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Sorry I'm new, i can't find a tutorial to do this: i have a normal video and another one that i would like to use as an alpha mask to 'smooth borders' in davinci resolve, here is an example of my mask

enter image description here

Can i do it on DaVinci Resolve? I suppose i should do it in Fusion, but can't figure out how.

Thanks

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You can simply add it to Fusion, and then pipe the alpha video into a MatteControl node. Alternatively, if your image does not have an alpha, but is just black to white gradients, you have to first go into a bitmap node like this:

Mask image piped into bitmap node

Now configure the bitmap node to use Luminance instead of Alpha as the channel:

Setting channel to luminance for bitmap

Now you can use the output of that bitmap as a mask in the blue inputs of nodes, or as mentioned in the MatteControl.

Or if you're using a Merge, you could also pipe it into the mask input of the merge node.

You could in theory also pipe it into the blue mask input of the source footage, but that makes it so every instance of that footage will have the mask applied, so it's not reusable, which we generally try to avoid.

So you can see the full setup here: (Note that Garbage mask of the MatteControl has to be set to invert) Full node setup

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  • Both MatteControl and Merge have multiple inputs and a ton of settings. I have tried both and couldn't get them to do this dead simple masking. Davinci nodes are quite frustrating :(
    – mik01aj
    Commented Feb 21, 2023 at 19:44
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    Hi @mik01aj I added an explanation that shows how to do it with an image that doesn't have an alpha channel (Which I assume is your issue). Nodes can be a bit difficult to learn at first, but make things much easier once you understood them :) Don't get discouraged! If you're still confused, you could join the Blackmagic Discord: discord.gg/blackmagic-design-community-479297254528647188 where people are happy to help and it's easier than on Stack Overflow :)
    – Timothy Lukas H.
    Commented Feb 22, 2023 at 20:18
  • Thanks for the details! The thing that confused me is that I need a bitmap node to convert an image to a mask (I'm guessing this is what it does). I'm coming from Blender where nodes are generally much simpler and they convert the datatypes automatically.
    – mik01aj
    Commented Feb 22, 2023 at 23:17
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    The issue is that Fusion wouldn't know what your mask should be. Every image node has basically 4 channels: Red, Green, Blue and Alpha. You can use the image as a mask input, but then always the Alpha is used as such. So now to tell the program, that you want to use the RGB channels as mask, you put them through the bitmap which selects which channel (In this case luminance - the mix of RGB) should be used as a mask.
    – Timothy Lukas H.
    Commented Feb 24, 2023 at 7:50
  • Had a similar need and didn't find a ready answer. Also very new using fusion. I ended up doing most of what @TimothyLukasH. described except I piped the bitmap straight into the clip that needed to be masked. Worked perfectly
    – MichaelH
    Commented Dec 11, 2023 at 16:54

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