Group from points that are inside of another geometry

[gekkonier]

Hi folks!

 

First of, I'm a noob, so maybe this task seems to be very basic.

 

Lets say I have a grid. Then I have a polysphere. Both of them are inside an geometry node.

I would like to delete all points from the grid, that are not covered by the sphere.

 

Would be the correct way to somehow paint a color onto the grid with the sphere and use that to delete with an expression?

 

I don't know how this could work, and I'm not sure how to feed Dr. Google with this - I think basic - question.

I'd like to copy boxes onto the grid, but only where it intersects with the sphere. The copy node has a group parameter so I thought this would be the way to go.

I'd like to animate this effect.

 

Thank you for reading

Edited October 20, 2015 by gekkonier

[davpe]

hi, this is very simple. 

 

inside your object:

1) create Group SOP

2) attach your grid to the left input and set the entity to points

3) inside the group SOP, make it a "Bounding" mode and set type to Bounding object

4) attach your reference geometry (sphere in your case) to the second input of the group SOP

 

all points on the grid with a location inside the sphere become members of newly created group.

 

5) you can delete points that are not part of the group by putting down delete SOP, setting it to points mode and selecting the group you created.

 

btw. you can skip creating the group if you want to delete points inside sphere. delete SOP alone allows you to delete based on bounding primitive too but it's limited to box or sphere primitive (which may be ok in your case since you are using sphere anyway). but if you wanted another shape you have to use the group SOP which allows you to use any object.

 

to copy boxes on points in group

1) create a copy SOP

2) connect your modified grid to the right input that says "Template to copy to"

3) connect your box to the other one that says "Primitives to copy"

 

now you should see the box copied onto template points.

 

you can animate template points by simply animating the bounding object used to group/delete points.

[davpe]

...and yes, you can also color the grid points based on proximity to the sphere and then delete points by color. that would be more steps to do though and generally less efficient performance wise. anyway, you would have to: 1) convert the sphere to volume 2) scatter points inside the volume 3) make these points red (for instance) 4) make grid points black 5) use attribute transfer to copy red color from sphere to the grid 5) use delete SOP to delete by expression 6) the expression would look like this: $CR<1 (that means select all the points that have color with red channel value lower than 1). the box instancing part stays the same.

 

if you are wondering why you had to convert the sphere to volume and scatter points in it first, the reason is that attribute transfer SOP use points (or other geometric elements that you can specify) to transfer an attribute. so you have to fill the sphere with something in order to sample its volume rather than just surface.  

[gekkonier]

Thank you very much for your explanations!

I really appreciate it!

 

I made this for you:

 

https://youtu.be/OgZ7kGKKQTw

 

 

Here I used the group node with bounding geo method, really easy to use!

Then I wrote a obj sequence and diddled a bit in fusion.

 

I will study all the sop nodes, there are really cool ones!

Edited October 20, 2015 by gekkonier

[davpe]

:DD awesome! keep it up man ;-)

[gekkonier]

I found this tutorial too, very cool: