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Jaycee
01-13-2005, 11:08 PM
If you are a Fusion user who also uses Shake, please read on for some help! I am learning Shake and have a Fusion/Combustion background. They actually have a lot of similarities, but there are some tools and tool uses that confuse me. I have a list of tools that I believe correspond from package to package, but then several more that I have no idea what the deal is.



Fusion/Shake


Merge tool: a compositing tool for putting one layer over another with different modes/ The layer tool…except when you sometimes want to use the “keymix tool” which is a bit nebulous for me still.



The brightness contrast tool: a tool I often use on alphas to set them to white or black. I have no idea what tools you use in shake to manipulate the alphas including inverting it, making it all black, all white, or all black except a designated area through roto splines, or expand and shrink them.



The bitmap option in fusion/ does this correlate to the m option for mask in Shake? And what about the “switchmatte”, what is its function or purpose? Oh and while we are on the subject of masking, how come it says you shouldn’t use your quickmatte roto on more than one tool?



No idea/imult Idivide…used for dealing with rgba premultiplication problems…do you really have to use this on every rgba layer you bring in that needs color correction?



The color corrector/what do people in shake use for color correction predominantly? I am told you use imult, compression, and all sorts of other odd methods of color correction but I’m interested in the one that gives you control over gamma, gain, curves, histogram, just like a discreet package I guess.



Loader/FileIn node: it all works except the alpha layer shows up black on Shake for some reason? Is black the default alpha and why would this be so? Black is normally transparent, right??



That’s all I can think of right now, but I guess I just wanted to get the thread started to see if I’d get any bites. Thanks in advance!

Hugh
01-14-2005, 10:20 AM
Before I start - black on dark grey is a little painful to read......

I'll see what I can do - I don't use Fusion all that much, but from your descriptions, I think I can help....

Merge tool: a compositing tool for putting one layer over another with different modes/ The layer tool…except when you sometimes want to use the “keymix tool” which is a bit nebulous for me still.

The Layer node is a hold-all for the different types of layering - I'll usually use the Over node (or Under, which is Over with the inputs reversed). You're also got IAdd, IMult, Max, all of which are very useful.

The brightness contrast tool: a tool I often use on alphas to set them to white or black. I have no idea what tools you use in shake to manipulate the alphas including inverting it, making it all black, all white, or all black except a designated area through roto splines, or expand and shrink them.

Most of the tools in the colour tab can be told to only affect specific channels. So, for example, if you want to invert the alpha, use an Invert node, and set the channels parameter to "a". To set the alpha to something specific, use the (aptly named) SetAlpha node. (There's also the Set node, that you can use to set any of the channels in the same way as SetAlpha, but with the channels parameter)

The bitmap option in fusion/ does this correlate to the m option for mask in Shake? And what about the “switchmatte”, what is its function or purpose? Oh and while we are on the subject of masking, how come it says you shouldn’t use your quickmatte roto on more than one tool?

The "M" input to nodes in Shake defines where this node will affect. If you want to cut out everything except a certain area, the Inside node is the one you want (or the opposite with the Outside node).

As for using the quickmatte roto on more than one tool, I'll explain what I think they're talking about....

Take a look at the following three groups of nodes:

http://www.brokenpipefilms.com/hugh/images/mask_concat.jpg

The one on the left is a good example of concatenation of nodes. If you were to look at the three nodes under the ColorWheel in the tool box, you'd see a little yellow 'c' in the top left corner. This means that they will concatenate. This is when, internally, it actually treats them all as one node, so it's a lot faster to process. Internally, the tree on the left will be a ColorWheel node followed by a Lookup node (that is set up to do the same as those three nodes).
However, using the mask input breaks concatenation. The second example is an example of this - each of those nodes will be treated seperately, because Shake is thinking that they will each be affecting different areas of the tree. This is bad.
The third example is how to fix this. In this one, the three nodes concatenate, and then are made to only affect a part of the image by using the KeyMix node at the end.

Oh, and SwitchMatte is a node that takes the rgb channels from one input and the alpha from the other input. It gives the option of which channel from the second input to use as the alpha, and also whether you want to multiply by it.

No idea/imult Idivide…used for dealing with rgba premultiplication problems…do you really have to use this on every rgba layer you bring in that needs color correction?

I think you're thinking of MMult and MDiv. These divide by the matte (alpha). IMult and IDiv will multiply/divide by another image.
When you're colour correcting an image that's already been multiplied by it's alpha (rendered CG, for example), you should put an MDiv on before doing any colour correction. This will give you quite bright edges where the alpha is between 0 and 1, but it will stop these looking wrong when you actually comp it over the background. After doing the colour correction, you should MMult again to give it back the nicer edges.


