Content-Driven Multipass Rendering in UE4. Pretty things made with code.

Elyaradine

I didn't attend this talk at GDC (there was another one at the same time that I wanted to go to), but imo it's very good. The material he covers isn't trivial, but (maybe as with all complex things?) it's layers upon layers of easy things combined in interesting ways to produce stuff I hadn't thought of trying before.

But also, I just like seeing pretty things, whether it was made by someone painting with pixels, or someone painting with code. :D

It's obviously heavily focused on Unreal Engine, but as with almost all things to do with game engines, I'm quite sure you could do this with any other engine given some wrangling. (Unreal just has a lot of the nodes already created for you, both in blueprints and in the material editor, simplifying the process.)

EvanGreenwood

I thought for a moment that that explosion at the end was a 3D volume explosion... (it looked like he was moving around it)... But it looks like there is a sprite map on the floor (and so what I'm looking at is Unreal Engine creating an explosion flipbook)... And he says at the end that's the recommended thing to do (which I suppose is a nice feature, though there's better tools for this surely).

Would it be possible to render an explosion out as a volume? Do the frames it is rendering include depth/heat etc information?

Elyaradine

So, as far as I know, that actually was a volume. :D

The thing that you're seeing on the floor isn't a sprite sheet of what he had in the viewport: it was a sprite sheet that represented what the volume would look like, with each "slice" being one part of the depth. The volume is drawn 64 times (or whatever number, based on some balance between memory, overdraw(?), resolution, and your computer's power), with each frame being one slice of the volume.

As for having depth, heat, etc., he had those running in real time in his fluid sim in the last part of his talk (though it was a lengthy part and I admit I was kind of turning off at that point XD) -- you can definitely have those running at real time; the "problem", I think, is finding some balance between the size of your volume/area, and the resolution of your simulation.

He still recommends baking it to a flipbook because for 99.9% of games the perf cost wouldn't make it worth it. But if you focus your game and build it within those constraints, I don't see why you can't already make something around it with real time sims. (I think of Little Inferno as an example, where as far as I could tell their fire was a legit fluid simulation, but it was in 2D, and in a contained area. I dunno, maybe they faked it really convincingly.)

[edit] Here's his blog: http://shaderbits.com/blog/creating-volumetric-ray-marcher ...with this video (showing the volume):

EvanGreenwood

This volume rendering looks really cool... Yeah, I could tell from the video that it was running in realtime with heat and such, but it's still disappointing that computers still aren't powerful enough to do this kind of thing extensively (as apposed to in very controlled and limited demos).

There's another cloud example Ryan Bucks shows which looks amazing, but it's in a tiny cube :(



I feel like it might be possible to do a rad sky-land type game, where everything takes place in clouds in the sky with this kind of technique. Like there's opportunities for stealth in the clouds, for blowing clouds around to reveal or conceal, for dodging between clouds, for dog-fighting in clouds.

But it just doesn't seem like hardware is quite there yet, that the quality of the simulation and the density of the volume would have to be super low to run on even very powerful machines in 2017.

Though it's getting close!

I wonder if there are other experiences (besides experiences in clouds) that rely on volumes that until now have been impossible to create?

Kulu

Im Getting left in the dust again! hahahahaha . very impresive, especially the volumetric dust demo. Caged Photon would look amazing .....if i could pull these visuals off in 3D Rad. very impressed.