# circle normal

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how I can do that with vop ?

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hey,

there is a thread in the general questions sections named "learning vops", i'm not 100% shure if your specific question is discussed there but maybe you should take a look.

cheers

here you can find an example how to build a helix ore spiral with vops, maybe a good starting point for you problem http://forums.odforce.net/topic/12669-how-to-create-a-spiral-curve-in-sop/

Edited by hatrick
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In a attrib wrangle:

```@N = cross(@P, {0,1,0});
@N = normalize(@N);```

A cross product gives you a vector which is perpendicular to 2 other vectors.  Here we treat @P as one vector (ie, an arrow from (0,0,0) to each point), the y axis as another vector (0,1,0), the cross product gives you a vector that orbits around the y-axis.

This vector will get bigger the further away @P is from the origin, so you run a normalize() to make it of standard length.

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In a attrib wrangle:

```@N = cross(@P, {0,1,0});
@N = normalize(@N);```

A cross product gives you a vector which is perpendicular to 2 other vectors.  Here we treat @P as one vector (ie, an arrow from (0,0,0) to each point), the y axis as another vector (0,1,0), the cross product gives you a vector that orbits around the y-axis.

This vector will get bigger the further away @P is from the origin, so you run a normalize() to make it of standard length.

thankxxxxxxxxxxxxxxxxxxxxx

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in VOPS:
1. plug your grid into an AttributeVOP´s first input.  Dive inside.

2. from your globals, get P

3. connect it to a cross product node´s upper input (or lower to change rotation direction)

4. create a constant node of type vector, set values to 0,1,0 and plug into lower input of the cross product (or change input order if you wann rotate your normals the other way around, see above)

5. plug the output of your cross into a normalize

6. plus that into globals "N"

done.

keep in mind that this will of course change/screw your shading, since the normals are used for shading

hth

fuat

Edited by fuat

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