Point a vector along curve direction

Forums Technical Discussion Point a vector along curve direction

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Soothsayer: Member; 859 posts; Joined: Oct. 2008; Offline

Feb. 8, 2010 6:13 a.m.

How would I point the normal vector of curve-points in the curve direction?

(So that they flow along it rather than all show in one direction)

Like the left three vectors in the picture below:

Attachments:
vec.jpg (17.5 KB)

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Jobless


tamte: Member; 8554 posts; Joined: July 2007; Online

Feb. 8, 2010 6:46 a.m.

try polyframe SOP

entity : Points
style : Two Edges
tangent name : N
make frame orthogonal : off
other fields empty

Tomas Slancik
FX Supervisor
Method Studios, NY


mawi: Member; 242 posts; Joined: Jan. 2008; Offline

Feb. 8, 2010 3:08 p.m.

Or…

In point SOP / Force tab, add edge force.
This Will give you a edge_dir attribute pointing along the curve.


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

Feb. 8, 2010 3:11 p.m.

Poly Frame with the options above generate tangent vectors at the points.

Use the Point SOP to build vectors that point at the next point:

Point SOP > Force Folder > Add Edge Force

This adds two attributes. Look at edge_dir. It generates normalized vectors that orient to the next point.

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


graham: Member; 1906 posts; Joined: Nov. 2006; Offline

Feb. 8, 2010 3:17 p.m.

If you use the PolyFrame with Style set to First edge it should give you the same result as adding an Edge Force.

Graham Thompson, Technical Artist @ Rockstar Games


Soothsayer: Member; 859 posts; Joined: Oct. 2008; Offline

Feb. 8, 2010 7:02 p.m.

Thanks for the many tips.

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Jobless


maxedout: Member; 42 posts; Joined: Jan. 2010; Offline

Feb. 9, 2010 2:37 p.m.

hi guys .. thanks for all the tips … i have however tried the pointfunction in point sop:
point(“../”+opinput(“.”,0),$PT+1,“P”,0)-$TX … so on and so forth …..

i tried the other 2 methods too and have few doubts. With polyframe the direction of normals is reverse than as what i get using point function.. and somehow don't understand the edgeforce method.

have attached the file … maybe someone could check and explain pls.

thanks

Attachments:
Normals_directions.hip (79.5 KB)


Anonymous: Member; 678 posts; Joined: July 2005; Offline

Feb. 9, 2010 3:23 p.m.

added edge example

Attachments:
normals_directions_fix.hipnc (82.4 KB)


maxedout: Member; 42 posts; Joined: Jan. 2010; Offline

Feb. 9, 2010 6:56 p.m.

thanks swann… that works .. however i was hoping if you could reverse the normal direction on polyframe

thks


graham: Member; 1906 posts; Joined: Nov. 2006; Offline

Feb. 9, 2010 7:07 p.m.

Append a Reverse SOP before the PolyFrame and you'll get the result you want.

Graham Thompson, Technical Artist @ Rockstar Games


maxedout: Member; 42 posts; Joined: Jan. 2010; Offline

Feb. 9, 2010 7:17 p.m.

ohhh great.. thanks for your help graham.


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

Feb. 9, 2010 8:22 p.m.

As this is a very interesting thread I wondered if I could push it further. I wanted to create a tool that could aim a custom vector using the handle from the line sop to control the direction. I am unable to even via a vop sop control the direction of my custom vector. Can someone give some pointers on the handle aspect and where I am going wrong with my vector.

Rob

I have updated the file with another example this time I have been able rotate the vector. In the details view you can see the aim attributes values.

Edited by - Feb. 9, 2010 20:47:28

Attachments:
vectorAim.hip (130.4 KB)

Gone fishing


Soothsayer: Member; 859 posts; Joined: Oct. 2008; Offline

Feb. 9, 2010 8:26 p.m.

I have a related question:

How could I point the normal of a particle in its direction of travel?

Edit: Sorry, I figured it out the second I hit the post button…argh…velocity…

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Jobless


graham: Member; 1906 posts; Joined: Nov. 2006; Offline

Feb. 9, 2010 8:52 p.m.

Something like this?

I just use a Point SOP and promote the N control in my case and then create a Vector handle and bind the N parms on the asset to it.

Attachments:
vector_pointer.hipnc (50.4 KB)

Graham Thompson, Technical Artist @ Rockstar Games


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

Feb. 9, 2010 9:05 p.m.

Graham… Cheers

My contribution. A small tool that can aim a custom vector. I've found it very useful indeed

rob

Attachments:
rse_sop_vector_aimer_v001.otl (18.8 KB)

Gone fishing

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