VRay Ground Plane + Shadows? HDRi

[gantonski]

So, i'm familiar with the matte shadow technique used in 3DS Max, where you can use a backplate and have an invisible ground plane but still cast shadows on the background.

i saw this one video where this guy put an SUV into a warehouse and used a radial gradient transparency map to create that affect. i'm trying to recreate it and its a terrible trade off i cant overcome.

I can have the ground plane invisible, and receive shadows, and align with the background...... but at the cost of the horizon line having a hard brightness transition from ground plane to background materials. OR, i can have the background look normal but the ground plane receives no shadows.

I'm using environment mapping for background
I'm using an HDRi GI map for lighting.
I'm using VRay Infinite Plane for the ground.

I've attached two copies of the problems i've just described, each with different backgrounds.


Please note that for this particular problem i do not want to add any (matte)shadows in post. I want the ground plane to be invisible, but receive shadows, directly from the VFB.
also, i've checked the forums and found some stuff but i'd like to have my own discussion so that i can be more clear about the answers.

The images are attached below. Thanks!

[fpedrogo]

Hi
The mapping for the infinite plane is a little bit different than a regular surface. So instead of the infinite plane, you should use a regular surface to get the correct mapping and in this case you could match the HDRI image in the Environment with the HDRI in the ground material. This is an old workflow in V-Ray 1.05.29 to fake matte shadows.
In V-Ray 1.5 we add the V-Ray wrapper material, which is the material to create matte shadow. So. in the new build you can use the same workflow as in 3ds Max.

Fernando

[gantonski]

fernando, you're amazing. I'll give it a shot today.

I did read about the the wrapper in the nightly build, but unfortunately i dont have a commercial license. Do you know when that build will be released?

Thanks, fernando!

[fpedrogo]

Unfortunately, I don't know when we are going to release a new build.

Best

[kostenurka]

Personally I can't benefit from using the V-Ray wrapper material. It works only in particular conditions.
I spent lots of hours on it..but matte shadow effect is super anemic as long as dome light feature exists in the scene

To me the most difficult thing for post working my renders are the shadows! these are very sensitive areas especially the borers and transparency which should perform great on any set color layer underneath after!!
It is sad we can't benefit from such feature yet! Hope someone make a tutorial at the moment nightlie built allows it.

[fpedrogo]

Hi Kostenurka
If you are using dome light, you will have to place the same HDRI or the image that you want as a background on the environment reflection/refraction(background).

[Micha_cg]

My favourit method to get transparency shadow is:

* use a simple groundplane material, but disable double sided and render it from the bottom view
* create shadow texture from this render and apply it to the ground
* for the ground use a black material and use the created shadow texture for transparency, so the shadows are colored too.
* the final transparent shadows are dependent from the used background color, black will cause a deeper shadow effect

So I got perfect transparent shadows. The shadow texture can easy fine adjusted at PS. This process is done within a few minutes and help to get grat shadows.

[Micha_cg]

So, i'm familiar with the matte shadow technique used in 3DS Max, where you can use a backplate and have an invisible ground plane but still cast shadows on the background.

Fernando, is using a backplate possible per VfR? I tried it, setup a screen mapped ground material, but the wrapper material doesn't show the screen mapped ground. Did I have something overseen? Or is a some additional code refinement needed?

[kostenurka]

Hi Kostenurka
If you are using dome light, you will have to place the same HDRI or the image that you want as a background on the environment reflection/refraction(background).

fpedrogo,
it still does not work. See the attached image. What I marked as unwanted overlay is what dome light produces (also when set to invisible). This overlay it makes impossible to benefit of what should Wrapper material produce!
The settings are:
alpha contribution of Wrapper material is -1
dome light is set to invisible
same HDRI for both dome and environment reflection/refraction

Now, should I report this as a bug, although I'm sure this issues is not new to chaosgroup? This is probably the 15th nightlie built since problem is known and nothing has been improved.

[fpedrogo]

Hi Guys
First, I want to mention that this is not an official Chaos Group video. It is a personal video that I did in my free time for you, but i thought it will be easy for me make a video with the wrapper material explanation. So, the resolution and the audio is not perfect. Having said that, here is the video and I hope you can enjoy it.

http://www.youtube.com/watch?v=tKS9U93HvTM

Fernando

[Micha]

Great, thank you for the informative video. Before I tried to get the screen mapping working for a wrapper material, but don't got it - but now I understand.

[fooprobe]

nice video fernando, thanks for that!

[renee81]

Thank You!

very much appreciated,

[gantonski]

this is only for the nightly build, right? Which education licenses do not have access too, right? So, unfortunately i'm still stuck!! But, once the build is released i will be forever grateful!!

Thanks, fernando!

[Svetlozar Draganov]

Unfortunately only ADV-users have access to Nightly-Builds, so the only option would be to wait until official release.