Operating system: Arch Linux
Graphics card: GTX 1060
Short description of error
If I import a scene with a transparent background into the VSE as a scene strip and set the blend type to "Alpha Over," any curve modifier will affect the alpha-ed area too, flooding the area the strip covers with the adjusted color. It appears this only occurs with scene strips. Image and video strips with an alpha background appear to behave as expected.
Exact steps for others to reproduce the error
- Create a new scene with an alpha background.
- Add some meshes, lighting, etc to that scene
- Add a camera to that scene pointed at the stuff you added
- Set the scene's shading to transparent
- Add the scene from step 1 to the VSE
- Switch to video editing mode
- Change the scene back to the original Scene instead of the one created in step 1
- Add the scene from step 1 into the sequencer
- Change the scene strip's "Blend Type" to "Alpha Over"
- In a channel below, add an image strip or a movie, or even another scene strip
- Adjust the color of the scene strip using a curve modifier
- Render out the image and notice that the curve modifier is affecting the area that should be alpha.