I’ve seen this effect in many games used for clouds or small dust cloud on ground to fire. Basically there’s a different static or animated texture for each n angle range from left to right and top to bottom. Depending on the camera view the texture on the billboard fades from one to another and everything fades out when camera gets too close so the billboard polygon won’t clip.
Are these kind of “multview” billboards supported in Unity or will it need to be written from scratch?
Maybe the reason I can’t find info on them is because the indsutry accepted term is not “multiview billboard” but something else.
PS. I am not asking about raymarching or volumetric billboards, those seem harder to implement and I’d assume much heavier on performance, at least for a flight sim and a sky full of “volumetric” clouds.
Thanks, i checked the pages and it seems a cool effect but advertised for solid geometry not seen from up close. Any ideas if these could be used for clouds, dust and fire?
EDIT: This won’t work for clouds, dust and fire because only binary transparency is supported and different views do not fade into each other but pop.
Still, thanks for trying to find a solution.
Sprite Impostor is a common term for these, but that’s a catch-all term that encompasses a ton of different implementations, some of which blend, some of which don’t. The specific implementation of the octahedral impostors technique that the Amplify Impostors is using is indeed aimed at opaque objects, but the general concept is easily applied to transparent objects. What I think you’re talking about would have be more referred to as “sprite turntable flipbook”, but that isn’t a term really used anymore and is thoroughly unsearchable. Today you might find more references to “doom style” sprites, as early 2.5D shooters often had sprites that showed different sprites depending on the angle, but those were also generally not blended between since the hardware of the time wouldn’t have been fast enough to do that. However there are examples of shaders for Unity that wouldn’t be too hard to modify to make them blend between animation frames.
The fading out when you get close however … that’s just basic view distance fading that’s pretty common for particle systems in general. Not something specific to the technique you’re looking for. I also don’t think I’ve seen a non-retro style game actually use a turntable flipbook in a game in … I don’t know, 15 years?
Also here’s a free implementation of octahedral impostors that might be easier to modify if Amplify’s doesn’t do what you want.
https://github.com/xraxra/IMP
Hi Bgolus and thanks for the ideas. It feels like I’m better off just writing this from scratch than creating a code bloat since I don’t need most features these projects provide.
I can only speak about multiview (not just horizontally multiview) billboards of clouds, smoke and flames, not sure if “turntable flipbook” fits the definition, and can say those are used in many AAA games to make things up close not look like a flat card with an animated texture with an alpha channel facing your camera or a X or star shaped interesecting quads. Specifically Skyrim does this for clouds and Breath of the Wild does this for flames and dust clouds. I’d imagine they would make some vfx look better as well like magical attack vfx. With these effects you’d probably want to render different views in your 3d modelling program, not in Unity.
As for solid objects, I haven’t payed much attention and I think for most objects just different poly count mesh LODs will work just fine, but for objects with complicated silhouettes unlike rocks, mountains and buildings such as medium distance trees, statues, more complicated architectural models an octahedral impostor would look better than a lower-poly version of the mesh during the transition to the highest LOD level. But this is not the effect I’m looking for, I’m specifically interested in clouds, dust clouds and flames since too many games stick to few quads, billboard particles or sprites that give away immersion from close distance and free camera controls.
As far as I know that’s not how BotW or Skyrim does those effects. 
Sometimes flipbook animation, and certainly scene depth and camera fading, yes. But the rest is subtle tricks done by rotating and stretching the geometry in creative ways.
BotW for example, fire particles have an “up” direction and a “movement” direction, and it aligns the up vector to the cross product of the camera forward and particle up, and then skews the top vertices of the particle opposite of the “movement” direction. Some variants just completely ignore the “up” vector and align themselves to the movement vector regardless of anything else, just like stretched billboards in Unity’s particle system. There are other tricks like changing the width of the particle depending on the angle to give it a sense of volume. I think they also fade out the particles if the resulting particle is being seen to close to edge on.
Really, BotW doesn’t even use any animated textures at all for their fire and smoke. It’s all fun shader tricks. Something like this:
Skyrim is much more simple. They very rarely used animated textures for anything and instead opt for a lot of very simple & cheap particles with the same texture. Maybe they might use some panning textures on mesh geometry. But otherwise they’re incredibly straightforward effects from a tech perspective.
If you can show me examples of them doing otherwise, I’d love to see them, but I played a lot of both of those games spending time picking apart their effects and never saw anything like what you mentioned.
Again, that’s not to say it’s not something people do, but usually there’s cheaper, easier techniques that get you 95% of the way for far less art cost (both artist time and runtime memory).
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Really appreciate the detailed discussion. I will post a proper response soon after I check the actual assets for these games with some unofficial modding and converter tools and prepare some closeup videos.
Thanks.
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Skyrim is pretty straightforward. People have dumped the entire texture library from that game and posted it online in the past (before being rightfully asked to take it down). BotW … Cemu & Nsight is a pretty awesome combination … so I’ve been told … … cough
A friend of a friend told be about this thing called “xentax”, not that I know anything about it.
Anyway, I’ll make an update post with some images and videos.
