Papervision3D Grass/Fur Effect

To me, “Shadow of the Colossus” represents the pinnacle of PlayStation 2 games. Aside from the fact that it’s one of the most artistic games I’ve ever played, it’s also one of the most technically brilliant games on the platform, pushing the PS2 to its limits with real-time motion blur, HDR rendering, a LOD landscape system, IK & physics system, self-shadowing and, of course, the impressive fur shading. However, the PS2 can’t handle all of those things done “properly”, so some were achieved with ingenious tricks and shortcuts, all covered in this inspiring article on The Making of “Shadow of the Colossus”.

Since reading that article I’ve always wanted to recreate the fur effect, and have now done so using Papervision3D. As I was hoping to use it on a recent project, instead of fur I decided to simulate grass:

The effect is achieved by drawing cross-sections of the fur/grass on a set of parallel layers – in this case I have 7 layers which, using 512×512 alpha-transparent textures with 4×4 segments, is pushing the limits of Flash/PV3D. However, because we’re only ever dealing with 7 textures, it can handle potentially infinite blades of grass – the example above has 3000. The grass is generated in real-time – I build the layers up by starting each blade of grass with a certain size & direction, and growing it out on subsequent layers. The effect looks fine when the camera is close to perpendicular or the normal of the planes, but things start to fall apart when the planes and camera approach parallel.

The grass highlights are created with simple gradients, and I’ve also rendered basic shadows to the dirt layer (although they’re barely noticeable with such dense grass). Each blade of grass has a random colour, weighted heavily towards green but straying towards blue/brown in rare cases. Creating the effect of the grass moving in the wind is a simple matter of moving each plane along the X & Z axis, with the motion increasing based on the distance from the base layer.

Being a huge fan of both Ico and SOTC, I’m really looking forward to seeing the next game from Fumito Ueda and Team ICO, and what they can do with the PS3 hardware.

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