Matte Shadows/Reflections (Warning: Kinda long post)

[danimation3d]

I do a lot of jobs where I need to place 3D models into real photos, in a very realistic fashion. (Check www.virtualfurniture.com.au if you're unsure of what I'm talking about )
This means there are shadows on the walls and floors where objects make contact, and reflections where necessary, eg. polished floorboards showing the reflection of a dining table.

Currently, I do this with Mental Ray, using the Matte/Shadow/Reflection materials and a scene setup technique I've worked out. I've explained my current Mental Ray workflow below.

Now, I'd like to do the exact same thing, but with VRay.
But I just need some help with setting up the material to catch shadows and reflections, and some form of indirect lighting for soft shadows (if possible).

Notes:
-The floors/walls must NOT show weird shadows or black lines around the edges
-I'd rather use some form of indirect lighting for soft shadows, rather than a direct light (as per my Mental Ray scene using Skylight)
-I'd like to stay away from using Render Elements if possible. I want to be able to do test renders inside 3DS, and see good results, rather than having to layer everything in Photoshop, just to find something is wrong.
-Reflective floors are a MUST


My setup:

Materials Setup
-Import photo bitmap to Material Editor, set as Texture (Explicit Map Channel)
-Duplicate bitmap, set as Environ (Screen)
-Create maps “Camera Map Per Pixel”, “Matte/Shadow/Reflection” x2, and “Environment/Background Switcher”
-Plug bitmap (Explicit) into both “Camera Map Per Pixel” texture slots
-Plug “Camera Map Per Pixel” into each of the “Matte/Shadow/Reflection” materials, in the Camera Mapped Background slots (one is for walls with no reflections, one is for reflective floors)
-Rename Matte/Shadow/Reflection materials to Floor and Walls. Set Floor to Receive Reflections
-Plug bitmap (Screen) into “Environment/Background Switcher” in background slot
-In “Camera Map Per Pixel”, select camera

Scene Setup
-Import photo as background
-Set render output to match photo, lock Image Aspect, and scale down to speed up test renders
-Turn on Mental Ray renderer
-Perspective match photo
-Create camera from current view
-Create Skylight from standard light menu (IMPORTANT: I use the skylight, because it creates soft shadows. No directional lights. A similar workflow in VRay would be much preferred)
-Make sure it’s set to “Use Scene Environment”
-Roughly model floors and required walls, then apply the appropriate Matte/Shadow/Reflection (Floor or Walls) material to each
Create a very large cube that encompasses the entire scene. Convert to poly, delete the top face, transpose it down a little in the Z direction (so it doesn’t intersect with the floor), and apply the Walls material to it. This is to catch reflections, rather than having ugly white reflections. I don’t know why it works, but it just does for me.
That’s about it. From there, I simply import or create my models, texture, and render. Then I go back and adjust the reflection of the floor as necessary.

Now, I just need a similar process for VRay. I've been experimenting with settings and scouring the web for solutions for weeks, and just cannot find anything that does the trick

Really hoping I can get a little help, or even a shove in the right direction, it would be massively appreciated.


Thanks all

[mcnamex]

nice sets of images

[Jorq1H]

Hi danimation3d!

This is something I'm doing a lot of myself, and as yourself, also coming from an MR-workflow.
Now, the materials setups your describing above should be pretty straight forward in Vray as well.
Unfortunately, Vray doesn't have a environment/background-switcher (to my knowledge) as MR does. But this is easily fixable. Simply add your background in the environment slot, and in the render settings, activate illumination override (under environment) and set it to pitch black. Now you'll avoid having the background image/video also act as environment light.

To get reflections, simply activate the refl/refr in VrayMtlWrapper settings (for the reflections material) and make the base material reflective as needed.
Beware, that if you're using an environment light like the VrayPhysicalSky or an HDRi, this will be visible in your matte reflections. Simply do the same as with the environment light above (override, completely black), and add the environment to the environment slot of whatever reflective object you decide to put in your scene.

You mention creating a large cube to avoid ugly white reflections. I'm not quite sure why this is needed. Perhaps it is related to the global reflections I mentioned above?

For lights, I would suggest using either VrayLights (rectangular) placed at each window or just one VrayDomeLight (turn off specular/reflections/visible). This will create the soft shadows you need, but also, being direct light(s), you'll get full control over visibility and shadows. This, of course, is a matter of personal taste and decision. I'm just throwing it out here.