# Noise 3D - position pass

**URL:** <https://forum.logik.tv/t/noise-3d-position-pass/8805>\
**Category:** Flame Questions\
**Tags:** expressions, noise, position\
**Created:** [July 19, 2023, 3:38pm UTC](https://forum.logik.tv/t/noise-3d-position-pass/8805 "2023-07-19T15:38:28Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![David.Marin](https://avatars.discourse-cdn.com/v4/letter/d/a698b9/32.png) [@David.Marin](https://forum.logik.tv/u/David.Marin)\
**Post date:** [July 19, 2023, 3:38pm UTC](https://forum.logik.tv/t/noise-3d-position-pass/8805/1 "2023-07-19T15:38:28Z")

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Hey all,

I’ve seen an interesting technique in Nuke, and I’m trying to apply it in Flame, haven’t quite succeeded yet.

This is coming from here, around min 4:15.

[![](https://us1.discourse-cdn.com/flex020/uploads/thedepartmentofexternalservices/original/2X/8/8b57046d3c5f8ae65261bac40706c6d74446a80a.jpeg "Compositing EPIC VFX Godrays | Nuke Tutorial") ](https://www.youtube.com/watch?v=PqbqxnBFOHg)

I want to add a 3d noise on the surface using a position pass. As I understand it, he is multiplying the noise by the color channels in the alpha. With the expression: noise(r,g,b)

Can we do it or something similar in Flame?  
Thanks

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**Author:** ![milanesa](https://avatars.discourse-cdn.com/v4/letter/m/b77776/32.png) [@milanesa](https://forum.logik.tv/u/milanesa)\
**Post date:** [July 19, 2023, 4:56pm UTC](https://forum.logik.tv/t/noise-3d-position-pass/8805/2 "2023-07-19T16:56:28Z")

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Not in Flame now, but I have the feeling I have seeing a Matchbox for it.

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**Author:** ![cnoellert](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.logik.tv/cnoellert/32/559_2.png) [@cnoellert](https://forum.logik.tv/u/cnoellert)\
**Post date:** [July 20, 2023, 5:42am UTC](https://forum.logik.tv/t/noise-3d-position-pass/8805/3 "2023-07-20T05:42:02Z")

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Create a frame of color noise and multiply your ppass but I suspect the noise function is adding noise, not multiplying it.

Maybe first multiply that colored noise frame by some value… example 2.0, and then subtract half that value from it, 1.0, and then add it to the ppass. That should give you negative values as well as positive ones.

Can’t remember for certain but I think LS\_vops will do simple vector math. Otherwise you can do it with color sources and the comp node.

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<div class="post-metadata">

**Author:** ![David.Marin](https://avatars.discourse-cdn.com/v4/letter/d/a698b9/32.png) [@David.Marin](https://forum.logik.tv/u/David.Marin)\
**Post date:** [July 20, 2023, 1:58pm UTC](https://forum.logik.tv/t/noise-3d-position-pass/8805/4 "2023-07-20T13:58:34Z")

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Thanks for that. There is matchbox called LS\_Vops, I guess this is the one that you mean. It is not working for me at the moment, but I will keep trying!