How to use roto shape to change transparency?

Greetings I have a few shapes on a roto node, and would like to use these shape to cut holes into an image, but I would like to control the transparency strength all at the same time and not go shape by shape on the roto node.

Is there a way to tie in the roto shapes into a blending node that will go from background fully opaque to fully transparent, but only within the roto shapes? Thanks!!!

If you select multiple roto shape, changing the Opacity is adjusted for all shapes simultaneously.

You can also adjust the Amount slider in a Composite node.

Hi Marco, I’m familiar with selecting multiple shapes within the roto node, but I was hoping there’d be a quicker way to just use another node to control my opacity for the roto cut outs rather than having to pick the node, shift select all the shapes, then change the value. Any way to do this? Thanks!!

I previously mentioned that you can use a Composite node and and adjust the Amount slider. This will control the opacity of the foreground.

You can also use a Matte Repair node after the Roto node and adjust the Opacity.

Ah ok, so from testing it out, it looks like hooking in any source to ‘Matter Repair’ and changing the opacity on ‘Matte Repair’, is what I’m really looking for in Silhouette, where it “seems” to work exactly like adjusting the opacity slider of a single layer in After Effects from 100% (Fully opaque) to 0 (fully transparent showing the alpha background only). Would you agree?

Using a composite node for adjusting opacity on the foreground only seems to work when you have something hooked into the background, do I understand this correctly?

With regards to importing a something like solid red circle that shows a checkerboard/transparency in photoshop and I export it as either a PNG or TIFF with transparency, would I “always” keep either source set to Type: Straight - Unmatted? If not, when generally might I use Type: Premultiplied for my source?

Thanks again!


That’s correct.

Silhouette is a straight, unmatted compositor and its composite nodes expect unpremultiplied images. In addition, it is best practice to unpremultiply before color correcting premultiplied images so as to avoid unexpected results. If you are working with premultiplied images, you have the following options:
• In the Source parameters, identify the alpha as Premultiplied. This will unpremultiply it.
• Unpremultiply the image within the Composite node.
• Use a Composite > Unpremultiply node before the premultiplied image hits the Composite node.