Sixth and Eighth: The Graphics of Halo 3

April 21, 2016

4-Environmental Flair

Water

If there’s one thing that gets brought up with Halo 3’s graphics besides lighting, it’s water. Water in Halo 3’s gameplay spaces is a very full-featured system which is used with impressively consistent quality throughout the game.

WavePicThe “next gen” water of nine years ago

Geometry

Halo 3’s water is animated geometrically, not just with textures and shading. The water is basically a surface broken up into lots of small polygons, where the height of the vertices is defined by a “wave” texture that gets updated frame by frame.

tess
Very roughly the sort of thing that Halo 3 does

In addition to the ordinary flow of water, dynamic splashes are added into the wave texture when objects and explosions interact with the water. This is useful in making it feel like water and other things exist in the same space as each other. As these splashes are much sharper than the normal waves, the polygon count of the mesh isn’t necessarily good enough for them to be smooth, and they can look somewhat “jaggy.” Halo 3’s overall low-poly appearance sort of helps keep this from looking too out-of-place or inconsistent.

The geometric surface is produced via dynamic tessellation on the Xbox 360, configured so that the complexity of the waves and the density of polygons is lower for more distant water. This avoids the high rendering cost of small distant polygons, and because there’s not a ton of sharp geometry fighting for each distant pixel, aliasing is reduced.

Physics

In addition to the water being affected by other things in the game world, it also applies basic physics to dynamic objects. Objects that have recently been acted upon will float on the surface until a timer expires, after which they slowly sink. If the water has a flow direction, floating objects are carried downstream.

Rendering

It’s common for transparent surfaces in games to have lighting that is simplified or inconsistent with the rest of the game world, but Halo 3 is relatively uncompromising. Water receives both the lightmap and dynamic lights, and generates complex reflections for each.

Interestingly, light sources tend to have large “rough specular”-esque reflections off the water surface, which are visible from underneath the water as well. It doesn’t look very physically accurate, but it gives the impression of light scattering in the hazy water. And perhaps in keeping with the art style, it keeps the scene decidedly non-dull.

Finally, water refracts objects below the surface. The effect is improved over in Halo 2, which had oddities like including objects above the water’s surface in the refracted image.


Foliage

Animation

Like the water, Bungie aimed to make the foliage lively. Some plants react to explosions and passing objects, just like the water. Tree branches blow in the wind, each tree often featuring multiple groups of branches animating independently.

The results are somewhat successful, the main weakness being that they’re less unified than the water. Bushes that respond to physics don’t blow in the wind, branches that blow in the wind don’t respond to physics.

 

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4 Responses to “Sixth and Eighth: The Graphics of Halo 3”

  1. Halo 3 is great. I wonder if modern games match the HDR. They don’t look like it usually… UE4’s lighting seems very high range. maybe its just the tonemapping.

    • Bungie’s Lighting and Material of Halo 3 presentation indicates that if the 360’s ROPs had better support for FP16, they would have used it and had massively higher dynamic range for the same memory footprint. Modern GPUs have good support for FP16 output (compute shaders have no trouble with direct FP16 access, and the ROPs have robust single-cycle FP16 capabilities), and the ideas behind PBR encourage mimicking realistic range… I’d be surprised if modern games don’t often beat Halo 3 by a large margin.

  2. Wow, this was really great! I learned a lot about from this. You did a great job explaining the different types of lighting, HDR, and the implementation of water and physics. Looking forward to more articles!

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