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Help - Keep points on Y facing geometry?

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Hey guys,

I'm just getting into Houdini (have been working in comp for the past 6 years) and I need help with a most likely simple question.

I have some geo in my scene that I scattered a lot of points onto. I'd like to only keep the points on the Y axis.  Like imagine a camera above the character looking straight down. All the geo it sees should have points scattered on it and nowhere else. Do that make sense?

Any help on this would be great! I am hoping to take these points into a particle sim and use them to drive a smoke sim.



Edited by Nightingale
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24 minutes ago, Noobini said:

something like this ? I've set up 2 scenarios, one is Y facing (up) and the other is camera facing...


Thanks for the response!

Unfortunately the file you provided gives me a lot of errors.

Ideally, I want to scatter points all over the geo. Then blast keep only the points that are looking up. I also wanted a ramp that I could control the Y falloff so I can keep some points that are not 100% looking up but close enough.




Edited by Nightingale
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I don't have H15 installed but here's the gist of it....I think you can replicate in 15...(you can see from the pic there's tolerance of 10 degs for the Y facing points...after that you can blast the group however you like)


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Okay I see what you're doing now. You use a group and use the normals section to create a group of points.

When I do it, It'll create a group of 0 points when the "Spread angle" is less than 90 or it has all the points for a spread of over 90.




Edited by Nightingale
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see my Init_N there ?....that's to initialize the Normals...now I'm not an expert myself so I can't say to you if it's critical or not...I just put it in to be safe...

so in your case, below the pighead geo, initialize your Normals (points) with an Attrib Wrangle, put in it:

@N = @N;

see how that goes...

(oh wait, let me chuck in a scatter and see how I go...)

Ok, now that I've chucked in a scatter...the Init_N is crucial...before, I didn't have a scatter, my setup would still work......but with a scatter, the N must be properly initialized, otherwise it won't work.

Edited by Noobini
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