[Wynott]

I'm trying to get a look where there is basically a solid colour background, but with an invisible groundplane to cast shadows on.

Any bright ideas on how I could achieve that?

Jeremy suggested:

I think that what you want to do is to create your plane, apply a material which has both Shadow & Matte enabled (in the top-level material properties), and then make sure to enable Output > Channels > Shadow. Otherwise, please ask the question out in the main forum, since I'm far from being an authority on how the compositing features are generally used.

But I didn't get the shadows. Not sure what I'm doing wrong.

Rhino v5

[seghier]

you can do that with composition ; maxwell render don't have this option
you find more informations in online documentation

[Mihai]

This is the page in the docs that talks about the shadow channel:

http://support.nextlimit.com/display/mx ... ow+channel

To summarize you need to do 3 things:

1. Check the 'shadow' option in the material applied to the ground plane so it will act as a shadow catcher.
2. For the object that sits on the plane and will cast the shadow, in the Maxwell properties of it, check "Hidden from camera in shadow channel"
3. In output options, channel section, make sure the shadow channel is checked.

Then you can composite the two in an image editor, you just put the shadow channel render on top of your main render and set its blending mode to Multiply. Your file will have three layers: bottom one is your solid color, middle one is your object cut out using an alpha channel (http://support.nextlimit.com/display/mx ... ha+channel), top one your shadow channel render set to multiply blending mode.

[Wynott]

That worked perfectly. Thanks Mihai...

Should it be possible to isolate an object on it's own channel?

I'm wondering if I can render a boat with the sea separate? So the base image is the hull including the underwater parts, then with the sea on another channel... So I can get two versions of the image from a single render?

[Mihai]

You will not be able to get two "beauty" renders from the same render, but you can use custom alpha channels to specify which objects will belong to that extra alpha channel and use that to easily select parts of your main render in your image editor. Custom alpha channels also work per material.

http://support.nextlimit.com/display/mx ... ha+channel

In the Rhino plugin you would first create these extra channels in the Output options, in the Scene Manager panel, then depending on if you want object custom alpha channels or material ones, you would add that same name either in the Maxwell material properties or the Maxwell specific object properties.