Merge Node compared to Layer

[masky007]

Hi,

I am transiting from AE to Nuke however i am having some dificulties fully understanding the merge nodes in Nuke.

I know this have been answered couple times now i guess however i couldn't find anything while comparing it to the layers (specificly for the merge nodes)

... its a bit confusing for me atm working with more than 2 or 3 merges- any tips?

Thanks allot

[Andreas.Jablonka]

Hi,

I am transiting from AE to Nuke however i am having some dificulties fully understanding the merge nodes in Nuke.

I know this have been answered couple times now i guess however i couldn't find anything while comparing it to the layers (specificly for the merge nodes)

... its a bit confusing for me atm working with more than 2 or 3 merges- any tips?

Thanks allot

can you be more precise in what is confusing. if you dont know what over,screen, min and max mean maybe consider reading one of the comp bibles out there. this is a typical after effects problem, which makes it way to easy to throw stuff together without knowing what it is really doing.

short answer:
over: A over B (default)
screen: A over B additive (reflections) without consideration of alpha
min = darken : keep lowest pixel value of both input images
max = lighten : keeps highest pixel value of both images
add = plus: A+B

keymix : A over B in areas where the mask channel is 1, ignores incoming alpha of A

[masky007]

Not exactly.. ok i will give you one example...

i have 3 read nodes reading the same image.. every read node followed by transform node (giving them little random rotation and moovment to all so...
Followed by that we have 1 merge node in the middle
i connect the read node 2 to B of the Merge node
i connect the read node 1 to A of the Merge node
and last i connect the read node 3 to A1 of the merge node
so....
Now what i expect is (actually how my mind still thinks trying to match the layer based system like in AE)

First on the very back side should be read node 2 right? cause its connected to the B of the merge
after that on top of read node 2 should come read node 1.. cause it's connected to A and last read node 3 on top cause it's conneted to A1

so now if i select read node 1 and disable it it works normal.. or read node 3 same.. i mean it just disables this image ... ( remember these were connected to A and A1)
Now if i select read node 2 and disable it.. it dosent acts normal to me :P..
with read node 2 disabled on the viewer is shown only read node 1 or (A) but not read node 3 (A2) why lol? i mean i only disable read node 2 i suspect to turn off only that node.. obviously i am not understanding the right idea of the merge node....

question 2

so my example as before.. we have the 3 images overlaping one on another and now i.e. what if i want to crank down the opacity to some of them? how can i do that?

i wish i started learning nuke directly.. this makes my head confused allot i just cant let go of the layered based system yet.. photoshop after effects premiere and whole bucnh of other programs all layere based systems.. thats how my mind works for now ... and i am gonna need some time + help to learn all over with nodes i think

thanks

[sepu]

for your first question can I see some your script ... its pretty easy ... remember that B it is what carries if you have more stuff (more channels, etc)

2. Each merge node have a Mix slider where you can play with your opacity if you want to just apply some opacity to just a single footage add a multiply node which is the same as opacity

[metalrahul]

Like Andreas said, it would be much easier to operate Nuke once you understand how things work under the hood. I recommend you buy this book http://www.amazon.com/Digital-Compos...dp_ob_title_bk

[samzen]

Like Andreas said, it would be much easier to operate Nuke once you understand how things work under the hood. I recommend you buy this book http://www.amazon.com/Digital-Compos...dp_ob_title_bk

also if you are simply looking for transition from nuke to AE there are tutes which ll help you

http://magazine.creativecow.net/arti...-effects-users
http://ae.tutsplus.com/tutorials/wor...ke-ae-premium/

[masky007]

for your first question can I see some your script ... its pretty easy ... remember that B it is what carries if you have more stuff (more channels, etc)

2. Each merge node have a Mix slider where you can play with your opacity if you want to just apply some opacity to just a single footage add a multiply node which is the same as opacity

here it is






2nd question: damn i am blind i tought that was multiplication lol thanks :P

Like Andreas said, it would be much easier to operate Nuke once you understand how things work under the hood. I recommend you buy this book http://www.amazon.com/Digital-Compos...dp_ob_title_bk

Thanks for the recommendation, my friend got this book and he is willing to loan it to me however his DVD was lost/broken - could you send me the dvd so i would spare some money? thanks

also if you are simply looking for transition from nuke to AE there are tutes which ll help you

http://magazine.creativecow.net/arti...-effects-users
http://ae.tutsplus.com/tutorials/wor...ke-ae-premium/

Thank i will have a look at there

[Andreas.Jablonka]

1) the B input carries all data including the FORMAT of the comp, if you remove it most things break. just dont. or plug in a black constant wit the same size.

2) great have fun with the book. no we cannot send you the DVD, can you wash my car? seriously its an odd questions. also you dont really need it anyway.
3) i would use 2 merge nodes and not do the A1 thing. that gives you an easier way of seeing how things are layered and gives you the mix slider to adjust opacity for every read node.

[masky007]

I meant to send the dvd files or something to download it from somwhere :P

Thanks for the info i have been inspecting allot into these things i am starting to get the big picture now.. followed an digital tutors tutorial and i managed to replicate almost everything perfect, now the things are much more clear to me..

this is what iv done (despite is replicated from the tutorial i like it allot :P)

[masky007]

ok i have run into some issue again with the merge (over)

This is a bit confusing..



A read(.tif)
|
M(over)-B read(.jpeg)
|
Viewer

And what i get is someting mixed up, as i used the screen operation compared to AE..
I'v found something on the net about this issue and as they said for the over operation to work correctly, the image going into the A input must be premultiplied with a matte and must have the same matte in the alpha channel.

What i tried is adding premult node after the A read node, it fixed the problem HOWEVER it's not.. the A doesn't show up as foreground at all.. the B is on front

Can someone please explain me why exactly this is happening and fast and sufficient solution.

Thank you

[masky007]

i thin i have foun solution i just enabled auto alpha on the a pipe.. however i am not sure why is this happening any explanations whats really going on?

[Andreas.Jablonka]

please read up on "premultiplication" an over taken a premultiplied image (an image with HAS an alpha channel) and puts it over the image B. if your tif has no alpha channel (press A in the viewer to view the alpha) it wont work.
Auto alpha just adds a solid white alpha channel to a read node that has NO alpha channel in the footage your reading. this also means that the WHOLE image will be on top of image B.

screen (the same as plus) does NOT need an alpha channel, its math just adds image A and Image B over it each other rather than occluding (covering) it.

[masky007]

Zomg andreas thanks! well i have read about premultication earlier however i did not understand it fully - thanks to you i do now.

[Andreas.Jablonka]

its a complicated topic for sure. think of it as adding or removing transparency temporarily to deal with the rgb values only.