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How do I make an object invisible that can block light?
Hi all,
I’m working with a Cinema 4D Lite project in After Effects. I’d like to make an object that won’t be seen by the camera, but will block light behind it (specifically, parallel spot lights).
So far I’ve tried to disable “seen by camera” in the Compositing Tag, but then the light behind the object is visible.
I’ve also tried using the Object Buffer to create an alpha channel. This works when the light is behind the object, but later in the shot the light moves in front of the object and then the light is obscured by the alpha channel.
I am new to Cinema 4D, so perhaps I am missing something obvious? And apologies if this is answered elsewhere—I’ve spent hours searching for an answer, but have not been able to find one.
Thanks in advance for your help!
Ben -
4 Replies
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Have you set your light to cast shadows?
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Hi Adam,
Thanks for your suggestion. The lights were not set to cast shadows, but unfortunately enabling shadows doesn’t resolve the issue. However, I did a little experiment and created a spotlight to see if the light from it would be blocked by one of these objects, and sure enough that worked. But then I made the spotlight visible to see if the object would be able to block that light and it did not.
That’s an important bit of info I didn’t really specify in the original post—the lights are all parallel spots with Visible Light set to Visible, so the lights I’m trying to block are the parallel spots themselves. I’ve attached a screenshot of the viewport to give you a better idea of what I’m trying to do. I want those tubes to be invisible in the final render, but to block the light from the parallel spots running through them.
thanks!
Ben
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A friend of mine suggested a workflow that fortunately addresses the issue that I was having.
He suggested creating an alpha channel based on the laser beams. I wasn’t able to create an alpha channel from the parallel spots that make up the laser beams, so I just created some simple cylinders along the beam paths and added them to the object buffer. Fortunately, this works! Before, I was using the objects that the beams pass through for the alpha channel, but that didn’t work because the beam would be blocked even if the beam was in front of the object.
Thanks again for chiming in, Adam.
cheers,
Ben -
Here’s what the alpha channel ended up looking like.
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