View Full Version : Need help pulling a matte

10 October 2005, 03:46 AM
Hey guys,

I have a picture where I want to do a sky replacement. I did a lumakey on it but I cant figure out how to treat the matte. take a look at this pictures:

node tree:


I'm pretty sure that the best way to get a good matte is to key the trees and the church separately. what suggestions do you guys have that could help me?

Thanks in advanced!

10 October 2005, 10:39 AM
Try The Keylight or isolates some channels to create a matte. You can use rotoshapes for isolate the action of Keyers (Plug the rotoshapes in the "Mask" Input)

10 October 2005, 02:08 AM
i tried using the blue channel to key the sky out. the promblem that i have now is tryin to choke the matte, i've tried using the dilateErode node but I didnt get good results. the brances have have a big matte ouline around them.

how can I shrink the matte without havin the branches dissapear?

thanx for the suggestion Vympel

10 October 2005, 03:40 AM
*edit* sorry didnt see your last post.

Could you not shrink the matte then try and extend the edges with an emboss or convolve? And maybe also try not eroding so much and take care of the rest with a slight blur? I know the dilate erode has a softness but alot of times the blur after the erode seems to work better for me.

10 October 2005, 04:15 AM
Used the Keylight? Before applying the Blur and/or erode/dilate. Made some color correction (expand, add, color replace for example)?

10 October 2005, 06:17 PM
thanks for your replys guys!

to pull the matte i decied to do a conversion of color space from rgb to yuv and used a dilatederode with smooth on to shrik the matte. it kinda worked but now i have a line from my rotoshapes that i cant get rid off.


node tree :

I also did a color correction. Please let me know how is comin together


10 October 2005, 10:16 PM
you can dilate/erode your rotoshapes smoothness, cant remember the term but you can change the falloff of your rotoshape, also you can blur the rotoshape. All that I think should get rid of the hard lines.

I think messing with the falloff is your best bet. Im no professional though.

10 October 2005, 02:02 PM
Rotoshapes in Shake it has variable fallof ( edge mode),using this way you really make use of a bigger control of fallof. When I spoke of color correction, was relating me the creation of mattes, comings of channels of the original image, increasing contrast, scaling matte for example

10 October 2005, 03:22 PM
You could try using Primatte...
Use the Spill Sponge and/or the fine tuning to work on the branches. I find it to be pretty good at fixing whispy stuff. The luma matte path creates a more chunky matte IMHO.

Probably a good combination of blur and a touch of dilate erode, a balance you will find by experimenting, will do the trick.

Did you check the macro on HighEnd3D called "SpillReplace1"?
It did a great job on some tough spill I had on a key yesterday.

10 October 2005, 06:27 AM
thanks rurik, i'll download that macro tomorrow!

11 November 2005, 06:30 AM
hey guys, here's an update!

i finally figured out how to pull a good matte to comp the clouds in. I added some leaves falling to give the shot more life. theres a mistake with the leaves, theres a couple at the end that pop in and I will fix that rite now. I also added a camera shake, which still needs some work. I want it to have the effect of hand held camera. Anyone has anytips on how to achieve this?

I would also like to remove the grain from the pictures by bluring each channel seperately, but im not sure how to combine all 3 of them back together. any ideas?

Let me know what you think! comments and suggestions are more than welcome!

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