View Full Version : HELP_Tiretracks in the sand

04-16-2012, 08:27 PM
Hey guys!
I'm doing a scene where the camera does a flyby, looking down on some chariots and horses. What I'd really like is for the wheels to make some tracks in the sand. The problem is, the chariots are clones, so there's no real geometry involved. I'm using HD Instance in LW 9.6. If there's anyone that has any ideas on how to make this work, I could really use the help. thanks

04-16-2012, 09:30 PM
I know how to make tracks in the sand but not sure how to handle it with instances. I would think that if you could get an instance ID it might be possible to parent to it using an expression?

04-16-2012, 11:09 PM
Man its good to hear from you!! I don't know how I'd do that, since I don't know what an instancing ID is, but I can look it up and find out. In any event, I have to say, its just good to know you're ok, :thumbsup: Thanks and take care, hope to hear from you again soon.

04-16-2012, 11:24 PM
That was old stuff in age old LW demos, it was the Hummer in the desert I guess.
Would be cool to see it.

04-16-2012, 11:47 PM
Hey Jimi!
I was asking around if there was a way to parent something to an instance. I was told that its not possible but was also told that if an object is parented to a null and that is instanced youll get multiple nulls which should be able to be referenced. If you can do that its possible to create the tracks using a procedural texture like the marker pen plugin that comes with DPKit.

04-17-2012, 12:35 AM
Larry Dude My hero no make that my super hero. Really glad to see you back on the sight. I hope all is well. I read something today about LW11 being able to use nulls with instances. This was for LW11.1 however not 9.6. I hope that helps. You might also want to look into DP nstance because Denis has done several upgrades to that as over the last few months.

04-17-2012, 06:20 AM
OK, thanks. I also thought about using the pen tool, but I had a failure of a time trying to use it before, with a bug in the sand. I needed some footprints in the desert sand, but the pen tool just wouldn't work for me. That was a while ago. Unfortunately, these chariots are instanced using polygons. I could do set the whole thing up with nulls, so I'll give that a try. thanks guys.

04-17-2012, 06:43 AM
If your sand is flat, could you add a tyre-track polygon that starts at the wheel and stretches backwards, with a semi-transparent tyre-tread texture applied to it. Then add a grid procedural as an alpha, which moves over time (assuming gradients tied to an object within an instance doesn't work - though I've never tried it). A really big grid will give you a black and white surface big enough to not look like a grid when lined up correctly.

This does assume your chariots are all travelling at the same speed though.

Any reason why this wouldn't work?

04-17-2012, 06:52 AM
How do you determine where the clones go?

04-17-2012, 08:10 AM
hi, clone your object, but make it low-poly, make it follow the instance, then use this technique...


(edit: basically what Larry said)

04-17-2012, 08:19 AM
Have a look at the youtube video and content at the bottom of this page:

(it says "mud" but it might be useful for sand) and sorry, i'm not sure about the instancing just the effect of the tracks.
Hope it helps :)

04-17-2012, 08:31 AM
low-res clones will be needed,
yep, Jennifer's ClothFX tutorial/preview should be good too (though rendertimes will be high)

04-17-2012, 11:01 PM
This may be WAY too simple a solution for you, but depending on how close your camera is going to get to the tracks, you can use a technique that I've done several times. It's certainly nothing as elegant as the previous suggestions. Basically I create two landscape images, one which includes the final tracks already drawn out (I've created some brushes I use regularly for this). I start by creating a series of still images in layout from the TOP view of the area where the tracks would be. Make sure you can see your objects at several key points. In Photoshop I combine these reference stills until I can trace out a nice thick line that I check by importing this test landscape back into LW. When I've got one that matches the movement of the objects, I create the second landscape with tracks by using the reference line. In layout you render out both versions (remembering to cast the same shadows both times), then a very simple garbage matte in compositing lets you reveal the tracks as the objects move. There's a scene about 2:45 into this short film that has an obvious example of what it looks like.

04-17-2012, 11:27 PM
Hey Jimi!
I was asking around if there was a way to parent something to an instance. .....
Larry, nice to see you back on the forums. :thumbsup:

04-18-2012, 11:26 AM
I was thinking, you could use this technique for the wheel trails: http://www.youtube.com/watch?v=Z7ycSgLV3mo

Then as mentioned above, use your compositor (AE, Fusion, etc.) to bring the various trails together.

04-18-2012, 04:23 PM
Hey Jimi, how many chariots will there be in your shot?

04-20-2012, 12:29 PM
Man, my heart skipped a beat when I saw you on the forum!:dance: Welcome back to Narnia man!!! OK, let me get a grip. :screwy: Here's the scene render from the wide camera shot angle. I guestimate there's maybe 600 chariots here. But for the overhead cam shot, I may only have about 25 or 30. I think I see where you're going Larry. If I just use the 20 or so chariots, I can mechanically do the tracks in the sand. I think that would be best. As for the other shots, I can just paint something on them in post. That might be the more cost effective way to handle this, since time really is of the essence.

04-20-2012, 12:56 PM
That landscape.... looks like Yakima. >;^)

04-20-2012, 01:10 PM
Hey Jimi! Glad to be around again. It looks like youre recreating part of exodus? Looks ambitious. :)

04-20-2012, 01:17 PM
yeah, yu know me, stone cold crazee!! But again, when I see you here on the forum, I just can't help but think of all those days when I couldn't rig my first model, (remember the bullfrog?) Wow! Long time ago now. Hey, I"m a grandfather for heaven's sake!:D Anyway, I'm almost done with the first installment of this project, and it is about the exodus. Which brings me to my next post.
And thanks everyone for the help, its much appreciated. I have plenty to think about as I try and pull this thing together. As always, the Wavers rock, and I'm so glad to be one.

04-20-2012, 01:25 PM
I don't know where yakima is. Is that good or bad? Is it in Washington state by any chance? Just wondering.

04-20-2012, 01:29 PM
Jimi: How time flies and yes its in Washington. :)

04-21-2012, 06:22 PM
I don't know where yakima is. Is that good or bad? Is it in Washington state by any chance? Just wondering.
It's in Washington, yes, on the desert side. I used to live nearby and from my point of view, YMMV, it's bad. But then, it's a desert.

Rendering wise, it looks great. :hey: