-
100% Transparent Object still creates an Alpha
I have a polygon-heavy model translated from a CAD file, and I’m trying to fade out the shell to show an interior element, but when I try to fade out the outer shell objects they disappear in the RGB channels but still produce an alpha in areas with high polygon densities.
Making the material 100% transparent or 0,0,0 alpha still leaves an alpha in some portions of the render. If I add a Display Tag and take the visibility down to zero the alpha will go away, but if I have it at 1% or higher I get 100% alpha in those problem areas.
After some tests it appears that the polygons’ orientation to the camera affects which areas show up in the alpha channel.
I’ve posted a 700 KB project file that distills down the issue. It includes a section of the model I’m using with one material with just Color and Alpha enabled. Alpha is set to Soft, Color: 0,0,0. The camera pivots around the model from frames 0-10. Render frame 0 and look at the alpha channel. I’m getting 100% alpha over part of the model.
Render frame 10 and the alpha is totally clear (no white visible in the alpha channel.)
Is this a bug? Some switch I’m missing?
I was hoping I could do this in one pass, but I’m thinking I might have to render the beginning and the end with an overlap and do the dissolve in After Effects, but that seems more complicated than it should be. I have the feeling I’m missing a checkbox somewhere.
I’m using R.11 on an Intel Mac Pro.
Thanks.
Shawn Marshall
Marshall Arts Motion Graphics -
5 Replies
-
try animating the color in the alpha channel instead (or at the same time depending on what you need)
-
Hi:
Thanks for the reply. As I mentioned several times in my post I have tried animating the color in the alpha channel. An alpha with the value of 255,255,255 (white) creates a pure white, 100% alpha. An alpha with the value of 0,0,0 (black) makes most of the alpha zero, but some parts remain with 100% alpha, depending on the orientation to the camera.
Could you download the C4D file I posted and confirm what I’m getting, which is partial alpha on frame 0 and no alpha on frame 10, even though the alpha is set to 0,0,0 throughout?
Shawn Marshall
Marshall Arts Motion Graphics -
I did dl your scene but was expecting a Display tag and that distracted me I guess… I think I understand now, increase Ray Depth in your Render Settings, it’s not high enough and you have too many layers to go through for the alpha to be complete (dependant on camera angle to the object)
-
Ding Ding Ding Ding!
We have a winner! Upping the Ray Depth to 50 made the alpha render properly at zero.
…except when used in conjunction with an Environment Object with the PyroCluster VolumeTracer tag. Even when I crank the Ray Depth to 500 I still get some objects with 100% alpha where there should be zero. I’m using PyroCluster to render the dirt particles I’m generating in this scene.
Any guess how to get around that, besides rendering the particles by themselves and compositing them in AE?
Thanks again for taking the time to look into this. I really appreciate it.
Shawn Marshall
Marshall Arts Motion Graphics -
Well, still learning here. I thought the Environment object with the Pyrocluster VolumeCluster had to be visible to the renderer for the dirt particles to be visible, but apparently it doesn’t. So things seem good now.
Thanks.
Shawn
Reply to this Discussion! Login or Sign Up