This is not only the first header picture i use for an article, it shows also one of my favorite effects of Homeworld: The trails. But the engine effects don’t only consist of trails.
Engine Glow
The engine glows i know, are crossed planes which maybe fade out if you look in a narrow angle at them. But Homeworld has two interesting approaches how to do engine glows.
Sorry for the color bending, it’s not that strong in the game! I hope you can see, that these are three slightly animated “spheres” sticked into each other. So they get a nice volume for their engine glows for the big ships. Here you can see the geometries:
Of course, the shader has to fade out the sphere polygons depending on their angle to avoid the hard edge you see in the picture above.
The effect for smaller ships is a bit simpler. They seem to use several round sprites and scaling them down to create kind of a “tail” (move up and down if you can’t see it, maybe you’re in a bad spot of your flat screen):
In this Wiki you can read about a “iSparksPerPath” parameter which is described as “This graphic seems to be accomplished entirely out of one round effect repeated in the below fashon.”
It was really interesting to see this, because i saw this idea (to use several sprites for an volumetric effect) for example in StarForge:
Source: StarForge First Playable Release
At the “peak” of the spotlight effect you can clearly see the circles. The color bending in the wider base of the spotlight effect comes from the GIF – it looks fine in the original video! Anyway, i think it’s an interesting approach and besides of the “peak” it looks good to me.
Engine Trails
Homeworld “hides” this by covering their peak with the trail. I would have thought, that the trail is a dynamically generated crossed plane to make sure you see it from any angle. But i was wrong:
Here you can clearly see that it’s only one plane and it looks perfect if you don’t do what i did here. That’s a really good solution in my eyes because you avoid to double the polycount. Of course, it depends of how expensive it is to align the trail to the camera of the player.
And trails aren’t the only thing they handle like that. Bullets and muzzle flashes are also “just” planes:
But there are some things i don’t understand. Here you can see the engine setup of the “Interceptor” ship:
As far as i understand, the long thin lines are the limits for the engine glows (the round sprites). Ok that’s clear but i don’t get the function of the white engine meshes. First i thought they define the shape of the trails, but it’s not like that. The trails are just a plane and you can define the width of them in a script file. And even if the 2 outer shapes have a function, what’s up with the one in the middle? I can’t see anything in the game:
If you can read this, you’re really interested in space games or Homeworld or engine effects. Cool! Feel free to write a comment if you know something about the setup or have a suggestion.