"Alpha Over" Equivalent in Hitfilm
Hello, I hoping this is newbie problem, and that I am misunderstanding something fundamental with Hitfilm.
I have a problem with some composite shots not combining with the alpha channel properly. Here is picture which points out what the problem is. On the left is my composite from blender which I will post below. For context:
- I am using a technique to reduce render times for volumetrics by combining 2 separate renders of the volmx one done in Eevee and the other in Cycles with de-noising. Also the cycles render settings are specific to the scenes, volmx and background, and therefore render much faster. Altogether there are 3 layers in this composite.
- The main scene has everything but the volume, and the volume layers has everything except the volume held out - as an alpha channel.
- Blender has the "Alpha-Over" node, which I think is the reason why it is composting "correctly" (ie the way I intend) and I can't work out why I can't find an equivalent in HF.
- Although I should in theory make composite shot first to mix the volume, I should still have alpha channels allow through the background, or block the background depending on the texture.
Note the bubbles which are not allowing through the background, and the fish which should be blocking the light. I double checked the EXR files and re-composited in blender - ie reconstructed my composite from my render file with the exr files incase something funky happened. But there isn't they composite as I expect.
I can't help the feeling I have missed something really obvious. I have reconstructed the composite as closely as possible in HF using the same blend modes and colour adjustments, but what I should see simply by putting just one volume layer on top of the main scene without any corrections (using "normal" blend mode), is the colour of the background coming through the bubbles, and the fish blocking the light.
I could post single frames of the composite, 1 from each layer if it would help. But hopefully (certainly) it is something I have not understood.