Cineversity

Hello
I’m trying an effect where I’m using a fake video projector to project on an object in C4d.  So I’m using camera mapping as a texture projection method.  Now what I’m trying to do is for the texture to essentially be “black” or not affect the areas that are occluded from the camera frustrum (which would be the rays coming from the projector).  Seems like a very simple task and I’m probably missing something obvious, but can’t seem to get that kind of occlusion…

Thanks!

Hi Alex,

The Camera Projection has no shadow option. To get this done, a light source must be employed.

This is a little bit more tricky than the camera mapping, but having a camera mapping set up is certainly a needed guide.

I have set up two scenes, “…_01.c4d” and “…_11.c4d”:
https://www.amazon.com/clouddrive/share/5r4KWdst32UkUR4oEj2l45UIetuOJlc8NvQCxOwsodW
Have as well a look at the screen-shot.

Please start with the …_01.c4d file to get an idea about the set up. Since the flat projection will not come anywhere close to camera projection, file …_11.c4d is set up with a Spherical Projection.
Please note the set up of the shadow and the Light> Details to get an evenly lit projection.

Additionally, one can rebuild just a projector:
Scene file “…_21.c4d”
https://www.amazon.com/clouddrive/share/KoEcpOhVArBatqhPYCxKlH1bDqckn8xnaivAH4k8Njv

Brainstorming: An Alternative would be to use the camera mapping, but have a light source first recreate the Frustum of the camera, and cast so the shadow, this needs to be backed on the object. The additional information of the camera projection should result then in the wanted appearance.

I have done this for a music video, kind of, to introduce the shadows of a billboard on the walls.
https://www.youtube.com/watch?v=fYNJd9QGHGo
You will find on my YouTube channel as well a little making of, for this clip.
https://www.youtube.com/watch?v=mSWrLLlGyJo&list=PLOLI4wu7NPsijH80qg6XvNZdUhlf2Ic5d
A screen-shot of the camera mapping with the “painted” shadow from the billboard is here:
https://www.amazon.com/clouddrive/share/GUXZgpg1V1dKRthgT0hqYNx7jlI5BrOb16LdvwVyVqr

All the best

Wow, great trick!  Thanks for sharing!  The projector trick is really super useful, I can definitely use that on a lot of things…

Thanks again Sassi, and thanks for sharing the making of the video!  Great to see your process.

You’re very welcome, Alex. Thanks for the feedback.

I like to share and certainly try to share different ways, so one can chose or mix. I certainly believe there is always an advantage to have not just one way to rely on.
This music video was one of several projects for me to explore 4K workflows between Cinema 4D and my RED footage. Lately I looked as well into Canon log and how that would match with C4D. There is always something new to explore and to learn.

If your project needs anything different, please let me know, I’m happy to look into it.

My best wishes

P.S.: I mentioned above the baking option.

Please check the scene file and the one minute clip:
https://www.amazon.com/clouddrive/share/CsIlJJgiS6ZA3klB7263EnMOXjBMkTl8vPffJffaih2

There are a few steps to do, and I placed the main steps into the Take System. This is documented in the one minute clip, including the final material set up.

Please note that adjustments in the Diffuse Channel [Mix Strength] will change the shadow strength.

If the Camera Projection/Mapping is based on a video file, then backing this source would be not advised. I would suggest in that case more the following set up, which is all based on the Texture Tag set-up. Most right sided tag is set to Attribute Manager> Tag> Mix Textures. The next Tag holds only an Alpha based material, which shows the Projection [mix] only on its own visible parts. The left sided Tag is then a material to represent the shadow, but can also provide other options, e.g., reflections.

Scene file
https://www.amazon.com/clouddrive/share/0nJooYESRJy9jPbUmHexPgnawgSrd5ZxkgZgQjpE7FX

ENJOY.