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Tranimatronic
07-17-2009, 09:37 AM
Hi guys - I have been playing with Node Item Motion, and im not getting the results I expect. I was wondering if anyone has any suggestions ?

I have 2 nulls and a displaced ground object. Null 1 is above the ground, and null2's motion is controlled by Node Item Motion.

I use Null 1 Item info to give a worldspace vector and create a straight down direction and feed both of these into a RayCast. This returns me a distance of how high the null is above the ground. I subtract the distance to intersection from the Y scalar of null1 and plug the new X, Y and Z coordinates into the item motion.

To me the second null should follow null1 but to the contour of the ground object on the Y axis

it doesnt.
It either follows null1 exactly or follows it X and Z but Y=0. My understanding is if it didnt intersect with anything it should return -1.
Played with my direction vector, but nothing
I thought the item motion might be happening before displacement, so I froze the displaced mesh and tried it with that, but that didnt work either.

anyone any ideas ?

Tranimatronic
07-17-2009, 10:15 AM
just tried adding output into closest point node for the ground object and im getting a result closer to what I expected, but the result is so jerky as it snaps from one point to another that it isnt really any use.

Its all kind of difficult when you cant debug the result. Is there any way of outputting the raycast result to screen ?

I suppose I could try transforming null1's position vector by the direction*distance to intersection.

Any advice greatly appreciated :thumbsup:

Tranimatronic
07-17-2009, 11:46 AM
Its the RayCast node - always evaluating to zero.
Does anyone know whether it returns a distance to the surface or the point of intersection ?
Cheers

dpont
07-17-2009, 01:21 PM
We couldn't get LW raytrace functions or nodes
in displacement or motion handler,
More easy to use a Particle emitter with a Collision object,
then using FXLink or Particle Info node.

At least for fun, there's a Boolean node which works in Item Motion
node editor, it can detect if the NULL is inside or outside a given
target mesh, then it output the distance as a delta vector,
there's still a problem to 'freeze' the collision position.

75378

But here is what you get,

75377

Denis.

dandeentremont
07-17-2009, 01:50 PM
Unless you are trying to achieve this specifically with Node Item Motion, you can always try "Sticky"

ftp://ftp.newtek.com/multimedia/movies/w3dw/Sticky.mov

Tranimatronic
07-17-2009, 02:08 PM
Thanks !!
That explains it.
awesome tool BTW

Tranimatronic
07-17-2009, 05:53 PM
I tried Sticky and I wasnt too impressed. It seemed a little inaccurate, often the center point slipped under the surface, and slow - the align to surface was unusable, and kept flipping the object . This may be my fault - im not very familiar with using sticky.

I was hoping to create a vector from three intersections and keep the vehicle above the uneven ground (and orient it correctly)
Im now looking into other methods

Thanks for the suggestions !!

monovich
07-17-2009, 06:59 PM
vertigo also works nominally well