Anchor points problems

Hello guys, i'm trying to use Grasshopper with Kangaroo for emulate only-compressed surface for the construction of a masonry vault system.

My problem is when i close the program and i'll open this in another moment: the correct surface that i've generated at the first time not corresponds at the same that grasshopper generate after.

Here the pics.

Sorry for my rusty english :D

Replies to This Discussion

Permalink Reply by Daniel Piker on July 14, 2011 at 3:51am

Hi Maurizio,

It looks like you are moving the anchor points during simulation to alter the surface.

When you do this, if you Reset the simulation, or save and re-open the file, the anchor points may not correspond to the same parts of the mesh.

This is because Kangaroo works as follows :

When Reset=True, Kangaroo compares the positions of all the inputs and decides what is attached to what.

For example, if an anchor point starts in the same position as the end of a spring, that spring end will be anchored during the simulation. So when the anchor point is moved in Rhino, the spring will move with it.

However, the geometry produced during the simulation is only stored temporarily, and unless you bake it, it will not be the same when you Reset or re-open the file.

When you switch Reset back to True, the temporarily deformed mesh returns to its starting/input geometry, but the Anchor stays in its moved position (because Grasshopper cannot move actual Rhino geometry - it only draws on top of the viewport). So when Kangaroo checks what connects to what, it sees that the anchor point no longer coincides with the end of that spring, and when you run it again they are no longer attached.

I hope this makes things clearer

Permalink Reply by Maurizio Barberio on July 14, 2011 at 4:36am

Thank you Daniel for the answer! Then there is no solution for my problem, i'm forced to bake the mesh and work whit this for the succesive model, that's right?

My dream is the connection, in the script, between the physic membrane and the following steps of the model: division, panelling, etc...

However congratulation for the plug in, it's impressive!

Permalink Reply by Daniel Piker on July 14, 2011 at 5:49am

Actually there are ways you can avoid having to bake the mesh to use the deformed version downstream in your definition and still save the file.

One option would be to make lines from the starting positions of the anchors (on the edges of the original mesh) going to the positions where you want them to end up.

You can then use a PointOnCurve component to slide points along those lines.

So next time you open the file, you set the slider to 0, and Reset=True, then switch to Reset=False and slide it to 1 so the anchors move to their target positions.

Permalink Reply by Maurizio Barberio on July 14, 2011 at 5:50pm

Oh Daniel, it's perfect now! Thank so much!! :)

Others questions: What's the units of measure for the stiffness? How do i calibrate this parameter for a stone construction? Are there some list of values for this?

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