How to animate a line being drawn?

Hi,

does anyone have any idea how I could go about this? I need to animate a simple wavy line being drawn then erased. It’s simple, but I can’t figure out how to do it.

For the drawn effect, you can create a line like object with extrusions and animate it with the build effect. If the line is straight, you can also try to use a wipe effect on the Video Sequence Editor.

well, you could do curve path and add an particle emitter on it. Then just crank approriate settings on particle life and other settings.

Check out this tutorial, I think it may contain what you are looking for.

http://vrotvrot.com/xoom/tutorials/Welder/Welder.html

Thanx for the replys, but build doesn’t work, because it builds in segments, but I need a continous wavy curve drawn, and I just can’t make it do that. That might be my fault so help is appreciated.

Particles rather fade it in for me, or I don’t understand what you mean :slight_smile:

edit: Just saw Lupus’ post, thanx, if this is what you meant by particle system, that might work, off to try it.

yeah, that was what I ment. I once did small anim where pen wrote text on paper with that technique . Worked pretty well.

Yes, it works, thanx a lot

Ok, I have a new problem. It works, but it becomes segmented, because I need to move it pretty fast, so it moves quite a bit on the curve in one frame, however that one frame becomes a straight line since particles don’t follow the curve, but the movement of the emiter frame by frame. Is there a native way to do this, or do I have to render much more frames and cut it afterwards?

particles shouldn’t have an own velocity at all. so, leave Norm and Rand at zero. as the emitter moves, it siply leaves a trail behind (every particle stays in one place without moving.

what you might change is the keys value and the particle count.

Can’t you use animated textures for this? Someone suggested it to be the most effective method for things like fuses after I described I had used keyframed extrusion along a path curve. I think you just have textures with an alpha channel and animate it. I haven’t done it myself but I have seen animated textures used and they are very effective:

http://homepages.nildram.co.uk/~raytrace/tutorials.html

Animated textures would probably render faster too.

What he means is that when a moving object emits particles, particles emitted between frames are placed along a straight line between the two frame positions, rather than along the curve.

Vis:
http://www.cs.newcastle.edu.au/~c3018900/particles.png
Here, the particle emitter follows the circle, it goes all the way around in 6 frames. Look where the particles end up!

oh - didn’t know that… any solutions, except post-production tricks (like rendering this animation in 60 frames instead of 6 and taking every 10th image?)

What about the build effect?

build effect doesn’t work, or at least I can’t get it to build continously.
I did render more frames then used only a few.