As the title says. I’m kinda familiar with the node editor, but rewiring it to output my 3d element with alpha, from a matchmoved/camera solved scene, is proving too much for me, I keep getting my elements with a white background when I try to render. I can see that my 3d is being combined with something (even after I unplug my movie clip node). My node tree is that create by the camera solver when you create a scene with it.
KINDA SOLVED UPDATE: As Set up tracking scene creates 2 layers automatically ; Background and Foreground, plus a node tree. I decided to start from scratch. Created a new layer, then deleted both Background and Foreground layers. Now, when I hook up my Render layer to the Viewer/Composite output I get exactly what I want. I’ll mark this as solved, but if anyone can explain this behaviour I would be much obliged.
The node tree was automatically created. I just disconnected my background movie. So I really don’t know why. I guess that if I remove that final add node? I presumed it was something to do with alpha manipulation. I come from a layer based compositor so am still getting to grips with the blender compositor. Thanks for your help!
Ok, I tried deleting that node. Still I get my render on a white background. In my renderer I have foreground, background and composite layers. I can select my foreground and get my render with alpha. But, I can’t seem to access this from my RGBA png export. I had hoped deleting the add white node would solve this, but it hasn’t. What am I doing wrong/missing?
UPDATE: As Set up tracking scene creates 2 layers automatically ; Background and Foreground, plus a node tree. I decided to start from scratch. Created a new layer, then deleted both Background and Foreground layers. Now, when I hook up my Render layer to the Viewer/Composite output I get exactly what I want. I’ll mark this as solved, but if anyone can explain this behaviour I would be much obliged.
Shadow and AO passes do not have alpha. When you AlphaOver the Fg over BG there is no transparency left. You must add alpha explicitly to the result you create from AO and Shadow passes by Set Alpha node. And to get alpha in the first place, you must render some pass that has alpha channel enabled (Combined is the only option actually).
When you trace the image with eyedropper tool you can sample the pixels and see what RGBA channels actually contain. If something is wrong it is a good place to start exploring. When alpha is 1.0 everywhere it tells you that either there is no alpha enabled in that pass/element/render or something filled the alpha in current or some previous node.
Looks to me that the invert node near the top left is to blame - not quite sure what you are using it for - trying to make the contents of the image white only?
Thanks for this, I come from After Effects, so I know how to troubleshoot practically anything in that, so coming to new software and not know basic troubleshooting techniques causes so much frustration!
