View Full Version : Best way of rotoscoping?
December 21st, 2004, 02:50 AM
I was just wondering what the best method for rotoscoping was. Is it adjusting your spline frame by frame? Or do you just take the key poses and let the computer interpolate the frames?
I've just started rotoscoping for the VFX Challenge and even tough I knew it was hard work, I still feel I'm doing something wrong. This frame - by - frame doesn't advance at all. Or am I just a slow rotoscoper?
December 21st, 2004, 03:15 AM
I was actually chatting with someone about rotoscoping techniques yesterday - I'll run through what we were talking about (note: I've never roto'd professionally)
When roto-ing an object, do it in seperate sections (ie, a person's arm seperately from their head) - this stops nasty problems when two sections overlap.
When setting a new keyframe, move the rotoshape as a whole to as close as it can go, and then tweak the points.
Try and keep points at the same position on the object you're roto-ing. (if there's a point that's at the tip of a finger in one frame, it shouldn't be on their wrist in the second)
Try to have a real-time playback of the animation available - keyframe at obvious motion boundaries (example given to me was a person riding a horse - you'd want to initially keyframe just the up and down positions of the rider, and then check how the interpolation looks on the frames between.) - letting the computer interpolate for you will give you much smoother motion than if you did it yourself frame by frame
To answer your actual question, I'd definately suggest letting the computer interpolate frames if it can - watch the video through and decide where you want the roto to be, and then place keyframes at the points where the motion changes. Then check halfway between keyframes to see if it lines up. If it doesn't, add another keyframe there. Once you think you've got enough keyframes, go through it frame by frame and check how it looks.
Thanks to Ian for all the tips above.... (I don't think he comes here, but credit where credit's due...);)
December 21st, 2004, 05:51 AM
Using a tracker also helps when it comes to little movements in a shot. Even if the movement is small it will have a big effect on the end matte if not roto'd corectly. I aggre with all the tips above. Also check out the tips on www.fxguide.com
December 23rd, 2004, 12:29 AM
February 3rd, 2005, 08:13 PM
What about motion blur? Any particular tips on handling that in roto? Like where to lay the boundaries of the inner and outer edges? Thanks.
February 3rd, 2005, 08:34 PM
I tend to use the the solid edge of the object I am trying to roto because when you turn on motion blur for your slpines it tends to give it that extra kick
February 3rd, 2005, 11:47 PM
Tip of the Week #5 (http://www.digitalgypsy.com/vfxlog/archives/2005/01/tip_of_the_week_4.php).. Ugh.. Now I have to figure out what tomorrow's Tip is going to be..
February 4th, 2005, 12:42 AM
ah~ does anyone use mokey to separate BG and FG, as i know it can export separate matters.
February 4th, 2005, 02:16 AM
looks like your question was answered. the only thing i have to add to that is that the best way to get through basic roto is by thinking like a 2d traditional animator. Lay down main keyframes and let the computer do the in-betweening as mentioned above.
as for mokey, i'd be interested to see if anyone has ever used it successfully on their own projects besides the tutorial.
February 4th, 2005, 03:27 AM
Thanks for all the added feedback after that bump to the thread. I guess I didn't word my question quite right.
I know in Shake with a rotoshape node, you can control where the inner/outer or hard/soft edge boundaries lie. My question is where is it appropriate to position the inner and outer edge. With a motionblurred object, is it just a matter of placing the hard edge just where the motionblur starts (least opacity) and placing the soft edge where the motionblur is hardly seen anymore? Or is it better to just use the no soft edge, positioning the spline where the motionblur starts and let motionblur of the roto itself take care of things...
Perhaps I've answered my own question. I hate when that happens...
February 4th, 2005, 12:51 PM
to fiveftaway: i tried the mokey with the V103 challenge footage of the car and successfully export the separate BG,but still need to do some fix to it. and the matte of the car(FG) is really bad,