Plate Material

[Dave_Wortley]

When Rendering a car for integration with a background plate we use the HDRI from the shoot to light the scene and the HDRI for reflections. We then take our plate and use it as a 100% self illuminated map, or VrayLightMtl. The only problem then comes that we can't get shadows from the car to cast on our plate so the shadows are reflected into the car. We have to do it in 2 passes first to render out just the shadow comp this with our plate then use an animated sequence to get the shadow reflected in the carpaint.

What we need is a material that is 100% self illuminated but can still receive shadows

Apparently there's a way to do it in Maya, but our ex-maya guy can't remember how...

[MoonDoggie]

This seems like a bit of a strange request, you want shadows on a bg plate? The shadow on a plane would look very strange at any rate. I guess I'm not understanding correctly.

[super gnu]

you might be able to do something with a falloff map set to shadow/light? masking between materials with different brightnesses?

[Dave_Wortley]

This seems like a bit of a strange request, you want shadows on a bg plate? The shadow on a plane would look very strange at any rate. I guess I'm not understanding correctly.

We use the plate projected on a modelled 3d floor so the car reflects the surface of the road, we need it to reflect the shadows the car casts on this 3d floor....

We would normally render off a seperate shadow pass for the car and comp this on the plate, but just seems a bit of an unneeded overhead to bake our shadow into the plate first.

[simmsimaging]

I feel your pain on this one. We really need a simple "shadow catcher" material for Vray, then you could just layer a new plane just over the background to just receive the shadows. I think modo has a good implementation of this.

[MoonDoggie]

That's what a mtlwrapper is for set to "matte surface" and "shadows"? Surely I'm missing something.

[simmsimaging]

Doesn't that just give you a shadow element though?

[MoonDoggie]

One sec, I'll test.

[MoonDoggie]

Yeah, couldn't figure it out.

[simmsimaging]

I've tried many times, but really: if the guys at TJ can't do it, I'm pretty sure it's not getting done

I also looked at the mtlwrapper today, but it seems that it just provides a material level control of the normal vray matte object properties, and those don't give you a "shadow catcher" in the way I meant.

/b

[anchovy]

Yep all the places Ive workd at weve comped a shadow pass into the plate and then reprojected for reflections. A pain but it gives you what you need.

-Michael

[AJ Jefferies]

I've done this in the past by duplicating the floor plane/objects you want to have shadows & shifting them down a tiny amount, then select the original version (in the 'correct' place for the shadows), apply a plain vraymat & then under the vray properties making it a matte object & ticking shadows.

That's off the top of my head, so there might be a little bit more to it than that. It's dirty, but it works

[joconnell]

An even dumber approach is to light the shot and make the ground object a normal, non illuminated material and then light it enough until the values of it matches the rest of the backplate. dumb and incorrect but you get your shadow.