Houdini Roller Coaster help

[jetlag5]

Hi there,

 

Just wondering if anyone here has had any success at creating a roller coaster in Houdini, I'm trying to do this, with a loop, and continuously run into the issue of flipping normals or vectors, which affects my ability to A) build the rails along the backbone of the roller coaster, and animate a cart along the path, as it flips half way up the loop, and back down.  

 

I've essentially just done a curve to a resample to a polyframe, and it seems I'm missing a step before skinning and animating on that curve.  I've attached my hip file as well.  Thanks for your time!

Coaster_Test_v02.hip

[loopyllama]

You do not need the Polyframe SOP. You only need to set your path's up vector to 0 0 1. See the attached file...

rollercoaster_v01.hip

[jetlag5]

Thanks Loopy LLamma!  That helps.

 

I used a line with 2 points animated along the path (trail+add sops) to create the rails along the sides of the main backbone of the rollercoaster.  There is no flipping going on anymore.  The thing I do notice now, is that I lose the banking of the rails as the track bends and turns.  Is there a way to get this back using this method?  I've attached an image, and the hip file.  Thanks again for the help!

rollercoaster_v02.hip

[kgoossens]

This can help, although not perfectly stable it will give good results in most cases.

 

 

rollercoaster_v01-Orient.hip

Edited December 14, 2014 by kgoossens

[jetlag5]

Thanks kgoossens.

That solves a lot, if not all of my problems.  One quick question, how do you determine how far up to transform the curve after smoothing, and before the attribvop1?

[kgoossens]

Right now this is done just by manual tweaking, I'd need a bit more time to find a solution that would solve this automatically. 

[jetlag5]

Thanks kgoossens.  I've played around with it as well, and it seems each curve can be slightly different to transform.  I tried this with cursive text as a curve. (as in the track of the ride creates cursive text), and that doesn't work at all, at least not without manually moving the points around after the smooth, but that's not a procedural method by any means.

Edited December 14, 2014 by jetlag5

[kleer001]

Lol, it's not really helpful, but I remember that back in 1998 a fellow student was doing their Houdini work (in v1.0) by building a procedural roller coaster. So, it's totally possible.

[kgoossens]

Lol, it's not really helpful, but I remember that back in 1998 a fellow student was doing their Houdini work (in v1.0) by building a procedural roller coaster. So, it's totally possible.

With Loops?

[jetlag5]

Agreed Kgoosens, It seems the loops are the biggest issue in creating a fully procedural roller coaster.  I'm still trying to find a way to figure it out, for now, a hack would be to cut between shots, and use Kim's method for non loop shots, and Jim's method for looped shots.  That really isn't ideal, but when you're on a time crunch...

[kgoossens]

Hi Daniel,

 

I'm sorry that it might be too late for the project you need, but I was occupied with other things.

I've added a better solution, this one takes into account the velocity the car would have at a specific place to calculate the curvature. This means that you can do loops etc... The only "limitation" now is that you have to make sure that your car has enough speed before entering the loops, and you have to set the starting point on the curve. 

rollercoaster_v02-Orient.hip

Edited December 18, 2014 by kgoossens