Add mask to scaled down image in DaVinci Resolve Fusion

[Nicolas Hanson]

I want to scale down the image and draw the shape on top of the scaled down image, sounds quite simple but I can't wrap my head around how this is processed.

I  scaled down the image with a transform node , and now I want to use a b-spline to create a mask. When I draw the shape and connect the b-spline to the media input it automatically scales down the shape. It's like it's applying the scale data from the second node (transform node). Why is this happening and how can I avoid this? I know I can add the spline after the transform (on the merge node) but that doesn't allow me to go back and change the position of the shape and the image simultaneously later on if I want that.

Edited May 12, 2020 by Nicolas Hanson

[Nicolas Hanson]

It looks like this is just an issue with the b-spline. When I add one of the other masks to the alpha input of the input node it doesn't change the scale. Is this a known bug? Workaround?

[Lee Lanier]

Connecting the mask to the Effect Mask input of the MediaIn node gives me the behavior I would expect: both the mask and the footage are scaled down by the Transform node. However, there is some weirdness connecting a mask to the Effect Mask input of Transform node - the mask seems to use the un-transformed version and you get a weird amalgam output.

A workaround would be to leave the mask connected to MediaIn or to use it further downstream. For example, add a Merge. Connect the Transform to the Merge FG input, the mask to the Merge Effect Mask input, and a Background solid color (with Alpha set to 0) to the Merge BG input.

Edited May 12, 2020 by Lee Lanier