Justine Pouyez shared some tips on the production of visual effects in Unreal Engine 4.
Introduction
Hello, my name is Justine Pouyez, I’m a french student at University Paris 8, in Arts and Images Technologies (or AIT). I’m in my graduate year of school. I’m also a VFX Artist at Kylotonn Racing games, in Paris, to achieve my formation. ATI is a formation with a lot of courses for real time, but also for cinema: animation, VFX, programming (C++, C#, Python), modeling, rendering… We have a lot of masterclass to enlarge our point of view. Two years ago, I made an internship in VFX at Persistant Studio, which are the creators of Popcorn FX. After that, I knew I wanted to make VFX. I made a lot of projects in this formation, especially little video games. Now, for my last year, I’m writing a dissertation about weather effects in video games, and to do that I created a game with my classmates with a dynamic weather system.
So how does a weather system in the UE4 game look like? What are the things you should have to have your system running?
With my researches, I decide to make a weather changer tool. To do that, I made a blueprint. At the beginning, I wanted three different weather: rain, snow and some sand storms. So I made three particles systems, with a lot of parameters, to change everything: intensity, color… That’s really the core of my tools, but it’s not enough. To have a really cool render for weather, we need to tweak fog, materials, and posts processes, so I have added some features to change that.
What are the elements that help to create the rain effect?
For the rain, I recommend you this article from Sebastien Lagarde who worked on Remember Me. It’s a very helpful and very detailed article. For the rain we use GPU particles with some materials with refraction. It’s a bit expensive but it’s not the only way to do this kind effect. Some games use just a simple material or even texture on the camera. One thing I like is making some splashing water on the ground. To do this I don’t use a collision event, it’s too huge and it collides with every meshes on the scene. I just add some splash with a little texture made in Houdini and just spawn on the ground. Recently, I saw that in another way to think rain effect. You can do a culling and just show the particles around the character. In that way, you may increase your game performances.
How do you mix the rain with the wetness and the effects of the environment itself?
I wanted a tool that controls everything, so I made it so that it can also change the ground. For example, for our game, the ground has a lot of textures, and everything is managed by parameters and lerp function. When rain is activated, a mask makes appear some puddles. We create a material function to do this, and we wet the ground thanks to roughness. We worked on a normal puddle to make some ripples when rain is active on our tools.
What way do you think you can achieve a more realistic weather effect in UE4?
One thing I learnt with my researches: realistic doesn’t mean photorealistic. To make realistic weather, you have to understand that everything in the scene changes with the weather, not only the particles. But in real life, changes are slow, so you have to make some blend effect and change values slowly. Like the fog, we change the color of an intermediate value. When it’s snowing, we change the color to blue and when it stops, the color goes to the white color slowly. And it’s the same thing for all the values we have for our tool.
What way do you work with snow?
I love snow. It makes some really cool scenes, and cool materials. The system particle is really simple. It’s just snowflakes with vector field to add some turbulence. Unlike rain, these particles collide with the ground and other objects. When they collide, they lost all their velocity. No speed, no bounces.
But particles don’t work alone, if you want a good scene, you have to change your fog, the color, and density. And of course, you have to change your materials. For the ground, I made a blend texture to change ground to a snow texture. The parameter is managed by the tools. We do the same thing for some mesh. We blend the texture and let’s appear some snow on the top.
Last thing I want to make is a particle system more realistic with more control and random on the velocity
What way would you advise approaching heat in a game?
I tried for our game to make a sand storm. For this, I used a particle system with smoke sprite. I didn’t want to make a huge particle system for smoke to cover the arena. I want to limit the number of particles and overdraw. So like other particles systems, it’s attached to the character. I made a zone around him, and spawn particles on it with some velocity. We made some changes in the fog. We made a stronger value for density to limit the point of view and change the color to something orange, red. One last thing, I modify the post process to change the color of the scene and made something more heater than usual.