ground geometry that catch shadow and return projected plate color without affected by scene lighting

[jasonhuang1115]

Hi all,

I have been trying to achieve this in Vray but couldn't. In Arnold, I can achieve this by assigning an aiShadowMatte shader to a ground geometry. In the aiShadowMatte, specify using "background color" and plug a projected plate image. In a single render, I got a ground that returns projected plate color, which is not affected by scene lighting, and the shadows. (example below)


In Vray, I've tried assigning VrayMtlWrapper to the ground geometry. But as I use a VrayLightMtl with a projected plate as the Base Material, it cannot catch the shadow. And as I turn on Matte Surface (Alpha Contribution -1, Shadows On, Affect Alpah On), the shadow is in the alpha channel but not in RGB. Also, the whole ground is black, which is the environment color.



Will be happy to learn a way, either object property-based or shader-based setup to achieve this in Vray.
If this is not achievable, please consider this as a feature request. I'll be more than happy to add a thread in the Wishlist subforum.

To John O, if you came across this thread, I really don't want to bake the lighting. It works, but I can't then change scene lighting without re-bake.


cheers,
Jason

[kosso_olli]

With the V-Ray Toolbar, creat a Vray_Plane under the box, and use the "make V-Ray shadow catcher"-button from the toolbar while plane is selected. This takes care of evereything, you don't need to do anything else.

[jasonhuang1115]

Hey kosso, how is your Vray_Plane textured in this scenario? Meaning, are you assigning any texture to the Vray_Plane?
I used a simple plane to explain the issue. But actually, the idea is to have a modeled geometry of a more complex shape with a texture assigned to serve as the shadow catcher while being able to return the texture's original color except for the shadowing effect.

[kosso_olli]

The Vray_Plane is not textured at all, it has a plain gray Vray-Material. The shadow catcher gets is texture by the projection of the map in the environment or secondary matte environment slot.

[jasonhuang1115]

The Vray_Plane is not textured at all, it has a plain gray Vray-Material. The shadow catcher gets is texture by the projection of the map in the environment or secondary matte environment slot.

Right, kosso, and that's exactly why I can't get the result I expect. I want the camera rays to return the texture information of the set geometries, not from Vray Plane or any environment slot.