How to get Point Normal Radiate from center

Forums Technical Discussion How to get Point Normal Radiate from center

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sl0throp: Member; 258 posts; Joined:; Offline

Feb. 24, 2011 8:49 p.m.

I have a poly circle that I am scattering points across. I am using a point sop to get normals but I can't figure out how to get the normals to point out from the center of the circle. These are non moving points to orient for copySop. I have attached a pic for reference. Thanks in advance for any help…

s

Attachments:
fromCenter_001.jpg (39.7 KB)


Soothsayer: Member; 874 posts; Joined: Oct. 2008; Offline

Feb. 24, 2011 9:02 p.m.

Try using -$TX,-$TY,-$TZ if they are world centered, otherwise offset appropriately. Normalize if necessary.

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circusmonkey: Member; 2624 posts; Joined: Aug. 2006; Offline

Feb. 25, 2011 4:07 a.m.

This scene file will help

Rob

Attachments:
rse_radial_normals.hip (47.0 KB)

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old_school: Staff; 2540 posts; Joined: July 2005; Offline

Feb. 25, 2011 1:44 p.m.

With a random point cloud, you can do a few things.

First is a trivial curent_point_position - centroid_of_point_cloud using either bounding box or centroid local variables in the Point SOP.

But what if you have a wildly fluctuating point cloud with interesting concave and convex shapes and you want your radiating normals to take this in to account? Use Volumes of course. Take your point cloud, build a fog volume from them, convert to sdf then use the Volume Analysis to build three gradient fields (which is the distance and direction to the sdf limit surface which is the surface normal btw) and then transfer in to the point cloud as Normals.

See the attached hip file for all three versions.

Attachments:
create_radiant_normals_from_point_cloud.hip (92.0 KB)

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sl0throp: Member; 258 posts; Joined:; Offline

Feb. 25, 2011 7:29 p.m.

Thanks Jeff…that is a very interesting file. Thanks to Rob as well who was also right on for what I needed.

s

Edited by - Feb. 25, 2011 19:44:30


Soothsayer: Member; 874 posts; Joined: Oct. 2008; Offline

Feb. 25, 2011 7:43 p.m.

Volume analysis sop! Ha! If I had known that some time ago!

Great Jeff, I'm always amazed by what you can do with just nodes. Where do you learn all that stuff!

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koen: Member; 793 posts; Joined: April 2020; Offline

Feb. 25, 2011 11:16 p.m.

here is one more way, might not work perfectly for this case, but I found it very useful for point clouds. It calculates the normal by taking the difference from between the position of a point and the average position of a local neighborhood.

it's pretty fast.

Cheers,
Koen

Attachments:
point_cloud_normals.hipnc (62.2 KB)
Screen shot 2011-02-25 at 8.13.58 PM.png (110.7 KB)


circusmonkey: Member; 2624 posts; Joined: Aug. 2006; Offline

Feb. 27, 2011 3:13 a.m.

I must admit when Jeff posts > I read…..

PS when are we getting more Old school Blog >

Rob

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old_school: Staff; 2540 posts; Joined: July 2005; Offline

Feb. 28, 2011 2:29 p.m.

Recording one today! Finally…

There's at least one school like the old school!

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