Premultiply

[majush]

Suddenly I feel all clueless. Any help is appreciated.

Olden days there was a curve inside the old keyer which removed the black edges from cg. Then 2013, punchback blend mode workd. 2014, I cant seem to find any ways. Where should I look for removing the black edge from cg renders?

thanks

majush

[ManChicken]

If you are in Batch land and combining with the Comp node, there's a Premultiplied/Unpremultipled toggle for both the Input and Output.  If it's a Matte container out on the timeline, the Comp effect there has the same toggle to say what the source is.

[majush]

thanks a lot. But am afraid it doesnt seem to be of working as expected. the black edge somehow remains till i use shrink.

[ManChicken]

Hmm. Are there any other effects involved, or is it just plain, composited over a background?  Is the source an image sequence such that you could upload a frame of the original fill & alpha to take a look at?

[A_Over_B]

When nothing else works use pixel spread:

Divide the fg by the alpha.

Pixel spread expand the divided fg by the alpha.

Comp the pixel spreaded fg over a bg with the alpha.

[ollieslats]

Have you tried Analyze / Z-Sort . when I've had the same issue that has fixed it for me.

[majush]

just simple front and matte over a lighter bg. so far only pixel spread helps. divide works on some halos. I really wonder why the old school stuff got taken down. I heard somewhere that punchbak transparency is meant to do that same job and in 2013 i remember it worked. now in 2014, all hope is lost and cuddling pixelspread on a regular basis.

[lcrs]

The same curves that used to be in the old Keyer are still on every Action surface in the Blending controls.  And I think there's still a Matte Curves node in Batch which does the same thing if you use it to do the comp 🙂

[erikliles]

Use a LogicOp Divide ( Front: RGB, Back: Matte ) as the first process. Then any CC you do will not add any more dark edges. But if you want to blur the element you will need to Multiply it by the matte, Blur it, and then Divide it again before using a Blend in Action or a LogicOp.

You can Also use QuickComp in Additive mode to achieve the same result as Punch back in Action.

[Grant.Kay]

Hi,

Technically, using the blend curves was never the most ideal way of dealing with edges but it did perform an additive key.

However, if you do want to use them in Action, the blending curves still exist.

They should be located in the surface menus when you select the image in action.

By default it is set the to keyer curves. But you should be able to alter this and set the curves to behave the way they did in the past.

Hope this helps.

Regards
Grant

[majush]

I have checked that curve but it do not behave the same way it used to be.

[Grant.Kay]

Interesting.

Just a thought, the reason why we used those curves was because we never really has the numerous blending modes in Action all those versions ago.

This is not the case now. Reset the blending curves back to the way they were. In the surface menu, change the blending modes to add or what ever works.

If not you could also try this.

You could try going into the modular keyer and selecting the result node.

There is a set of blending curves you could try there as well.

But like I said, if you are attempting to correctly sort out a premultiplication issue than you need to look through the Blend and Comp node. (and the new Comp node in Smoke 2015)

These tools correctly handle these issues with premultiplication.

[majush]

Thanks Grant. Will check them out as soon as I can.

[andy__dill]

If your CG doesn't comp correctly when you divide the front and matte (or with the new comp node set the input setting to Premult) then the issue is with the CG, not with flame.

You shouldn't be using the curves to comp CG these days anyway.  That was a seriously old workflow from the days (pre flame 😎 when dividing wasn't avaialble, and even less necessary with the new comp node.

Now if you are pulling a luma key from footage and want to get rid of black edges, using keyer curves can be the best route, but CG should ALWAYS divide perfectly.  If it doesn't you should send it back to the CG people because something is wrong and you will waste a ton of time trying to fix something that should never come up.

[A_Over_B]

or just don't bother going back and use pixelspread and get the pictures out of the door and be done and go home and...