OnlyShadow and Ambient Occlusion problem

Hey everyone

I’m trying to work out the best way to make an object cast a shadow in an entirely white surrounding with no visible floor.

I’ve worked out that if you add a plane for the ground and set it’s material to only shadow and turn on Ztransp it’s easily done. However, I also want to use AO as well which unfortunately seems to almost wash out the shadow until it’s only just visible when it’s turned on.

How can i achieve a strong shadow whilst using Ambient Occlusion at the same time?

AO is set to Add by default (in the AOPanel) and making everything brighter.
Using Sub instead or Both together with Energy you can vary this getting things darker.
For further corrections you could use nodes with an extra AO Pass and combining it how you like.


If you are happy with how AO looks on the other objects, just turn down the AMB setting (on the Shaders tab) for the Plane material. AMB controls how much AO effects the material.

Thanks Patel and DichotomyMatt for your advice.

I’m actually happy with how the ambient occlusion looks on the actual model using the ‘add’ setting so i don’t want to change if i can avoid it. It’s just the shadow being cast on the invisible floor that’s the problem.

Lowering the Amb setting for the material for the floor had the reverse affect of what i expected to happen. It made the shadow even weaker. However making the Amb setting higher did help to strengthen the shadow. Oddly though, considering that lowering the setting made the shadow weaker, a setting of 0 made the shadow very dark and strong as if it were not affected by AO at all.

Also i found i needed to increase the ‘max distance’ for the AO settings as well as lower the ‘falloff strength’ to get more shadow to appear.

Still feels like i don’t have total control of how I’d like the shadow to appear but it has improved, so thanks for the help.

If the shadow appears too dark, lower the alpha value on the material (the A slider). When you have only Shadow selected the Alpha value will make the shadow more or less transparent.

If i set the ‘Amb’ to 0 then yes the shadow is too dark as it is not being affected by AO at all. So… lowering the alpha value will make it more transparent, only it looks a little unnatarual to my eyes without a little AO affecting it to soften it in places.

The closet i’ve got to achieving my goal is setting the ‘Amb’ as high as it will go to 1, but the shadow is still a bit weak. I guess this means adjusting the AO or lighting settings only that will change how the model looks as well, which i’m pretty happy with.

It’s not far off how i want it though… so thanks again for the help

There’s also a good tutorial in BlederArt Magazine 15 about rendering to showcase a product.

As an alternative add the AO in post pro using compositor in blender. Use RGB curve to tune it’s color.