00:07Hello and welcome back to Inside Unreal, where you can see how to make content for Unreal Engine 4.
00:13Today we're going to be continuing with Part 2 of our special feature on the visual effects that were created
00:17for the Infiltrator tech demo.
00:19Once again I'm joined by Tim Ellick, Senior Visual Effects Artist for Epic Games. Hi Tim.
00:23Hey Zach.
00:24And tell me, what are we going to be talking about today?
00:26We're going to talk a little bit more about the Depth Collision Module.
00:29We're also going to get into some water effects, and then we're going to look at some atmosphere effects for
00:33the underground section of Infiltrator.
00:35Sounds awesome. Let's get started.
00:37So to help illustrate this, I set up a custom scene here with the two particle effects that are exactly
00:43the same.
00:44And you can see the particles are both using the Depth Buffer Collision to collide with these meshes.
00:50And the Depth Buffer Collision, you can preview the actual Depth Buffer here in the buffer visualization.
00:55And if I open that up, you can see this is the information that the particle collision module uses to
01:02determine where the particles need to collide with the surface.
01:05The lighter areas are further back, and the darker areas are further up front.
01:10And if I just switch back to Lit Mode, you can see that even though these are both the same
01:15mesh...
01:16Oh, they are?
01:17They're the exact same mesh, the only thing that's different about them is the material.
01:21This is using an opaque material, while this is using a mask material.
01:25And as you saw in the Depth Buffer, the mask material writes to the buffer, so all these particles can
01:29collide and fall through the holes in the actual mask surface.
01:34So you're actually kind of poking holes in this mesh by way of the material, and the particles can fall
01:39through that?
01:40Yes.
01:40So if I take my effect and pull the emitter tab and the properties tab over here...
01:46Now these are two panels from the Cascade Particle Editor, correct?
01:50Yes, in Unreal Engine 4 you can tear the panels off and move them anywhere on the screen that you
01:54want them.
01:55And I'm just going to solo this emitter here so we can really get a good look at this.
02:00And I'm just going to increase my spawn rate to something a little crazy.
02:05So you can really see the particles falling through there.
02:08Nice.
02:08I'm going to reduce it just a little bit.
02:13So when we get into the actual collision module, there are several different options,
02:18and you can mouse over any of these to get a quick description of what it does.
02:22And so as you can see, the resilience controls how bouncy the sprite is.
02:26So if I set this to 1, the particle is just going to go crazy bouncing all over the place.
02:32And if I set it back to 0.125, it's a little bit more reasonable.
02:36And then friction is just how sticky the surface may be.
02:41So if I set it to 1, the particles are just going to really adhere to the surface.
02:45And if I set it back to 0.25, they'll slide around a little more.
02:49If I set it to 0, they'll just slide all over the place.
02:52And we can also use these radius controls to offset the sprites from the surface so that
02:58they don't just clip right into the ground so it can get them to show up just a little bit
03:04more.
03:05So it's kind of like offsetting the collision surface?
03:08Yes.
03:08And then we have the response method which determines how the particles are going to behave once they collide.
03:14You can set them to stop and they'll just stick right to the surface.
03:19Or you can set them to kill and they won't go through the surface anymore.
03:23You can see that most evidently over here.
03:26That is just too cool.
03:33Typically water is one of the more challenging effects to create.
03:37And what I try to do when I first get started is break the water down into what I consider
03:42to be the ideal forms.
03:43And in order to do that I take a look at a lot of different reference.
03:46Sometimes I look at photography but I also like to look at 2D animation like old Disney films.
03:51As well as the book Elemental Magic by Joseph Gillen which I recommend to any effects artist.
03:56And you can see here that I've broken all of this down into like the 6 parts that I felt
04:01like I needed to achieve this particular effect.
04:04This is sort of like a larger splash and then another bit of water that just sort of lifts off
04:09the surface.
04:10Then the radiating ripples as well as some different droplet shapes which I can use on sprites.
04:15And then this drop which I can use with a mesh emitter.
04:18And once I get all those things together I pull all that into Cascade.
04:22And you can see here's the final effect.
04:26And I can use the dynamic parameter and different material controls within Cascade.
04:31To manipulate the behavior of the material in time with the animation which I control on the mesh level.
04:37Can we see that in wireframe?
04:39Sure.
04:40Oh yeah that's really cool.
04:41You can see here each one of these is three dimensional.
04:44So if I rotate it around from different angles you can get a different view of it.
04:48And we can even use it in different ways.
04:50Like this particular mesh you can see looks more like if someone was a step in a big deep puddle.
04:55And it would lift up and splash out.
04:57But in order to reuse and save on memory I actually just scale the mesh a little bit different.
05:03And animate it differently here so that I can save on asset space.
05:08Now where do you see this effect in infiltrator?
05:10It's in the hallway as the soldier's making a turn walking down towards the infiltrator.
05:15And you can see it on the right hand side there.
05:17And it's one of those effects that we use just more for ambience to add some secondary animation to the
05:22world.
05:22And just help bring the world to life.
05:25You can see in the background here there's a lot of mist and haze.
05:28And this is achieved with a mixture of particle systems as well as meshes.
05:33And there's some more haze down in here just kind of drifting up through the grates.
05:37And that helps to find the mid-ground, the background, and then in the foreground we have this kind of
05:41lit smoke or fog.
05:44And then some god rays coming through the grates as well as all these little tiny dust motes floating around
05:49in the air.
05:50And you can see they just sort of parallax as you move through the space.
05:54Yeah, they add a really nice depth.
05:57And these dust motes are kind of interesting because I'm actually using a vector field to control their behavior.
06:02And this vector field is just a, it's like basically if you think about it as a grid of velocities
06:07as I move around within this space.
06:09Each one of these little lines denotes a direction that the particle is going to move in.
06:15The lit translucency also is fantastic because I can just grab this effect here.
06:21And as I drag it around the world it updates in real time with the lighting information so I no
06:26longer have to tweak a material parameter or an instance parameter.
06:29Oh yeah, that's really awesome.
06:31Now let me ask you this, as an effects artist, how has Unreal Engine 4 enabled you to create scenes
06:36like this?
06:37With the new GPU particles I really don't have to worry about my emission rates and simulation time as much.
06:44So I can emit hundreds and hundreds of these little dust motes in the air and I don't have to
06:49worry that every single one of them is ticking and updating every frame and chewing up game thread time.
06:54And I feel like these kind of details are what really helps define the space and create a relationship between
06:59the player and the world.
07:00And best of all, we do everything in Cascade so the tool is very familiar and for anyone who's used
07:06to doing effects in Unreal Engine 3,
07:08making the move to Unreal Engine 4 with Cascade is going to be pretty straightforward.
07:12Very cool. Well that's about all the time we have for today so thank you very much for your time
07:17Tim and we will see you on the next Inside Unreal.
07:20Thank you.
07:21Thank you.
07:23Thank you.
07:26Grazie a tutti.
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