Interactive constraint on surface

[eikonoklastes]

Hi, please see the attached Cinema 4D video of what I am trying to replicate in Houdini.

I want to interactively position an object on a surface using handles.

I made some progress with the Creep SOP, but it has several limitations:

• it deforms the source object, which I don't want
• it doesn't have viewport handles, so I have to edit the node parameters, which is undesirable (I have a lot of objects to manually position, so I want to make it as easy as possible)
• it doesn't work with polygonal objects

I don't mind using VEX or an Attribute VOP to achieve this.

Thanks.

Slide_on_Surface.mp4

[tmdag]

What you need to do is:

1. check Normal of you object in point of interest

2. build rotation matrix and apply rotation onto your object

3. move your object to point of interest

There are many ways to do it:

To check Normal of your object in point of interest you can simply create create point on that object, or RAY a point or attribute transfer carve etc

To build rotation matrix and apply rotation you can use dehidral(set(0,0,1), v@N); v@P *= yourmatrix;or just use copy sop which will do it for you

Edited March 10, 2019 by tmdag

[eikonoklastes]

Hi Albert, thanks for the quick response. I'm sure your method works, but I am brand new to Houdini, so pretty much everything you said went flying over my head. However, I did find a much simpler solution, using the Sticky object.

I just need to project UVs onto the object, and everything works fine, especially with Wrap U and Wrap V turned on. I've attached a clip.

Cheers, and thanks again.

Houdini_Sticky_Object.mp4

[tmdag]

oh, nice! i dond't know such a thing exists  happy to learn something today as well!