View Full Version : stick newbie -- please help!

05 May 2011, 05:14 PM
I'm a newbie to Nuke who needs to finish a class project. I realise these will be really basic questions & you may well be tempted to tell me to go and watch some basic tutorials; the fact of the matter is I've spent the last fortnight doing nothing but Nuke and watching tutorials on digital tutors, foundry channel on youtube etc. but I still can't grasp roto-ing, alphas, keying, anything! I follow the tutorials, and it seems to make sense and the techniques work on the project files.. but once i try using my own footage nothing works, or if it does eventually work I don't understand why, so consequently I can't transfer anything to a new problem.
Most of the tut's don't cover basic stuff, or they're some guy mumbling into the mic whilst clicking around trying to comp a specific scene - there's nothing to tell you what keyers to use when or what a n alpha is other than black=transparent. i don't grasp what all this premult and rgba.alpha is (ie. whats the difference between rgba and rgba.alpha..?)
Are alpha channels specific to one image, or can they operate on a number of images (ie. can I have a 'hole' in the middle of the scene, and have that hole cut through two or more images layed over each other? or do i have to assign the alpha 'hole' to both images. if the latter is so, what if I already have an alpha on that image, how do i keep the two separate?
In my frustration, I've tried to do a simple comp with a grass field as a bg, a car cut from a street scene over that, with a figure shot against a greenscreen for the fg. with the car moving across the field and behind the figure... and i can't even do that. I've fluked the roto round the car, and animating it across the field was easy. but i can't key the greenscreen. I just don't understand the principles of the rgba, the mask pipes, premults... I just don't get it!
I desperately need a helping hand on a few basic questions, the tutor in class was an industry guy - the lessons were ok when he was there and telling you what to click when things weren't right, but he's gone now so I've got no help to finish this comp. help!!

i understand this seems like a garbled rant but I'm running out of time and options and it's driving me insane!!


05 May 2011, 09:24 AM
there are a lot of basics covered in the nuke manuals.
especially keying is even done with small tutorials. (nuke 6.2v4 docs page 260ff)
in the tutorials section they are covered even closer. (pages 762ff)

after reading them you should really be able to create a simple greenscreen key.

if you encounter such basic problems i would recommend reading the manuals right from the start and keep away from online tutorials that cover stuff for/from professionals.




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05 May 2011, 09:24 AM
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