# How to make light beam with volume scatter correctly?

Hi guys, I have trying to make some light beam emmit from a car headlight.
However, the light always been scattered too much and cannot achieve the look I need.
I tried to constraint the light path with a cube, by making a long cube, I can finally make it work like this.

but the problem is, the light source has to be in a very long cube, which is not possible for car headlight since it’s too short. So I was wondering if there were any workaround to make the same look in cycle?
Or maybe some other tricks?

Cycles is not optimized for this kind of situation, so the result will be a bit noisier than normal…
But the workaround would be to change the light strength based on the incoming vector.
For example, if you use Dot(Incoming, Normal), you’ll get the cosine of the angle between those vectors, so if that value = 1 it means the incoming vector is parallel to the normal vector. In the same way, a value of 0.5 will correspond to an angle of 60º…

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think i am gonna review some math knowledge for now.
Thanks for helping. learnt a lot from your post.

Thanks, i think it’s pretty good solution if no environment light. But i think i may need to put in a poor lit environment rather than no light. Which will be different. Thanks anyway. Now i know how to do it without env light.

A few years ago the raceing sim GTR2 had faked headlight beams as textures.IIRC 4 sides,4 textures each headlight,positioned like a cross (top and side view), like double sides planes, if that makes sence.

they looked similar to this.

the beam into a emission shader with transparent backround.

So this Texture should be plugged into color node of a emission shader?
I have not used this before, but it seems to be used more like in post-production? I mean in ps, using this texture as a layer to fake the beam?

yes its fake, but its works if that is all what is needed.you can add glare node in compositing as well if you want.

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Sorry but i am still a little confused,
The map is the shape of the light beam, if i plugged into mix factor, the white area(the beam shape) will be the emitting source, like how we create a leave using texture map.
Is there anything i am mistakenly understood?

This is an awesome technique. Thank you for posting.

I don’t deserve your kind thanks. Thank cgmatter for that awesome tutorial.

Haha, seems you can show some romantic to your gf now~
Good luck

LOL - That photo is 20 years ago

EDIT: She’s still gorgeous. Me, hmmmm

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Lol. Stay safe~
Best for you and your wife~

You too. The downside is, we are both in lockdown, in different countries. I was due to move by the end of May, but now, not so likely

Wow, that’s sad. hope you can find way to get reunion!
Stay safe anyway~

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here a quick setup,hope it helps

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wow ,this is a clever way.
The result looks so good!
Thanks for showing me, i learnt a new skill!
Gob bless you!

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that is looing nice and better then just an emission mesh!

where can we get the light beam image to reproduce this effect?

thanks
happy bl

He has mentioned this site.