Gaining Up Plate Produces Different Results Compared to Nuke


Something I’ve been noticing recently when doing roto on very dark plates you often need to gain up the viewer a lot to see edges clearly in Silhouette. However the colour overlay stays the same luminance whereas in Nuke, when doing the same thing this actually changes the colour overlay and the alpha becomes more/less crunchy.

Just wanted to find out really if there is a way for the gain behavior to match at all and why there is a difference between Nuke & Silhouette? It’s never been a huge issue but on this current project its very easy to see motion blurred edges in Nuke that are too far out/in whereas in Silhouette its not as obvious at all.

Sorry I can’t post images.

Does this help at all?

Unfortunately not Marco. Basically when viewing rendered roto from Silhouette in Nuke or in RV if you gain up or down, the colour overlay also gains up & down which means semi transparent motion blurred edges become crunchier and its really easy to see where the last pixel of your motion blur actually ends compared to the plate. Whereas when working in Silhouette, when you gain up or down the alpha & colour overlay stays exactly the same and it actually more difficult to see how far exactly motion blurred edges extend to. I tried playing around with the colour overlay opacity and
I’m not sure if it’s potentially these dark sourceplates specifically or not as I’ve never noticed this being a big issue in the past.

Just wondering is there a way we can replicate in Silhouette exactly what I see in Nuke or RV if I gain up by the exact amount with the same LUTs etc?

I think I see what you are saying. Silhouette’s Gain and Gamma viewer controls don’t affect the alpha. It has always been this way. You can use a Swap Channel node after the Roto node and set the RGB channels to Alpha. This way you use the Viewer > Gain and Gamma controls.

Thanks Marco, that helped. I did actually just end up using a colour correct with the roto as a mask to create a manual colour overlay which then responded to the gain/gamma viewer controls. Never been an issue before but thought I’d just ask around as it was causing some small issues. Cheers!

We’ll see if we can have the Gain and Gamma also affect the alpha channel.


Just coming back to this post because this difference in the colour overlay visualization between Silhouette & Nuke/RV is a real issue on my current project.

I am now using a Swap Channels node plugged into the roto node with the Red set to Alpha. When on a viewer gain of 3 it is immediately obvious with this where motion blurred edges are not matching exactly, compared to the standard alpha overlay view on the roto node. Sorry for lack of images, you might be able to recreate a similar scenario with some dark stock footage of a close up turning face perhaps?

Anyway my question is, is there a way, perhaps through the script editor, to have the Swap Channels output accessible with a keybind shortcut when using the roto node? I’d love to be able to press Shift A and this is my custom colour overlay rather than the default Silhouette one? Currently I have to keep switching between the nodes manually. Sorry bit of a bespoke request I know but it would be really useful.

Let me know what you think. Cheers

1 Like

That’s so useful if we can assign a keyboard shortcut for the above situation. I always dream about an update in silhouette, with the same nuke viewer properties!

The view shader (resources/shaders/viewer.glsl) bypasses OCIO entirely when viewing the alpha channel. Is there a different color transform you think it should have?

Hi Paul, not an expert in this area by any means. All I know is the discrepancy between Silhouette & Nuke/RV is quite significant when matching motion blur on dark plates and is causing issues in roto QCs currently.
I’m not sure exactly what I want in technical terms but would having a preference option not to bypass OCIO make alpha’s be affected by viewer controls? Any short term solutions other than what I’ve already set up with the Swap Channels node to override the default alpha overlay view most welcome though.

For the next Silhouette release, we plan on allowing the viewer controls to also affect alpha.