my scene then add an omni light and enable the light shader ( I choose Ambient/reflective Occlusion). I render in MR with no final gather and the result if a pretty OK image with an effective AO (time/look wise).
However, this applies AO to the whole scene but there are parts of the scene that I could get away with this not being applied to. I thought the result would be to ditch the omni light and give only the material I need to be AO the relevant material ( I would also have much more control over the samples/ max distance etc) . So, I find myself in this position, I need to apply AO to certain material and not others. I dont want to do a pass that if global as I kinda already do that. Any advice??
read 433 times
2/18/2015 4:53:00 PM (last edit: 2/18/2015 4:53:00 PM)
show user profile  FX
Just exclude what you don't want including in the pass...I use Vray so not qualified to help.
read 430 times
2/18/2015 4:56:58 PM (last edit: 2/18/2015 4:56:58 PM)
show user profile  mike_renouf
I think the problem you have shown in your screenshots is that the AO distance for the floor material is set to 2000. If you're working even in scale of millimetres this means that the darks and lights of the AO are set to be spread across a full distance of 2 metres - i.e. far away from the teapot. YOu're basically not seeing the AO because its too far spread.

Try dropping the distance down to a shorter distance like 50 millimetres.

read 409 times
2/18/2015 6:17:33 PM (last edit: 2/18/2015 6:17:33 PM)
show user profile  cartwright_mj
Are you sure? As far a i was aware, the 'higher' the number the 'darker' the image would be. Yes it will spread to 2 metres but as long as the darks are on black, it won't 'spread' the shadows more thinly
read 404 times
2/18/2015 6:22:55 PM (last edit: 2/18/2015 6:22:55 PM)
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