Name: 潛伏者的崩潰。視覺效果｜03｜特色亮點｜虛幻引擎 (Infiltrator Breakdown: Visual Effects | 03 | Feature Highlight | Unreal Engine)
Uploaded: 2021-01-14T07:04:21.000Z
Duration: 8 min 17 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

Hello and welcome to Part 3 in our series on the visual effects of the Infiltrator tech

基礎被動語態

Today we're going to take a look at the fireball effect that was seen about halfway through

Joining me is senior visual effects artist Francois Antoine.

So why don't you start by telling us a little bit about yourself.

Sure. So, before coming to Epic, I worked in film visual effects for ten years.

I'm excited about this demo today because we're going to be showing an explosion which

uses some of the same techniques that we use in film visual effects.

Can you give us an overview of what's so special about this effect?

Well, we had to create this explosion with a new technique called a volume texture and

it's basically a texture that's three-dimensional.

That in combination with GPU particles allowed us to create what we call our volume explosion.

Traditionally, sprite-based explosions don't have that cohesive feel but the volume explosion

can overcome those limitations and give the impression that it's really rolling through

The first step was to create the data for the volume explosion.

For that, I went into 3ds Max and used the FumeFX plugin to generate a 3D fluid simulation.

You can see that here we imported the geometry from Unreal Engine and are using FBX.

It actually saves the placement of all the geometry and also allows you to import camera

with the camera angle and the different lens settings.

Which I imagine would be useful here, where you need to wrap a fluid simulation around

Yes, absolutely. Actually, having the camera allows you to really customize and animate

to the camera, which can be a big time saver so you don't waste time animating things that

Once we have the explosion going, what I did is render ten cross sections of the fluid

simulation from a top down point of view.

And you can see that each of these cross sections is represented by the volume between each

So these are now rendered out, and one of the cross sections looks just like this.

And you can actually see inside the explosion right there because this is a middle cross

Alright, so once I had all of these cross sections rendered out, I brought them together

Over here as you can see on the left, I have all ten cross sections stacked on top of each

This was just a way to test to make sure that there were no rendering artifacts or shadows

And it was to make sure everything was properly sorted before bringing that information into

Now we're going to import each of these slices as a sub-UV texture.

So this is one of the bottom-most layers.

You can see the cross section for each of the frames of the render.

And I imagine this would be one of the lower slices?

As the explosion moves up, it just leaves behind smoke.

So what we could do is look at one of the higher level fireball slices.

You can see here that you have nothing in the beginning because the fireball hasn't

reached that area of the fluid simulation.

Then the top cross section is right here.

The next step is to recreate the information between each of these slices.

Here we are inside the material that we wrote.

You can see there is a node called the Volume Texture Sample and this is where we create

It is also a function; as you can see it is highlighted in blue.

A function is basically a network of nodes that can be re-used very easily, kind of like

And this was created by artists; you didn't have to bring in a coder to write this.

And that's where the power of Unreal is, is that we can actually prototype these kinds

You can see right here we have more functions.

Each of these functions references one of the slices that we rendered out earlier and

You also see there are also extra parameters here that artists can set, which is like the

XY_Size of the volume, and the space between each slice.

So a little bit of customization if you need it later?

And because these are parameters, they will be exposed to the material instance which

Very nice. OK, so you've got your material at this point - what's the next step?

The next step is to actually be able to display that volume texture.

Typically, a way to display volume texture is to ray trace it, but that is very expensive

Instead, what we are using is a point cloud of particles.

What's going to happen is that each one of these particles is going to look up a certain

point in space of the volume texture and display those color values.

I notice the particles aren't moving; we're looking at this in wire frame right now.

I guess each one of these is kind of like a static monitor?

The motion is not in the particles; it is in the texture that is actually animated.

We basically just need a lot of tiny little billboards that will sample that texture and

display it, so they aren't moving for that reason.

Right here we have about 500 GPU particles in the GPU particle system.

That's the right amount when we are kind of far from the camera, but here because we are

looking at the explosion very closely, I'm going to increase that count just for the

sake of visualizing the explosion up close.

2,000 particles is still very cheap by GPU standards.

Now we can see the explosion happening and if we go to the top view, which is where our

Oh that is amazing, you can actually feel it creeping up at the camera.

Yes, and that's exactly the feeling we wanted.

That's something we don't traditionally get with regular 2D sprite explosions because

they don't have the coherance between each other and they don't have this kind of growing

Because this is made of slices, if you switch to the side view you'll be able to see what

字幕列表影片播放

潛伏者的崩潰。視覺效果｜03｜特色亮點｜虛幻引擎 (Infiltrator Breakdown: Visual Effects | 03 | Feature Highlight | Unreal Engine)

sort

material

technique

trigger