How to get Shadow without Reflection?

[breadcrums]

Hi everyone, I have a question that should be simple but is driving me crazy...

In this basic example I am rendering a chrome teapot.

With no ground plane, the teapot looks like it is floating.


With a ground plane with a basic material applied to it, the teapot is grounded with a shadow and also the reflection of the plane.


With a shadow material applied to the material, the shadow renders correctly in the alpha channel BUT there is still a reflection in the teapot (Here I made the base material green to better illustrate)


I turn off reflections in the Object properties of the plane and I lose the reflection but ALSO my shadow

How do I get a shadow reflecting back into my teapot, with out seeing the friggin shadow plane itself in my teapot?

I am using a Vray Material as my base material in my shadow material, since that is now a vray 3 thing apparently.
in my vraymtlwrapper I set the alpha contribution to -1, shadows and affect alpha are ON, Matte surface is ON.

[kosso_olli]

This has been bugging me for years... Still don't have a solution for it. There is an option called "matte for refl/refr", but most of the time it does more harm then good...

[Rens]

Matte for refl/refr seems to work fine for this. What are the problems you're having with it?

[kosso_olli]

Please take a look at the attached image. If I light the scene with an HDRI, the HDRI somehow gets mapped onto the plane the shadow is cast on. This leaves a visible distortion at the horizon in the reflection. You can clearly see a hard edge there.

[breadcrums]

Matte for refl in the material properties? This just blacks out the entire reflection of the plane. I don't want to see the plane at all! Just its shadow

[breadcrums]

Even Keyshot has this ability. I'm really surprised there isn't a work around in Vray?... I would think literally everyone using hdris in Vray would run into this problem?

[kosso_olli]

I am wondering why something so simple is not available in Vray yet, too.

[Dariusz Makowski (Dadal)]

What version of vray are you using? I know this has been asked before and there is working solution.

[breadcrums]

Latest and greatest- 3.00.08

[Svetlozar Draganov]

You can get the shadows only with the help of Falloff texture(Light/Shadow mode) applied into opacity slot of the BaseMTL.
This however is going to work only with direct lights like sun for example, it won't work for area lights like plane/sphere and etc.


Scene: http://ftp.chaosgroup.com/support/matte.max

[breadcrums]

oh nice, I played with opacity maps in the base material but couldn't get satisfactory results but I also use hdrls almost exclusively so I was trying with a dome light. The opacity map didn't help until it bled into the shadow itself, otherwise you still saw the plane. its like i need an opacity map that is the baked shadow o.0

[kosso_olli]

This however is going to work only with direct lights like sun for example, it won't work for area lights like plane/sphere and etc.

Sad to hear that. This feature would be most usefull together with a domelight, for example. Also, how does this work with GI?

[Svetlozar Draganov]

A better workaround would be to bake the shadows and use that texture as opacity map instead Falloff texture.
The downside here is that you have to update the baked shadow map each time when the light-setup is changed.

[Rick Eloy]

I might have misunderstood the question, but doesn't the Visible to Reflection/Refraction option in the Object Properties do just that?

[breadcrums]

No, turning off visible in reflections kills the shadow as well. I want JUST the reflection of the shadow not the reflection of the shadow plane.