matte/shadow/shadowcatcher confusion

[AndyQ]

I'm a bit confused about how the shadowCatcher material is supposed to work or even if it is intended to perform the task I have in mind. In MentalRay I use the Matte/Shadow material to catch shadows from objects sitting on a floor so I have a render of the objects with their shadows and the rest of the floor is transparent in the alpha (completely transparent). Underneath the "matte" floor I've got a different, textured floor which interacts with the lighting of the scene, but the matte object doesn't. I guess my question is this - can I use the shadow catcher in some way in which it doesn't influence the lighting of the scene at all - in my tests thus far it always seems to have some contribution. It also seems never to get completely transparent. I'm not sure I'm explaining this well, but basically I just want to get the shadows on a floor sent off to a separate render for compositing. Ideally I'd like reflections too for some other tasks. Am I going about this completely the wrong way? I'm fairly ignorant about this kind of stuff...

[maru]

Hi, have you seen this guide+video?
https://coronarenderer.freshdesk.com/support/solutions/articles/5000554427

It looks like you will need to set the shadowcatcher alpha mode to "for compositing" and change your direct visibility override to pure black.

If you wish to exclude the shadowcatcher from GI for some reason (you mentioned you do not want it to affect other objects) - you can nest it inside a CoronaRaySwitch material and plug it into all of the slots except for "Global Illumination" (this slot should be cleared). You can do the same for reflections and refractions.

Please let me know if that's what you needed. If not, it would be great if you could provide us with examples of what you would like to achieve.

[AndyQ]

I'm using Corona 1.3 for MAX, commercial version. I'm basically after a material that works the same as the Mentalray Matte/Shadow/Reflection material. I'll try playing with the Rayswitcher/ShadowCatcher combo although I 'm not sure I can fathom what it's all meant to do...

[AndyQ]

Let's put it this way: Say I have an object that is the floor in my scene, this has a material with a colour, shininess etc. There are objects on this floor casting shadows on to it. What I'm after is some way to get a channel to mask out the floor except for the areas that have shadows and reflections - i.e. I'm after some transparent shadows. This is for use in making transparent PNG's for a website - I want the floor to affect the scene lighting but then remove it entirely and just keep the shadows (without the scene illumination changing). Hard to explain!

[AndyQ]

......and change your direct visibility override to pure black.

Hi - Where do I find this "Direct Visibility Override"? could it be called something else?  - cheers, AQ

[maru]

The override is in render setup > scene > scene environment > environment overrides - the one which you need to set to black (if you are using some kind of background in your scene) is "direct visibility override"

So basically you want to extract the object which is on the floor + its shadow on the floor + its reflection in the floor?

[James Vella]

Hi,

Im using Corona 1.3 and having some difficulty with the shadow catcher. I want to do basically a 'render selected' as you would do in vray but im getting some odd results in the alpha.



This is how it looks combined. However I want to separate the people and keep the shadow/reflection as it appears here.

When I render the background it looks fine. I then select the Render Dialogue > Scene > Render Override and render the people with the "Corona Shadow Catcher Material' in the Mtl override: section and the people excluded I get strange shadows on the ceiling (no lights are pointing up) and its very noisey.

Scene


Override Settings


People + Scene


People Alpha


I also tried enabling reflections after this to see if that would help, but it almost seems like a total override - disregarding carpets and other gloss materials with its own. I tried both 'use matte projection mode' and not, still the same result

With Reflections



Anyone come up with a solution for this?

[James Vella]

bump o.O

[3di]

Just apply a shadowcatcher material to your floor and set the direct visibility override to black in the render settings-scene-scene environment-environment overrides.  If your using render selected, and only want the people and their shadows, you'll need to select the floor as well as the people.

[James Vella]

Thanks. That's a good workaround for now.

I do so want all the minor and major reflections in the glass cabinet, floor, windows as well... am i asking too much  i wonder? Lol

[3di]

No, should be pretty straightforward, just render the full scene with the people hidden and the textured material re-applied to the floor.  Then superimpose the people and their shadows back in an image editing software.  If you need the reflections of the people in the windows etc, just select those objects too when you render out the people and the version of the floor which has the shadow catcher applied.

Personally i''d just render it all in one pass with the people visible and the textured floor material, unless you need to supply two images, one with the people and one without.

[James Vella]

The people will be animated (definitely want them separate), so I need different reflections for the floor, windows, ceiling, some panels, each have different gloss etc. Im going to assume there is no correct matte pass available yet for Corona. Also, applying black to everything will not give a -1 Alpha, this is also an issue.

[Eder_Xavier]

Hi
Have you found any practical solution?
I´m having the same problem on my animation........... :(

[vl_dm]

Hi Andy,

I have the same struggle here, have you come to any decent solution?