View Full Version : force Lightwave to evaluate item's position?

11-05-2010, 02:37 PM

Is there a way to force lightwave to evaluate (expose?) an item's position at every frame?

I've got an animation where I have an object following terrain (on the y axis) via nodes. It works great if I keyframe the x and y positions for the object at the start and end of animation.

What doesn't work, though, is if I try to parent an object to the animated object and displace the parented object in the same way (y axis via nodes). The parented object only has a keyframe at 0.

I think what is "broken" is that Lighwave isn't evaluating (or exposing?) the position of the parented object to nodes at each frame, so the nodes aren't affecting the object after the first frame.

Does that make sense?

please help! this seems like a huge bug.

11-05-2010, 03:48 PM
this probably isn't exactly what you're looking for but may help as a workaround

Apply soft FX to your item but set the operator map to "none" then hit calculate (this shouldn't take too long).
Then under the edit fx tab use the edit tool to select a point on the mesh (I guess one that's near to the pivot of the item) then under the "commands" drop down select makepath. This creates a null with a keyframed motion path following the point you selected.

11-07-2010, 02:49 PM
What doesn't work, though, is if I try to parent an object to the animated object and displace the parented object in the same way (y axis via nodes). The parented object only has a keyframe at 0.
Works here. Can't think of a reason why it doesn't work for you. Maybe you can post scenefiles.

11-07-2010, 06:19 PM
I guess it really depends how that displacement is actually calculated.

In this case simply parenting the null (green disc) to the object (orange ball) does not work as the displacement is done with some DPont magic rather than using a map. I'm with monovich on this one & would also love to know how to get that bugger of a null to follow the nice ball around :)

Any takers ?

11-07-2010, 07:43 PM
It's a displacement node. It moves the vertices of the ball mesh. Displacement does not move the item position. If you look at the axes of the ball, you see that null is tracking the ball's item position exactly as it should.

The bug is people confusing vertex displacement with item movement.


11-07-2010, 07:48 PM
I need some clarifications, because the premise is not stated clearly enough for anyone to confirm or debunk. But I can say why ADKs setup fails, because he provided a scene.

ADK. In your example the green disc can't follow the ball in y because the balls y movement is merely mesh displacement, not item motion. Parenting item A to item B, will make item A follow item Bs pivot/locator, not it's mesh. The mesh can go wherever.

Monovich. How are YOU making the "object following terrain (on the y axis) via nodes"? Are you using the native Node Displacement Editor or DPonts Node Item Motion motion modifier? And, how complex IS your setup really (what are the dependencies; how many evaluation passes would it really need). Preferably upload something or else the setup and problem is anyones guess. Unless ofcourse it's the same as ADKs.

EDIT: meee... I got bested by one of the best. :)

11-07-2010, 08:10 PM
:thumbsup: thanks for the explanations Jarno & evenflcw, makes perfect sense & I should have figured that one out.

That's why all my nodal noodling should come with a disclaimer ...
"danger ... nodal noob at the wheel ... steer well clear"

But where's the fun in that.

11-08-2010, 08:02 AM
hi guys. thanks for the responses. I'm out of town until tomorrow but I'll upload when I'm back.

For the terrain, I'm displacing it with nodes.
What I'm doing is creating a texture displacement for the terrain with a 2d procedural texture (world coordinates checked). I'm splitting the vector, pulling the y channel, and plugging it into the displacement for the object - but not before storing it with the Pom's store node.

Then, for the object following the terrain, I'm using Node Item Motion. I grab the same texture with the Pom's node and pipe it into the y position of the object.
For both of the above I'm using the output from the color channel. For some reason this has worked best for me.

Doing this, the object follows the displaced terrain perfectly. I can keyframe X,Z and it follows on the Y.

I was going to try to make a car rig (this is all about learning), so I created another null, parented it to the null that was following the terrain correctly, but tried to override the y position with the SAME node item motion setup that I used for the master null. Theoretically it would be getting the proper parenting on the X,Z, and then following the terrain nicely on the Y. This would be a nice way to set nulls for the base of each wheel. Its fast and interactive.

The problem is that when the object is parented using normal parenting, dponts parent node, or if its position (x,y,z) is modified in any way with nodes then it quits following the terrain on the Y. I've tried a half dozen node setups in an effort to get around this somehow, but everything I've tried has failed: I just can't get the null to follow the terrain (using nodes) at all when parented to another object.

I know there are other ways to do this (vehicle rigger does it with a different method for the wheel nulls) but I'm trying to learn nodes and this has been a good learning exercise for me. Unfortunately I spent the better part of a day trying to figure this out before concluding that it might be a lightwave problem (not evaluating or exposing the item's position), not my bad nodes.

Does this make sense?
Its being done successfully here, so maybe I'm just doing something wrong: