Comment by ghc
2 days ago
I've always wondered why voxel engines tend to produce output that looks so blocky. I didn't realize it was a performance issue.
Still, games like "C&C: Red Alert" used voxels, but with a normal mapping that resulted in a much less blocky appearance. Are normal maps also a performance bottleneck?
Hello, author here :)
I originally chose to go with axis-aligned blocks and hard axis-aligned normals because I liked the aesthetic. I've since slightly course-corrected; each voxel has bent normals which follow the surface. How much the normals are bent is artist configurable. This has the effect of smoothing out the look of the surface when viewing from a distance, but still gives the distinct blocky look when up close.
In terms of performance, there is a cost to having fully 3D normals per voxel, but it's certainly manageable. There's a lot of other, more expensive, stuff going on.
Before Minecraft, basically all voxel engines used some form of non-axis-aligned normals to hide the sharp blocks. Those engines did this either through explicit normal mapping, or at the very least, by deriving intermediate angles from the Marching Cubes algorithm. Nowadays, the blocky look has become stylish, and I don't think it really even occurs to people that they could try to make the voxels smooth.
Voxels have been around since the 1980s. The smoothness came from that beautiful CRT and its inability to display crisp images. Normals weren’t really used until early 90s and used heavily by games like Comanche by NovaLogic.
The reason why Minecraft voxels are blocks is because Notch (Markus Persson) famously said he was “Not good at art”. He didn’t implement the triangulation and kept them unit blocks. Games that had voxels AND were triangulated that came before Minecraft were Red Faction, Delta Force, Outcast just to name a few.
The point is, voxels aren’t anything special, no more than a texel, or a vertex, or a splat, a normal, or a uv. It’s just a representation of 3D space (occupied/not occupied) and can just as easily be used for culling as it can for rendering. The Minecraft style because popular because it reminds people of pixels, it reminded people of legos, and Minecraft was so popular
It depends on how the voxels relate to the gameplay.
Regardless of the original intent, in Minecraft the voxel grid itself is a very important aspect of the core gameplay loop. Smoothing the voxel visual representation disguises the boundaries between individual logical voxels and makes certain gameplay elements more difficult or frustrating for the player. When the visuals closely (or exactly) match the underlying voxel grid, it's easy for the player to see which specific voxel is holding back some lava or if they're standing on the voxel they're about to break.
In Minecraft you can, for example, clearly count how many voxels wide something is from a distance, because the voxels are visually obvious.
In Red Faction, you're never concerned with placing or breaking very specific voxels in very specific locations, so it's not an issue.
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> it reminded people of legos,
I don't think this should be understated. LEGO are easy and fun to build with and don't require a lot of artistic talent. The same goes for block-based games like Minecraft.
I think marching cubes is still decently popular in games with modifiable terrain, we just stopped referring to it as voxels