Shadow Catcher: Is backplate geometry projection possible?

[Karol Nord]

Hey everyone,

I am wondering if it is possible to project the backplate of a shadow catcher material onto geometry through a main camera, while using a different camera to move through the scene, creating a parallax effect. I tried setting it up in the latest Corona for C4D beta but the backplate always seems to be projected through the active camera.

On this image you can see a backplate correctly projected onto geometry, with the respective corona rendering result. The backplate seems to be accurately projected onto the surrounding geometry since it is showing up correctly on the reflecting sphere.


Here you can see a separate camera being offset to create a parralax view


As you can see, it doesn't output the result i was hoping for. The Shadow catcher material in C4D only offers frontal, spherical and cubic projections, not a camera based projection, which is likely the the issue.

On the look out for alternatives, i tried inserting the shadow catcher material into RaySwitcher material with a camera based projection, but that doesn't seem to work.
Using an unlit (illumination only) material projected onto the geometry works nicely for the parralax, but obviously isn't able to recieve any shadow information.

Can anyone offer a solution or workaround to my issue?

If this isn't possible right now, i'd love to see this feature in upcoming versions!

[Karol Nord]

No one with any insight on this? Or is my description not clear enough?

[sprayer]

Yes this is not very clear, also it's 3ds max section, many users here don't know that software. Don't know why moderators do not move this topic

[Karol Nord]

Okay. My question isn't specifically related to the c4d version. If it works in 3dsmax then there would be good hope that it either already works in corona for c4d or that it will be implemented along the way.

if you have a look at the wrong.gif attachment you can see what happens when you put the shadow catcher material on the geometry reconstructed from the photo. When moving the camera around, the backplate is always a frontal projection into the scene, and the sphere, which initially sits on the floor and next to a wall just drifts away. No parallax is visible.

On correct.gif you can see what happens when i use a standard diffuse material camera mapped onto the reconstructed geometry. When moving the camera around, you see the depth parallax. This is almost the result that i am looking for!

The problem with this solution is, that the reconstructed scene geometry is being globally lit and shaded which is not what you want when you are working with backplates.

i hope this is a bit easier to understand?

[romullus]

Your "wrong" gif isn't working, but i think i know what you mean. Shadowcatcher has only screen and spherical projections, it can't do camera map projection, like ordinary bitmap node can. I think it's the same in 3ds max too.

[Karol Nord]

Okay i see. Thank you for shedding some light onto this. I already noticed that the shadow catcher only provides frontal, cubic and spherical projections but i hoped there might be a different way to get this to work.  I guess i can propose this in the featue request section.

I suppose there is no other kind of workaround available? Something involving the rayswitcher and/or compositing tags? I haven't been able to find one myself yet.