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> *edit: btw I can tell you stories about volume rendering non-voxel data from CG production if you want. Yes!

dahart 10y ago
Long day, sorry it took a while... So, volume rendering in production. I was in the effects department at PDI/DreamWorks, and I used several different volume rendering techniques over the years. We all did, part of why it was such a cool place to work was how free we were to use or invent whatever techniques we wanted to get our shots done - most CG production is a lot more fixed pipeline and regimented than that. Particle rendering (aka splatting) is probably the main staple for volumetrics in the FX toolbox. Particles are best thought of as soft transparent spheres, but usually implemented as camera facing polygons. I used large volumetric particle sets for impact dust from feet & fight sequences in Shrek, and for smoke and fog and fire in later Shrek productions and in Madagascar. The visible texture actually comes from changes in particle density, and particle simulations were often in the millions of particles. We used a ray-marching volume renderer implemented inside of a shader for some of the foggy sets in the Shrek productions. Pretty much the same tricks going around ShaderToy today. Dragon fire was another ray-marching shader that would ray-trace spinning spheres, and then ray-march through a noise field inside each sphere. In one shot on Madagascar, I used a combination of particles and volume rendering and geometry when the boat blows it's horn and flattens the island. I happened to be working on the island's foliage as well. We didn't have low res standins for the plans for a shot this wide, and it was taking more than 12 hours to render IIRC. We wrote a script that culled any geometric or volumetric detail that projected down to smaller than a pixel, and it brought renders down to an hour or two, and turned out to cut something like 90% of the scene geometry. Doh.

Long day, sorry it took a while... So, volume rendering in production. I was in the effects department at PDI/DreamWorks, and I used several different volume rendering techniques over the years. We all did, part of why it was such a cool place to work was how free we were to use or invent whatever techniques we wanted to get our shots done - most CG production is a lot more fixed pipeline and regimented than that. Particle rendering (aka splatting) is probably the main staple for volumetrics in the FX toolbox. Particles are best thought of as soft transparent spheres, but usually implemented as camera facing polygons. I used large volumetric particle sets for impact dust from feet & fight sequences in Shrek, and for smoke and fog and fire in later Shrek productions and in Madagascar. The visible texture actually comes from changes in particle density, and particle simulations were often in the millions of particles. We used a ray-marching volume renderer implemented inside of a shader for some of the foggy sets in the Shrek productions. Pretty much the same tricks going around ShaderToy today. Dragon fire was another ray-marching shader that would ray-trace spinning spheres, and then ray-march through a noise field inside each sphere. In one shot on Madagascar, I used a combination of particles and volume rendering and geometry when the boat blows it's horn and flattens the island. I happened to be working on the island's foliage as well. We didn't have low res standins for the plans for a shot this wide, and it was taking more than 12 hours to render IIRC. We wrote a script that culled any geometric or volumetric detail that projected down to smaller than a pixel, and it brought renders down to an hour or two, and turned out to cut something like 90% of the scene geometry. Doh.