Posts Tagged ‘engine’

Animation of the Artillery

Artillery of WinThatWar!

Original : Fisher Body craftmen

The animation of the vehicles is a perfect blend of handmade animation and procedural animation. I would like to begin with the latter type of animation, and here are the related elements:

> The movement of the vehicle is supported by the physical engine of the game. In this way, the vehicle follows the inclination of a virtual grid, a collision volume or, more simply, a deformed plan simulating the relief of the ground.

> The Artillery also needs to be able to shoot from different ranges and angles. Thus, the articulations related to the rotation of the cannon are animated by the code (what we call the “logic”) so that the shot adjusts itself directly to the position of the target, according to the position of the Artillery.

> The caterpillar tracks are also animated, following the movement of the vehicle. This effect is obtained by dynamically moving the UV coordinates of the model, in game, in accordance with the speed of the vehicle.

As a reminder, the UV coordinates are the correspondence between 3D coordinate (xyz) and 2D (uv) used to indicate where and how the textures are “drawn” on the model. In the case of the tracks, we could say that the UV “glide” on the 3D, giving an impression of rolling movement.

Artillery caterpillar continuous track

All the other animations are handled beforehand by the animator.

The animator is free to use all the other articulations available, except for the 2 articulations handled by the engine that we addressed earlier: the horizontal rotation of the turret and the vertical lifting of the cannon.

In the case of the Artillery, here are the elements created “by hand”, before the “logic” steps in:

> The animation of the installation. The vehicle is rather slow to get into siege position, and conveys the impression of a powerful weapon, which takes time to set up but is destructive. The disassembly is, however, much more short.

> Creation of shock absorption and a wave that shakes the whole vehicle when the Artillery shoots. This animation is achieved through the lifting of the mudguards, which is then synchronised with a shockwave effect, creating dust clouds.

animation joints and curves

And now, about shooting. This is when we add the particle effect which helps materialise the projectile, in the form of a plasma ball.

Finally, the death animation of the Artillery is simulated using the physical engine, called Mass FX. It is pre-calculated with the 3D modeling software and then reworked by the animator to get the desired result.

This animation goes with a smoke cloud and fragments spraying all around the vehicle. The destruction of the Artillery, alone, is not impressive enough to the player:

dislocation

This is pretty much the life of the Artillery. From the moment it leaves the factory to its death of the battle field.

This post about animation is the first half of a two-part article. The next post will be entirely dedicated to the Sound Design of the Artillery which, as you will see, is directly related to the different animations addressed here.

About RTS engine determinism

Hi everyone!

This week I’ll write about a topic which may seems a little bit austere, but truth is that it can easily become quite fun: testing

How to test a game?

When we talk about test, it may refer to several things. In the case of WinThatWar!, we distinguish three test levels:

  • unit test
  • integration test
  • test in real conditions

Test in real conditions

Let’s start with the last one, it’s the simplest: the best way to test a game is obviously to play it. It allows you (and me also) to find out unexpected issues, not only bugs, but problem of use as well (ergonomy, feeling, gameplay possibilities…)
When you’re coding a game, you can’t stop telling yourself that you really need to improve it and you forget to play it “seriously”. That’s why, at Insane Unity, we schedule regular test sessions of WTW, that we intensified when the release is about to come out.

The problem is, after a while, we know the game really well, we play the same way again and again by force of habit, and because of that we’re becoming unable to hit the broad side of a barn. That’s why we are constantly looking for new users. Newbies allow us to easily find out ergonomy issues and to make a game which will really be easy to play. Talented RTS gamers allow us to estimate how hard to master is the game, and they bring out balancing issues and the efficiency level of the interface.

Once again, I take this opportunity to thank you all, all the alpha-testers. If you weren’t there to help us improving the game, WinThatWar! would be of a much lower quality than it is today. That’s your game too!

IMG_20150523_121101

 

Unit test

Unit test responds to a very simple problem: not to go round and round in circles everytime you’re coding something, undoing what was already working.

Before comitting any change in the code, the developer have to execute tests that will check if every module’s basic fonctionnalities work well. For example, some path-finding tests check that two groups of units can cross without striking each other, some others exist to check that our maths library’s convertion functions produce the expected result, etc.

Generally speaking, a unit test is written BEFORE coding the function it will satisfy. It’s called TDD.  This is one of the fundamental practices of agile development. Unit tests are very useful to “re-factorize” the code, in other words to deeply overhaul it without changing its functionality, in order to get it ready for the add of a new feature, or to make it simpler and less subject to bugs.

If a dev ever commit a change that “broke” one of these tests (called regression), he received an e-mail from our buddy Tim (that’s the name of our integration server) that gently insults him, and keeps doing so as long as the problem isn’t solved.

 

Integration test

Finally, the integration test takes place between the two other kind of tests I just wrote about. While unit test limits itself to test a module, integration test consists, as the name suggests, on making all the modules working together.

At Insane Unity, that means make 4 AI playing in 2vs.2 every night. Here again, Tim is in charge. Forward, we’ll check that we meet the expected balancing (for example, that AI lvl 5 always beat AI lvl3 in less that 10min.) But, for now, we’re using these tests for two things:

  • check there is no crash during the game
  • make sure our simulation is desterminist

 

RTS engine determinism

Determinism, WTH is that? Once again IT engineer gibberish…actullay a program is called determinist if it provides the same result every time it’s launch with the same starting conditions. It may sounds a bit “dumb”, but that’s not that simple. When you launch a program twice in a row on a modern computer, that’s never exactly the same starting state. So, if you ask your computer to do several things at the same time, it can choses, on its own, to launch the tasks in a different order every single time.

