Shadow Catcher

[vandigital]

How does one do this in vray for modo?

[vmodo]

Same principle like with MODO Renderer. Additionally you have to enable the V-Ray Object Properties in the Shader-Item and setup
the Matte Properties according to your demands.
http://docs.chaosgroup.com/display/V...ect+Properties

[Dentzz]

How does one do this in vray for modo?

I am not sure that all of these steps are correct but if no one else writes here maybe it will help get you in a further correct direction. Apply a shader on a material like you normally would in modo bringing it above the base shader. Make sure the base shader has a vray object property on it. In the vray object property make sure it is enabled as this gives you the matte properties.

If you have environment importance sampling off setting alpha contribution to -1 should give you a shadow catcher and alpha on the shadow. With Environment importance sampling on, and this is where I think I don't know if I am doing something wrong or vray is. To get it to at least appear to work I have to set GI amount to 0 or Received GI to 0 which I am pretty sure is wrong.

[Margarita.Stoeva]

Hello!

What Dentzz said is correct. You need to create a new shader and place it in the material group that you'll use for the Shadow catcher. Enable the V-Ray Object properties for this new shader and in its Matte properties enable Matte Surface and set the Alpha contribution to -1. Then drag the whole group above the Base shader. This only works with EIS disabled (not working with EIS enabled is a known bug).

Best regards,
Margarita

[vandigital]

Ah thanks for that info hopefully that will be something that is automatic in the future when you select shadow catcher in the shader layer.

Do you know if that bug has been fixed in the nightly's Margarita?

[vmodo]

Speaking of "...further correct direction"
Dentzz, Vandigital released about 6 years ago "Rendering Techniques for MODO 401" it was than the most comprehensive Explanation of the inner working of the MODO Renderer - I am quite sure that he knows how to setup the Shadow Catcher in MODO, hence my "Same principle like with MODO Renderer."

[Margarita.Stoeva]

Do you know if that bug has been fixed in the nightly's Margarita?

It hasn't been fixed yet. I added a fresh note in our bug tracking system.

[vladimir.nedev]

The "Shadow catcher" option of the "Alpha Type" drop-down in the Shader item should work with V-Ray for MODO. You don't really need the V-Ray Object Properties, unless you need some of their specific options.
I usually add the ShadowCatcher preset from Meshes -> Basic from the default MODO presets.

The problem is with the "Environment importance sampling" option. In this case the created Dome light will be reflected by the shadow catcher (so you can basically see where the shadow catcher plane ends).
I fixed this case when EIS is off, but not when it is on. I am not sure how this is done in V-Ray for 3ds Max/Maya. Maybe you are supposed to exclude the environment Dome light from affecting the shadow catching plane.

Greetings,
Vladimir Nedev

[SonK]

Would it be possible to make shadow catcher work on VRay RT CUDA? Currently it does not.

[vlado]

Would it be possible to make shadow catcher work on VRay RT CUDA? Currently it does not.

The GPU guys are currently looking into it.

Best regards,
Vlado