Question about the use of Self.PointPostion in ICE

[Anonymous]

Today I have one question that need your help.
I have one Null and one Grid and connect as in the picture.
But when the subtraction result connect to Self.PointPosition, all grid points move to the position that its center is the center of Null object.
The result vector is the vector that connect from the old grid center to the grid point.
Can you explain me why the Self.PointPosition make the final vector like that?. I read many references in Autodesk use guide but cannot explain why the result(the Blue vector in the attachment of image file ).
It is very good if you can give me web links or detail help about that.
Many thanks and regards

Nguyen Duc Hoang

[grahamef]

Null.kine.global.pos is in global space, but self.PointPosition is in the local space of the object.

If you want the result in global space, you need to multiply self.PointPosition by self.kine.global using Multiply Vector by Matrix to put them in global space first before you do the substraction.

On the other hand if you want the result in self's local space, multiply null.kine.global.pos by the inverse of self.kine.global first.

[Anonymous]

Thanks for your help.

My point is that as in the attachment image file:

- when I connect the output result in Add node to Self.PointPosition in (Set Data) node, the output is very different with connect to Self.TMP in(Set Data) node. I want to know why?.

- I do this practice as guded in a video tutorials and I see no explaination for this problem.

Please see the two pictures below for detail:

1.Connect result to Self.TMP

 

2.Connect result to Self.PointPosition

Any help will be appreciated.

Thanks and regards

Nguyen Duc Hoang

[grahamef]

You are getting exactly what I would expect to get.

First, you subtract the local point positions (that is, the offsets from the grid object center) from the null's global position, and then use that value to set the local point positions. This has the effect of moving the points without moving the object center (effectively creating a simple deformation).

Next you display the new point positions (again, the offsets from the grid object center which is still at the origin) as vectors (which places the vector base at the actual point positions).

In this situation it might make more sense to display the point positions as vector trails, which puts the head of the vector at the point position (and therefore the tail of the vector at the object center).

[Anonymous]

Thanks for your email.

In the first I see that the position changed but I still do not know why the new position vector is CP2(as in the attachment file).Please see the attach file for details(see the red brush)

The second is understandable for me

[grahamef · Accepted solution]

When you set the new point position to the null position MINUS the old point position, you flipped the X and Z coordinates relative to the null (Y too, but that's uniformly 0 so it doesn't matter).

See the attachment:

[Anonymous · Accepted solution]

Many thanks for your help.

I see your picture and understand my problem.

My problem is that the misunderstand of CP2 vector. The right is in your RED vector.

Cheers

Nguyen Duc Hoang