By dvhouw
#374063
Hi everyone.
I'm trying to explore the possibilties to create (stock) light trails that can be used for compositing purposes.
The effect I'm after looks like this great image from Mihai Iliuta on the Maxwell v3 features website:


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I've done some tests in Maya, with creating a stick with multiple emitters and moving/rotating it before the camera with a low shutter speed and motion blur enabled.
But as you can see the results are not good at all.


Image

The idea for making a "stick" with multiple emitters came from this interesting kickstarter project:
http://www.kickstarter.com/projects/bit ... ng-evolved

If there's someone who has some experience with this or idea/techniques to try out, it would be much appreciated!

Cheers,
Dario
User avatar
By Mihai
#374079
That's it but as Brian says you need more motion blur steps. Check the Maya docs for details.

One important tip is that you will get MUCH faster render times if you don't show the emitter directly and instead show a surface that's illuminated by an emitter, and this emitter is hidden to camera. I mean that it works of course by showing just the emitter directly, but the light trail it creates will be noise free a lot slower than the rest of the scene.

Secondly, if you need long light trails like that don't use the rotary shutter option since then the longest trail that you will be able to get will be limited by the frames/second in your animation. Use instead the shutter speed as you would normally, just set it at a very lower value like 1, for a 1 second exposure.

I'll have to do maybe a video tutorial about that scene later....
User avatar
By Bubbaloo
#374083
Mihai wrote:One important tip is that you will get MUCH faster render times if you don't show the emitter directly and instead show a surface that's illuminated by an emitter, and this emitter is hidden to camera. I mean that it works of course by showing just the emitter directly, but the light trail it creates will be noise free a lot slower than the rest of the scene.
Great tip!
By dvhouw
#374141
Thank you guys for your helpful comments!
I'll do some testing with more motion blur steps. Also lighting a surface instead of directly looking at the emitter (if I understood it correctly).
I'll post more test images soon.
cheers
By dvhouw
#374686
I've tried some different things which you can see below.
The objects has standard rough materials and were being lit by plane emitters.
The final tests (red trails) were created with a cylinder textured with stripes (see image) that moved along a curve in Maya or with a stack of colored spheres.
The objects had normal rough materials and were being lit by plane emitters.

As a first test run I wanted to replicate the style of trails shown in the coca cola advertising image.
I'm guessing that a there's also a lot a post production involved to get those different colors, contrast and intensity,
so I'm trying to get the best "start/base" trail from CGI that can be further enhanced in post.

Like with photography, the shape and color of the moving objects itself determine a lot how a light trail looks (apart from the movement itself).
So I'm curious what kind of geometry shapes/textures you guys use to create your trails.
Any advice is welcome, thanks!

PS.@ Mihai:
Sample level 25 still has some noise in in the image. Is this way: Lighting in this case a cylinder with a separate light, instead of the cylinder being the emitter itself the technique you described?



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User avatar
By Mihai
#374760
I didn't really mean like that though and it looks like this is not so efficient (these huge emitters illuminating a tiny object - less chance of rays finding object, finding the camera so you see something). I ment parent a small emitter roughly the same size as the object, to the object, so it's a few cm from it. This way you also have a lot more control over the look of the illumination on the object (for example you can animate the small emitter parented to the object, rotate it around the object etc.).
By dvhouw
#374762
Ah alright now I know what you mean, thanks! Makes a lot more sense now.
I'll do some more test runs this week, I'd like to create trails like this..

Image

Any suggestions are welcome.
Cheers
By dvhouw
#375300
After some more trials, I decided to create these trails with different software (I'm using Flame Painter now).
It's really fun in Maxwell but I'm having trouble creating really specific results without spending lot's of hours.
Thanks for the comments, and if there will be a tutorial about the subject in the future, I'd be very interested!
Cheers

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