Forum Replies Created
-
Posts
-
Hi there.
Are you sure, you want to do it that way? General speaking, it doesn’t matter what process you use, channel manipulation, using a designated “keyer”, rotoscoping, or whatnot, what count at the end is that you have a good matte to separate your fg-object from your bg/green-/bluescreen. I hope you don’t mind if I start with some basics (the way you phrased your question leads me to the assumption that you just started out with combustion and/or compositing).
Ok. Color images can be represented by a number of color spaces. One of them is the RGB color space. The color captured is split into three color channels: red,green and blue. Each of these channels can be thought of as either a picture with shades of the respective channel, or as a black and white (grey scale) image. if you use the short-key “ctrl+shift+5” the red channel of your viewport image will be displayed. “…+6” is the green channel and “…+7” is the blue channel. Each channel as a grey scale image.
the following is a coarse description of the process. if you have difficulties following it, it’s either i have some trouble finding the right words, or you’d better do the tutorials which are shipped with combustion.
Say you have a green-screen shot. load that in a viewport and look at the green channel. you’ll see that the bg is almost white and the fg almost black, or at least a dark grey (maybe except from highlights on the fg object). what you try to achieve is a black bg and a white fg. so, you inverse the image. since you want to have a solid black bg, you can either add an histogram-op or a curve-op. manipulate the green channel until you get your wanted result. use a compound alpha arithmetic op. for the main input of that operator use the original footage. as secondary input use the manipulated one. in the controls of that op set operator to “set” and input to “green”. the result of all that should be a more or less (more likely) good key of your original footage.
this is, all in all, the concept of a (very basic) chroma keyer.
a more evolved technique is that you determine which of the original red and blue channel is brighter and take only the brighter pixel for further proceeding (take a look at the compound rgb arithmetic op) and subtract those from the pixel in the green channel. of course the result of the subtraction, as well as, each channel prior any operation can be scaled using curve- or histogram-ops. this later concept is the one which is behind a color-difference keyer.
you might want to read steve wrights book “digital compositing for film and video” (focal press).actually, it’s 3dsmax that doesn’t render the z-depth channel as you would expect. when rendering the z-depth pass it does so by using the geometry properties and not the material. only way to overcome this situation, i know of, is what einstein suggested. using a 100% white material and black fog.
best,
-raykhi,
actually, the graphic card performance as a whole is not that important for the performance of combustion (as of version 4; you never know what the future will bring, but then, you’ll buy a new computer anyway). the only part of combustion which is accelerated by the gpu is the particle op. if you do a lot with particles, a high-end graphic card will help you. if you work in opengl mode, the transforms of layers aren’t cached but rendered by the gpu just in time. the backdraw is, you don’t have all layer transfer modes.
imho, max out the system ram, then buy the fastes cpu which fits in your budget and then think about the praphic card. here, i would tend to look first at graphic ram and then at the gpu.
keep in mind that this is just my opinion regarding stuffing a system to run smooh with combustion. if you have on the same system other software, aspecially 3d software, the balance of parts in your system may shift towards more importance of a good graphic card.cheers!
-rayknot much you can do, use some noise to hide the banding, or use a 10bit codec.
-rayk
file -> export … -> choose “.ase” for file format, insert file name, push the save button, dialoge appears, go on from there…
best,
-rayki could get away with using the standart tools of combustion with good results so far. but i have to admitt that it needed alot of selections and tweeking sometimes. as someone wrote in another forum, using additional (3rd party) keyer, just broaden your options to get a good key fast. it’s like one keyer plug-in will work on one shoot and fail on another. or it will give good results in one area of the image and you better use other tools for other parts.
best,
raykhi again,
i may misunderstand you … so sorry, if the answer is off-question…
when you create a controler and link it to a specific channel, you create an expression which simply says put the value (you specify in the controler) in the channel you picked (to be controled). that’s a one way. so, if you change the controler value, the controled channel value should change accordingly. the other way around doesn’t work.best,
-raykhi light,
you might want to use a merge-op instead of the comp-op, then feed the output of the merge-op into a comp-op. if you want to make a capsule out of this then, select everything but the footage-op, comp-op and layer-node.
should work then.-rayk
… don’t know, i can render out wmv 9 files.
maybe you need to reinstall combustion after you installed the codec?-rayk
well, there would be a kind of hack (isn’t there always 😉 ).
but first off, doing it inside 3dsmax might be the fastest thing to do.
ok, back to topic. the ase import can only import camera data. that said, all your “planes” you want to animate in c* would translate to animated cameras inside 3dsmax. once you animated all those cameras in 3dsmax, export an ase file. inside c* create as many 3d-composites as you have cameras. no footage or layers needed inside these comps. in each comp select the camera and import the appropriate 3dsmax camera from the ase file. go to your “master” comp with all your layers you wants to animate and link the layers transforms to the cameras transforms. that’s it 🙂
a lot of hassle, not worth imho.good luck,
-raykyeah, a lot of people seems to hope for a sdk for combustion. currently, there’s no sdk for c* and if there ever will be one, time will tell.
cheers,
rayki’d go with a tablet, just because it is cheaper and you still have all the power of your workstation.
-rayk
no, i don’t think so.
as a side note, in case you don’t use a tablet, you should. it will speed things up a bit, too.-rayk
… not really scripting, but you can use expression. some are unique for combustion purposes, but mast are based on javascript. help files are a starter, then look at javascript and experiment.
best,
-raykhey mike,
you already placed your orders, don’t you? 😉
do you guys from fxphd think you can get your hands on a “beta” and post some test shots, asap? since we are on an fx site, green- and bluescreen footage with some fast moving fg would be great. 🙂thumbs up (is this still the appropriate term?) for your fxphd project.
cheers!
rayk