Colorize hidden parts from camera projection I am doing a camera projection (from a picture onto a 3D object). In the picture I am projecting from, there are some hidden parts of the object due to the geometry of the object itself, and I would like to avoid Blender to &quot;invent&quot; those hidden parts of the texture by repeating other visible parts so I can know accurately and quickly which parts are still needed to be photographed in order to complete the full texture of the object.
My idea is to bake the projection over a green chroma texture but I do not want the UV project modifier to complete the texture regarding those hidden sections of the 3D piece (which is currently doing).
Does anybody know how to avoid that?
EDIT:
Just discovered the image is being projected onto every voxel colliding with each ray from the camera, which means it is being projected onto backfaces where (in my opinion) it should not. Researching deeper in this, I just found a topic which describes my problem and potential solution:
Cycles, UV Project Camera Modifier projects forwards and backwards
It suggests to use object's negative Z coordinates to &quot;blank&quot; those parts of the texture and therefore avoid printing backfaces. Is there any other solution?
Tell me if you consider to remove or to solve this thread or mark it as duplicated in case there is no other possible solution.
Thank you again for your feedback.
Best regards,
maije
You've indicated a few details in your comments: you're using the perspective of the camera for your UV projector; you want to do this using only scriptable tools (no mouse strokes).  For that, the linked answer you gave won't help you.
You need to make a mask for your projected image.  As I indicated in comments, the easiest way to make this mask is just by hand, with texture painting.  But it's not impossible to do it another way:

Make your object flat shaded.  Give it a diffuse material.  If it's not UV mapped, give it a non-overlapping UV map (a smart project or lightmap project would be fine.)

Place a point light at the location of your UV projector camera.  Set the radius to 0 and the light to something really high (like 100,000).

If necessary, remove everything but the object and point light from renders.  Set bounces to 0.

Create an image texture node in your material and bake combined to a new image.  Save your image.

Create compositing nodes using your baked image (not a render).  For each pixel of your image, check to see if the brightness is greater than 0.  Make your output 1 if it is, 0 if it isn't.  Set your color management display device to None.  Set your rendering resolution to the same resolution as your baked image.  Render.  Save the render.  As necessary, revert to settings used at the start of the process.


You now have a mask created using only scriptable operations that represents the occlusion (only) from your UV projector.

Let me know if that image is bugging out for you-- Imgur looks like it's freaking out or something.  Check comments for a different image host.