follow path with trail

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22 posts
Joined: April 2013
Hi all,

I'm a very new Houdini convert (first time using it today) from many years of using other 3D applications and have already managed to build and destroy objects, create clouds, turn objects to liquid with a big smile on my face, Houdini sure is impressive.

Now I'm having a go at simple animation and I came across something I didn't fully understand and hoping someone could explain in a step by step way how to animate an object along a path with a trail OP.

I have made a cube and a nurbs path both in the scene view then I simply select my cube and then follow path and then the curve, hit enter and voila I have an object on a path.

Being curious about every button and option I found “trail” OP and thought I could simply apply the trail OP to the cube but I couldn't create one in the scene view, only in the geometry level so I double click the box object in the scene view to get to the geometry level and add a trail to the cube moving around the path but this didn't work so my first stop was the help file where an anonymous user posted this.

" The Trail SOP can of course only detect movement animated at the geometry level. It will not take account of transformations at the scene level. So you need either to animate at the geometry level, or animate at the scene level, for example to follow a path curve, and then use object merge, with ‘transform into this object’ set, to bring the animation into a separate object where the trails are calculated. "

Which I am unsure of so here am asking for assistance from more experienced users and seeing if its true about how friendly Houdini users are while I'm here




While I'm here my current system I am working on is windows 7 64 bit with a Nvidia gtx 670 (with latest drivers) running 3x monitors and the latest build of Houdini 12.5.376.

The viewport using open GL 3.2 does not show shadows at all when I select high quality lighting and shadows with a spot light and simple geometry in the scene, is this normal or I am missing something, using the wrong drivers etc as the tutorials I have watched clearly show shadows working in the viewport.

Sorry for the long read for my first post.
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3710 posts
Joined: July 2007
what help is suggesting is creating empty geometry object and use Object Merge SOP to get box's geometry (in world space), then apply Trail SOP

follow_path_trail.hip (77.3 KB)

Tomas Slancik
FX Supervisor
Method Studios, NY
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22 posts
Joined: April 2013

Thank you very much for taking the time to help, looking at your scene file made everything so clear in seconds, exactly what I have been attempting to do without success

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