Show base material in the VRayMtlWrapper ?

[bigbossfr]

Hi,
Here a little problem that i can't solve.
I have a ground, i do a camera mapping on the ground.
I want the ground have a "matte surface" (like a surface shader), but, i want shadows on my ground, and see the ground.
How can i do this ?

[chuckie7413]

I am having the same issue.

I was shown how to do this by Konstantin at FMX and it looked as though it was possible but I have had trouble recreating it.

Look forward to hearing an answer.

Many thanks,

Richard

[chuckie7413]

Any info on this?

Cheers,

Rich

[Zdravko]

Here is an example scene of a matte surface with shadows.
If you don't want GI on the matte surface you can turn off (receive GI) form the material properties.


Also what do you mean by:

I want the ground have a "matte surface" (like a surface shader), but, i want shadows on my ground, and see the ground.

[chuckie7413]

Hi Zdravko,

For me (which I think is the same as bigbossfr) is that if we are rendering a cg object into a photographic backplate, I want the object to pick up correct reflections from the ground of the backplate. (Not the 360 hdr because might have been shot in slightly the wrong position or be missing details that have been comped into the backplate image) To do this I would project the backplate onto geometry representing the ground. Now the backplate already has all the lighting information in the image. Therefore it should not recieve any light. But by plugging the image into the diffuse component of a vrayMtl, it will not output the same colour values it has in it as it is relying on cg lights to light the texture. So the resulting reflection of this groundplane could be too dark or too light.

What we want is to be able to plug a vrayLightMtl into the base material so the ground plane keeps it lighting information. Then the shadow of the cg object is computed and masks the corresponding areas of the groundplane image so it is picked up in the reflections correctly.

Does this make sense?

Cheers,

Rich

[Yannick]

I would like this as well.
thanks

[Zdravko]

We are not sure if that is the same effect but still, try the following:
You just need to set your HDRI (or environment image) in the Reflection slot of the Environment slots in the VRay tab. Set your projection texture in a environment slot of a material override added to the shading group of the VRayWrapperMtl.
Also make sure you have Matte for secondary option option turned on in the VRayWrapperMtl.
We attached another scene for comprising.
Instead of 2 images we used 2 ramp textures one with spherical textures and one with screen mapping.

[RobPhoboS]

I've got some lessons to finish off first before diving into more Vray BUT does this post also contribute to similar issues you guys are having ?
http://www.chaosgroup.com/forums/vbu...nd-reflections

I will do some testing next week but I've not seen any other reports of issues when matchmoving with live action & CG.

[chuckie7413]

Hi Zdravko,

This looks more promising but I opened your file and replaced the ramps with an actual backplate image and hdr and if you look at the render you notice that the reflection onto the sphere not correct. It seems as if the reflection is mapped onto the sphere in screen space. I suppose the VrayPlaceEnvTex is set to Screen Mapping so this might explain it, however on your render the reflection onto the sphere of the ground looks correct. Maybe I have missed something when swapping in the images.

Can I email you my scene. (Can't share these plates and hdr on forum without asking permission)

Thanks,

Rich



p.s. ignore the attached thumbnail. upload error issue

[Zdravko]

Yes, feel free to send us the scene to vraymaya@chaosgroup.com

[Zdravko]

We missed to make a projection from the camera. Here is the scene again.
Also soon this setup will be supported by the RT as well.

[chuckie7413]

Hey Zdravko.

Yeah this is what I thought was missing. The one issue is that you can see where the projection wraps.



I changed the UV behaviour of the projection texture so it does not wrap in U or V and then plugged in the hdr reflection image into the Default colour of both the projection file and the projection node itself so the ground then picks up the environment texture in this area.



This seems to be an acceptable solution.

However I would like a bit of help understanding how exactly this is all working?

I do not understand how the environment overide attribute on the wrapper material works. My understanding of an environment overide is that the objects material will now reflect the image plugged into it. However the material itself is not reflective? Or is this what the Matte for all secondary rays option does?

Thanks,

Rich

[Zdravko]

Konstantin will send you an e-mail about that.

[snivlem]

Here is an example scene of a matte surface with shadows.
If you don't want GI on the matte surface you can turn off (receive GI) form the material properties.

Hi there, sorry old thread - but how does one use this when using physical sun + sky?

It seems to be really noisy and shadows pure black?

[vlado]

Are you using a dome light or just the sky in the environment maps?

Best regards,
Vlado