Ambiant Occlusion with sand and procedural


That’s my first post (haven’t found presentation thread).

I’m a Blender newbie (using it for a month) and I have trouble with Ambiant Occlusion ; Basically I would the walls of my scene to be a bit dirty on the connexion of the sand so I use ambiant occlusion.

I’m trying it on the scene below (blue to highlight it now, will change color later) but the gradient with the sand is very large when it’s very small (as I want) on the sphere and wall corner.

Do you know why and how can I solve that issue ?

The sand of the room is a plane with procedural texture, may be linked ?

Nishita world.

Scene with good AO / Same scene with the sand in render :

Texture of the Wall (AO part) :

Thank you !!

Hi and welcome.
First try to change the ‘Distance’ parameter in AO node to check if this can solve the problem.
If not, you can post the .blend file here. It will be easier to troubleshoot.
Oh, and it is Ambi-E-nt Occlusion.

Before posting blend file here be sure to pack all textures into .blend file: “File” → “External Data” → “Pack resources”. This will include all your bitmaps and textures inside the .blend file.

Thank you for your help ! I tried a .2 on the distance and this is working well except that AO behave differently between the sand junction and the sphere/wall junction. Any clue on that ?

Also, closer you come to the junction darker it should become, and here is not the case between sand and wall.

I have packed all my blend file here (this is my learning file … )

Same scene with a .2 on the AO :

Oh, and from I’m coming from, on dit occlusion ambiante :smiley:

Wait, to clarify, you want the AO to be on the sand as well? Is that what you want?
Like that:

The AO on the wall is behaving quite normal and you did a good job on that part.

But if you mean about different amount of AO falloff ‘shadow’ generated in two places - that pretty much depend on the geometry itself. That includes the shapes itself and the sizes of the meshes. AO falloff is calculated automatically and there is not much you can do aside from playing with Distance parameter, or plugging into it modes that can drive it.

However there are ways to control AO around the sphere and AO around the sand separately, but they are not very straightforward nor they are identical.

Nope, I think I wasn’t clear but I don’t want AO on the sand, don’t really make sense for the scene I think.

What I don’t understand is why the AO is so different between 1 and 2 on my render when it looks almost the same on your…

Can you also share with me the parameters you used for the color ramp on the wall ? It takes me ages to adjust with my super slow computer…

Thank you again :slight_smile:

Well the AO will always be more pronounce in places with a lot concave geometry - like the area between the sphere and the angled front wall. That pretty much won’t change no matter the settings, as I wrote there are ways to overcome this with mixing two AO with different values, but that involves creating masks between different parts of the geometry.

AO do not detects mesh intersections, but closest point (kind of) to other parts of the mesh/meshes. That’s why the area between the sphere and angled wall is ‘darker’.
See this for example:

Here are the settings:

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Thank you, you helped me a lot :wink:

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