Compositing-blur Edges

[user_deleted]

hi, people.
Im a new shake user version4.. Im having problems with compositing.. The Problem is i used keylight for keying but the edge of it is too sharp.. I wanted to soften it but the shake tutorial book said you have to make a roto shape and then animate the roto shape.. I believe there is an easier way to blur just the edge of the footage, like what disreet combustion can make.. Now my question is, does someone here knows how to blur edge of the footage without making a rotoshape? Thanks in advance

[user_deleted]

HI!

Try to make a hard key with primatte or keylight which u plug in as a hold-out in a softer key.

I used the alpha edge-erode macro found on this site for my last edge problem, pulled an alpha of the edge of my pretty hard primattekey, did a swith matte with the same primatte, applied some blur and placed it over my primatte

//

[user_deleted]

use keyight to get the alpha mask (but dont composite inside keylight).. then use a blur (and dilate/erode if needed) on the alpha and use a keymix to combine the FG and BG with the generated alpha.

++ c.

[user_deleted]

zem,

wondering why you say not to do the comp inside keylight. i agree with not doing the comp in the keylight you use to pull the key but i do recommend comping the shot in a second keylight. if you dilate/erode the matte and then blur you or going to lose information on the edge. your solution won't work if you have fine hair you are dealing with.

[user_deleted]

well, i just prefer to keep the alpha channel (which of course can be several keys plus rotos combined) seperate from the compositing process.. this way you can work on each element seperately. i usually use a keymix in the end to combine everything.
++ christoph

[user_deleted]

Hi super Morty!
How do you mean, tha you comp in a second keylight? The first keylight is only a rough key, and you key that a second time? I'm really interested in that, can you explain this?
Thanks
Gabor

[user_deleted]

it basically means that you make a hard key first, with really solid matte, but choppy edges, then make this a bit smaller to keep the edges clear, then blur it a bit, and use that matte as a holdout matte for a much softer key which would have holes in it if you would use it alone. basically it's an animated holdout matte. note that you can make a garbage matte by using a similair technique if you have a really uneven screen.

++ christoph ++

[deke-kincaid]

Before Shake 4.0, the keyers only supported 8-10 bits of info, so many of us are still used to doing all the comp outside the keyer and only using it to generate a matte. Shake 4.0 added float support to both Primatte and Keylight.

[user_deleted]

Here's a nifty technique if all you want to do is play with the edge.

Make two keys a hard key (I suggest primatte) and a soft key (I suggest keylight).
With your hard key dilate erode, reorder to alpha only. Now you want to put that into a edge detect which will detect the edges of your alpha only. Blur those edge a little and isub your reorder from your new blur edge node. Switch matte back from your dilate erode. On your softkey, blur than put that into an over (bg) with your new switchmatte (fg).

This is also good if you need to do some spill suppression around the edge as it will only affect the edge. To do this you would just not do the reorder.