Ambient Occlusion

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1

Hallo

I am having trouble doing an ambient occlusion render of an interior. I can only get an all black render. Should I take out the glass or an unseen wall? I have tried increasing the environment etc, any help or ideas would be most welcome. Or is it unecessary?

I am using vray 4 sketchup 1.49.01 and windows xp with sketchup 8

2

Re: Ambient Occlusion

Hi
To make a AO pass for interior render, you need to use Dirt inside an emissive material. These are the steps

For the AO material

1. Make a new material
2. rename that material with “vrayoverridematerial” - this is the internal name that we use for the override material on the “Global switches”
Basically you can use any material as your override material if the name of the material is “vrayoverridematerial”
3. Add an emissive layer.
4. Apply the “Dirt” on the emissive color mapping slot.
5. Click on the ‘m’ near “black” and selec “Acolor” and apply a black color ( or the color that you want to use as your AO color). If you don’t use an “Acolor” the dirt doesn’t look good.
6. Change the radius to 15 (or your desired value) - This determine the area in which you are going to have AO. Larger number more area with AO.
7. Increase the subdivision of the dirt material. I use 50 on my example.
8. Go to the "Global Switches and enable “Override Material” option.
9. Disable the Light option and the shadow on the “Global Switches” to exclude these components from the AO.
10. Disable any mapping on the “BG Color”
11. Click render.
12. Save the image as a png to remove the black background

3

Re: Ambient Occlusion

Many thanks I shall try it

4

Re: Ambient Occlusion

There does have to be an opening to let light into your interior. AO will not work without some GI light getting in. You can put your glass on a layer and turn that layer off.

5

Re: Ambient Occlusion

There does have to be an opening to let light into your interior. AO will not work without some GI light getting in. You can put your glass on a layer and turn that layer off.
You don’t need to do that. The emissive material is going to produce the necessary light top get AO even in a close interior.

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Re: Ambient Occlusion

AOnmnoglass
AOnmnoglass1024×768 70.7 KB

Have done a quick test with glass in the room and adjacent room removed. Have used a radius of 20 on the emissive colour with sub divisions of 50. The colour was nearly black. Hopefully thats of use to someone!

7

Re: Ambient Occlusion

oh - learn something new every day. I didn’t notice the emissive part. Thanks Fernando.

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Re: Ambient Occlusion

I thing you have to increase the intensity of the emissive material. The unoccluded area should be 100% white.

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Re: Ambient Occlusion

This is my test with the emissive material method. I Also disable the GI on the indirect illumination.

Radius = 10
Subdivs = 80
Emissive multiplier = 5

Best