So what? Is that really a serious problem? Yes! When two players launch a RTS game, the world state isn’t sent by the network: it would take too long. Instead, we just send every player’s commands. Starting with exactly the same initial situation, and if we apply the exact same order, at the very same time, every players actions, we manage to keep exactly the same state, the same “reality” on every device.
But here it is, if one of the computer choses to execute the operations in a different order, the reality of every player will start to split, and that where the troubles start.

The first  versions of WinThatWar! were massively using parallelism to take part of the molticore modern processors. We quickly realised theses kinds of optimizations didn’t get on well with the network mode of the game. If you want to explore further, you can read this excellent article about Age Of Empire.

So, from now on, everytime we use multithreading, we have to make sure the operations order have no impact on the final result. And how to be really sure about that? Of course, we asking Tim for help! I told you that Tim plays WinThatWar! every night, at a rate of ten per night. That’s not all: it plays every game twice in a row, starting from the same seed and checking that every step of the world simulation is exactly in the same situation during both of the two games.

From now on, if you test a LAN pre-version of WinThatWar! with some of your mates, and if you suffer a crash, be curious and go get the log.txt file to watch it’s written on it. Now, you should know what that “Simulation out of sync!” message means. 😉

Etham

Missing ingredient

Today, what about a cooking class ?
No, no, ok , we were just kidding.

A post about video games’ main ingredients sounds better to you? We’re not pretending that we know a magic solution, if so we would already had released Win That War! for good and sold 3 millions of copies in only 2 weeks…I guess.

Well, let’s see. What did we not mention yet and which could make an important difference when you spend a lot of time playing a game ? We already wrote about game-design, game-logic, gameplay (and all these words starting with “game”), game engine, 3D, biomes, pathfinding… So what is it about today ?

Any idea ?

Untitled design (1)

Of course :
Music and sound effects.

Two freelances musicians are working on these.  Cid is in charge of the sound environment of the game, inspired by the mid-21st century ‘s musics with a little touch of “pizzazz” to make it more modern. And Jean-Phi creates sound effects : construction, destruction, explosion…he draws in various references to then produce sound elements that not only fit to Win That War! universe, but should also not get the player bored or bothered even after several hours playing the same game. A matter of balance.

Wwise

The technology used is called Wwise. It’s a fabulous tool which is “artist driven”. Basically that means programmers only have to put events in the code (like “a tank explodes”, “the menu closes”…) and the musicians can choose how to mix sounds together, based on these events, without having a line of code to write. This allows us to do spatial positioning 7.1, but also procedural music based on scores that combine with each others to fit the intensity of gameplay. And that’s really cool.

And finally, here is a little video for you.

Physics!

Hi everyone!

It’s been a while since the last time I wrote on this blog. But you might be happy to know I worked on our brand new network layer…which actually works pretty well. But shhh, it’s Top Secret for now! You could give it a try when we’ll release the next Alpha.

Physics simulation, alright…but why?

Last week, I refactored the physics engine. In this old post, as a bonus in the video, you already had a quick survey of the WTW physics simulation. But, well, let starts from the beginning…what’s the purpose of this ?

In video games, physics simulation gives some substance to the objects, it avoids permeation/interpenetration: tables are put on the floor,  characters are stopped by the walls etc. In Win That War!, there are lots and lots of vehicles moving together on a field. I first developed the engine for this purpose: handle thousands of vehicles controllers. No spectacular effects, dynamics or debris yet. All of those will come later on! I was greatly influenced by the excellent “Bullet“, which is an OpenSource library, in addition of being well-functioning.

Here is an overview of Insanity Physics functioning:

Insanity.Physics-Overview

First, you fill the physical scene with objects: obstacles and vehicle controllers. The simulation is iterative and runs 60 times per second. The AI (path-finding) gives  speed related orders to the vehicles. The first step consists of detecting collisions between objects, that is to say, finding contact points. Then, the “Contact Solver” will correct speeds to minimize interpenetration between objects. The cars brake to avoid crashing into each other. For each contact point, I apply an impulse to repel both objects. If a whole group collides, the solver converges to a state in which interpenetration is lowered to the minimum for each group member. After speeds are corrected, we can compute the new positions and we can move on to the next iteration.

The collision detection is the most complicated part of the simulation:

Insanity.Physics.Collision-Overview

 

 

It is separated in two phases (Broad and Narrow). The Broad phase’s goal is to find potentially touching objects pairs. We approximate every object with a simple box to simplify tests. If two boxes cover each other, the objects might be colliding. This is the most time consuming part of the simulation. A “naive” Broad phase would consist of running every possible test, that means a million tests for 1000 objects (O(n²) complexity), which is too long. Many Broad phases algorithms do exist, especially  “Sweep and Prune” (SAP) which is used in most of physics engines.  Once potentially colliding pairs are found, the Narrow phase starts testing  if the real objects inside those boxes are actually colliding or not and find the potential contact spots. It is generally a group of algorithms. It is really easy to find the intersection between 2 spheres but when it comes to boxes and a field, something else is needed… that’s why I use XenoCollide for complex tests.

Finally, the engine’s last objective: geometrical requests. At any given time it is possible to cast a ray in the physical scene and check which objects it touches. This is generally used for a selection done by using a mouse. It is also possible to ask for everything that intersects with any convex shape. Concerning the missiles explosion, a sphere dedicated request is used.

To conclude, here is a video showing the physics’ debug drawing. As you can see it works pretty well, even with more than a thousand units!

In this video, you can easily see the broadphases boxes in red, the collision shapes in white (only sphere for the vehicles), and the terrain shape in yellow. To position the vehicles on the fields, we’re using ray casts which appear as red lines on the video, it’s also used to determine if the engineers are able to construct things. The debug display makes the video slowing down, that’s why you can see it jolts at the beginning.

That’s it for today!

Doom

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