Light Trail

#1

I’m trying to get the effect of a light trail behind an object, like the bikes in Akira. I’ve tried motion blur, but creates blur in front of and behind the object when I only want it behind. Any ideas?

#2

Originally posted by Fasty
I’m trying to get the effect of a light trail behind an object, like the bikes in Akira. I’ve tried motion blur, but creates blur in front of and behind the object when I only want it behind. Any ideas?

Adrian van der Park developed an excellent technique for this effect back in 1998, using geometry for the light trails and Lazy Points (now known as the “Inertia” plug-in in the Deformations tab in the Object Properties panel) to make the geometry stretch along the path of the object’s motion.

I’ll see if I can whip up a quick and dirty test…

#3

Thanks Celshader, that would be awesome if you could! I remember that tut I think, but haven’t been able to find it.

#4

Yeah – I remember that technique – used it once myself.

Make like a guitar pick shape that’s dimensional, and use lazypoints, err, I mean inertia, to drag it around.

Works really cool – you’ll understand more when Cellshader comes back with the example.

#5

Ok I used Inertia and got an ok effect. With tweaking I’m sure you could get it looking nicer, and more like Akira light trails. Looking forward to Celshader’s results…

#6

For what it’s worth:

You can see a bigger version here:

This is not the “guitar pick” object that Adrian van der Park used for his Trails of Light tutorial back in 1999, but it still uses his idea of applying LazyPoints/Inertia to geometry for a “light trail” effect. I took advantage of the modern LightWave’s weight maps for this effect.

Trivia:[ul]
[li]On each object, I used the same weight map to both surface the object and to control its animation in Inertia.
[/li][li]I used Glow on both light trails.
[/li][li]Each light trail is a box with a slightly tapered end, so that the trailing end appears reduced in size. Each light trail box has 100 segments along its Z axis, and has been tripled to reduce the chances of distortion.
[/li][li]These surfaces are not transparent. They have Additive Transparency cranked up to 100% instead.
[/li][li]Each light trail’s surface has a Constant Value of 128 for its Alpha Channel. That way, the glow of objects behind the “light trail” can still be seen through the “light trail.”
[/li][li]I put an envelope on Inertia’s lag so that it has no lag at the beginning of the animation and its full lag rate by frame 12 – that way its trailing end stays “soft” even at the beginning of the animation.
[/li][/ul]

I hope this helps! :slight_smile:

#7

Celshader, that is an awesome help, though is it possible to take a look at the scene files if you do not mind?

#8

Thanks for the breakdown on that effect.:applause:

It’s always fun to see how others use LW in ways other than what I tend to use it for.:thumbsup:

#9

Thats a cool effect I’ld like to learn. To bad I don’t understand half of your instructions :slight_smile: only cause I’m sadly lacking in skills.

I too would appreciate a peak at the scene file if that would be o.k.?

#10

Great work Celshader. Thanks for the R&D :slight_smile:

Fasty I really like what you’ve got there though. I think the streaks on the trails created by the star shapes works really well.

#11

can u, celshader, please, pretty please write a tutorial.
i think a lot of people will be happy
thanx a lot
:applause:

#12

OK Jen, you just keep me rocking. I so can’t wait to go home and try that effect.
Man, thats cool and so utterly simple (I hope).:applause:

#13

Hey Jen,
After printing this thread out so I could try it home, that tut you mentioned sounded familiar so I went out to your site and sure enough you have a reference to it but the link to his site is dead. Do you have a copy of his tut or better yet are you going to write a quick tut?

#14

:love: Jen you are my hero. That’s brilliant, exactly the effect I referring to! I hope you seriously consider writing a book at some stage, because I for one wouldn’t hesitate buying it.

#15

I made the box, used taper made a weight map and changed the end to be at 0. add a nice gradiant and brought it into layout. There I ran into trouble

How do I get it to orient to the direction of movement? Do I have to hand do it or is there a way to have it follow a null or something?

Also is there a easier way than cutting the box up with the knife to get the weight map right? Couldn’t figure out how to apply a weight map with the blend that was mentioned otherwise.

Jay

#16

Under the objects motion options you can make the object “align to path” or something similar. As for dividing the object up, try Bandsaw.

#17

Originally posted by sketchyjay
[B]I made the box, used taper made a weight map and changed the end to be at 0. add a nice gradiant and brought it into layout. There I ran into trouble

How do I get it to orient to the direction of movement? [/B]

Fasty nailed it – I used Align to Path for this animation. The box must be aligned along the Z axis in Modeler for this to work.

Originally posted by sketchyjay
Also is there a easier way than cutting the box up with the knife to get the weight map right? Couldn’t figure out how to apply a weight map with the blend that was mentioned otherwise.

I started with a box that had 100 segments along the Z axis. I then created a new weight map with a value of 0, so that I had a “blank canvas” on which to paint my weights.

The secret to a gradient falloff of weights is the “Linear” option in the Weights tool’s numeric panel. After activating the “Linear” option in the numeric panel, I used the right mouse button to click and drag out a falloff triangle (just like the falloff triangle for the Taper tool). When the falloff triangle looked the way I wanted it to look, I went back to the numeric panel and set “Change” to 100% and clicked on “Apply” to apply the weights. If the weights looked wrong, I typed u to Undo the Weights tool, adjusted the falloff triangle and tried again.

Originally posted by aurora
…are you going to write a quick tut?

I’ll see what I can do. :slight_smile:

Originally posted by Fasty
I hope you seriously consider writing a book at some stage, because I for one wouldn’t hesitate buying it.

Thanks! :cool: For what it’s worth, check out LightWave Applied, version 6.5 & 7 if you have not yet had a chance to do so. I wrote three tutorials for that book. One appears in the book as the “Character Setup” chapter. Another appears on the CD-ROM as a “Spline Basics” tutorial. The biggest one appears on the book’s bonus website for readers:
http://www.advanstarbooks.com/lightwave/bonusaccess.html

“Character Modeling and the Super Cel Shader” has 717 explicit steps and 462 illustrations showing the reader how to build a celshaded elf-girl from scratch. I have a preview of its table of contents here:
http://www.celshader.com/gallery/kara/contents.htm

…and an excerpt of it here:
http://www.celshader.com/gallery/kara/contents.htm

:slight_smile:

#18

Celshader, you are a credit to the Lightwave community! :beer:

#19

I tried yor tech out last night Jen and managed to get it to work except for the weight mapping. I came into work to ask for help and Bam you already answered my question. Thanks for all the info!
For others I used something other then a box so what I did was create my ends with non-divided center, cut that center to a new layer, used juliene slicing on it cut and pasted it back to the original layer merged points and went from there. Worked fine for me.

#20

Align to path did it.

I had the end of it going out along the +Z side instead of the -Z side.

I had to shrink the box to an inch long to get all of it to show up. anything less than 4 meters/sec causes it to flutter more like a ribben in flowing water rather than like light following a trail.

here is my test
ray of light

thanks Celshader, this is something i’ve been trying to do for a while.

Jay