The color corrector/what do people in shake use for color correction predominantly? I am told you use imult, compression, and all sorts of other odd methods of color correction but I’m interested in the one that gives you control over gamma, gain, curves, histogram, just like a discreet package I guess.

Depends..... If you're colour correcting in log space, then you should be using Add nodes only... If you're in Linear, then you can use pretty much anything except Add nodes... I'm not sure what I'd use in Linear, as most of the work I've done has been in log.


Loader/FileIn node: it all works except the alpha layer shows up black on Shake for some reason? Is black the default alpha and why would this be so? Black is normally transparent, right??

You're right, and this does kinda annoy me at times. Turn on AutoAlpha in the FileIn to make the alpha white on a FileIn that doesn't have an alpha already.

This can be useful, though - I find that if I'm comping CG onto background, I'll leave the background with an alpha of 0. (It's not been multiplied by it's alpha, which is why there's still colour there - it's best to think of alpha as a seperate channel rather than the transparency of the image) - This means that, at the end, I've got my comped image where the CG has an alpha of 1, and the background has an alpha of 0. With this, I can use the alpha channel to decide where I need to add grain to.


That’s all I can think of right now, but I guess I just wanted to get the thread started to see if I’d get any bites. Thanks in advance!


Well, I hope I've been of some use.... As I said, I've not used Fusion that much, so I'm just kinda going by your descriptions....

Jaycee
01-14-2005, 06:30 PM
Thanks for such a detailed reply, Hugh! I think that clarifies everything a lot better. Shake is very touchy about using the right nodes in the right context, but once you do it seems it runs very quickly and u can use a lot of creativity with it. If I think of anything else I will write again, but I think that helped clarify things. THANKS AGAIN!!!

Aneks
01-15-2005, 07:22 AM
I have used fusion a little so maybe I can add a little to what hugh wrote :

THe merge tool. In a big comp I want to look at my layering ooperations and know right away what they are doing. For this reason I never use the 'layer' node unless I am using some fancy photoshop style transfer mode and then I will rename the node. Use the correct type of layer for the operation you are doing ie over, add, inside etc
One thing that shits me and attracts me to fusion is the merge node. When I screen something over a layer I want a screen node not a bunch of dropdowns and sliders


The color corrector/what do people in shake use for color correction predominantly? I am told you use imult, compression, and all sorts of other odd methods of color correction but I’m interested in the one that gives you control over gamma, gain, curves, histogram, just like a discreet package I guess.


you mean other than the color correct node ? :)

Once you get used to it i think you will find that colour correction should be dealt with in a more simplified manner. Color correct (love that spelling) is actually a macro that combines nearly all the other colour nodes in one.

A total shake guru once showed me a tree he made which had only one colour node : expand. Ever since than I have become quite fond of expand as it allows for luminance, chrominance and alpha manipulation all in the one node !

So in answer to your other question i recommend using expand to maniplate alphas

No idea/imult Idivide…used for dealing with rgba premultiplication problems…do you really have to use this on every rgba layer you bring in that needs color correction?

iMult and iDiv are rad nodes. Used them for logical operations on images and mattes, although min and max are better for matte booleans. Have a look at my multipass comp or ambient occlusion comp tut on vfxtalk.com to see how I use these nodes everytime I comp ...

The bitmap option in fusion/ does this correlate to the m option for mask in Shake? And what about the “switchmatte”, what is its function or purpose? Oh and while we are on the subject of masking, how come it says you shouldn’t use your quickmatte roto on more than one tool?

There is a reason why fusion 5 has a seperate matte tool and hugh has demonstrated it. The bitmap option seems fun but it can be deadly. Dont think that way anymore keymix is our friend..... so to switch matte it keeps me warm at night with its brilliant ability to take the rgb channels from one input and use any channel from the second input as the matte for that layer.............. joy !!!

also anyhting with the name 'quick' like quickmatte or quick paint should be treated with extreme suspicion. Use rotomattes....

Hugh
01-17-2005, 10:40 AM
Since Aneks has mentioned QuickPaint, I feel obliged to point you at a post over at VFXTalk that I wrote last week on what to do if a node starts crashing Shake.....

This (http://www.vfxtalk.com/forum/showthread.php?t=3450) is the post in question.... I'd definately recommend anyone doing intensive stuff with Shake to read it...

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