This blog is about games, right? So let’s play a small text adventure:

You feel a bit tired so you need a small encouragement which lets you have a look into your mirror. What do you see?

[1] A good looking effect artist! (continue reading at – 4 –)
[2] A creative & very smart person starring back! (continue reading at – 3 –)

– 3 –
You feel like you want to be an effect artist! That’s why you go into the basement and boot up your personality changer. (continue reading at – 4 –)

– 4 –
You’re an effect artist. What a coincidence!! Because this article could be interesting for you.

End.

@TychoCelchuuu asked me how this beautiful effect was done. Let’s lean back, relax and look at it for a while:

Source: Company of Heroes World Builder

If you already know what a simple particle system does, continue reading at – 5 –
A particle is more or less a polygon which is (most times) always aligned to the camera:
But particles don’t like to be alone so mostly you let your particle system emit a lot of them. With that you try to hide the fact, that you’re starring at a bunch of polygons. In combination they look more complex than they really are (especially when they move).
Of course you can then change some attributes of every particle over time like scaling, rotation, transparency and a lot more:
With such a particle system you can do really nice smoke and such stuff but for advanced effects you need more. And that’s why…

…I’m really stunned by the technology of the Company of Heroes engine! Because you need a lot more than a simple particle system to accomplish this effect:

1. The fire sparkles are not oriented randomly but into their moving direction!
2. The fire sparkles are stretched depending on their speed!
3. The fire sparkles burn where they hit the ground and create a new smoke effect. This means there’s a collision detection – and we don’t talk about GPU calculated PhysX here!
4. Last but not least: The core of this effect is a fire stream which isn’t built out of a massive amount of particles. This is awesome, because the stream never interrupts even when the tank would rotate very fast! But how is the stream done?

	Here you can see the stream and how it deforms when the stream source is moved. Looks really neat to me!No single particles are visible. Guess what the whole thing is made of?
	It’s a geometry. At first i thought a texture is moved along it but a close look reveals that the geometry itself is moved (especially visible at the end then the whole thing stops).I’m not 100% sure but i guess they colorize it via vertex colors so that the upper part gets first reddish and then fades out.

But how do they prevent the viewer from seeing the geometry from the side? Here you have the answer:
If you think that this remembers you on something, then you might already read my Homeworld Trails article.

The Relic effect engine is very powerful and if you want to know more you should have a look on this presentation.

If you want to see the flame thower in action you can use these videos:

I didn’t embed the video directly to avoid any tracking from Google and complications with the DSGVO.

I didn’t embed the video directly to avoid any tracking from Google and complications with the DSGVO.

Thanks at Ryan Pool for his help, ansers to my questions and his really cool CoH World Builder tutorials.

Update 1

NobleYad just mentioned this awesome thread about a spline-thicken-feature in Unreal. Wow! They use similar auto-aligned geometry-planes to generate pipes and trees! 8O