# Tile Explosion for Diagonal Roads

## Recommended Posts

Roads that turn at only 90 degrees seem unnatural, but rendering 45 degree turns is turning into a major headache, because it means that roads cut diagonally across tiles and leave pieces of themselves in neighboring tiles. In addition to having textures to render all the various turns an intersections, we also need every combination of nearby roads sticking out in the corners of the tile. In total that seems to be 4096 road tiles just to cover all the possibilities, even when we restrict roads to only going tile-center to tile-center.

We can save memory by doing some flips and rotations in UV coordinates, but I estimate we'd still need dozens of tiles. We can also save some effort by making the tiles transparent beyond the edges of the road, and then layer together multiple tiles when appropriate, either in pre-processing or in the shader. Whatever we do, it is becoming a major headache for something which seems to be so simple in concept. Am I somehow approaching this problem from the wrong direction?

##### Share on other sites

I'm misunderstanding you somewhere - you are talking about "tiles" but also mentioning tiles crossing over other tiles. Are your tiles always in a uniform, non-overlapping, axis-aligned grid, or do you depart from that?

What I mean is, if you have a diagonal road like this:

I would count that as four tiles - is that how your game works?

I'm also not understanding where you are getting the number 4096 from. Recently when I was thinking about the same concept (with grid-aligned tile-based games), I calculated it as a max of 256 for automapping tiles, and for roads specifically, it was less - and if using rotations and horizontal/vertical mirroring, less still.

##### Share on other sites
46 minutes ago, Servant of the Lord said:

You are talking about "tiles" but also mentioning tiles crossing over other tiles.

Actually I meant that roads cross over neighboring tiles. The tiles are a perfectly regular, axis aligned grid as one would expect. Here's an illustration of the kind of thing I was thinking about:

Notice how when the road goes from the center tile to the bottom-left tile, it doesn't just affect those two tiles but also adds a bit of road to the center-left tile and the center-bottom tile. That's how I got to 4096, because every combination of curves and intersections has to also include every possible combination of bits of road in the corners. For example, the center tile and the center-right tile are almost identical except for a bit of road in the bottom-right corner of the center tile.

Now I see that using smaller tiles could potentially solve the problem. By chopping the road into smaller pieces, there are more ways to assemble roads from fewer pieces. The downside of this is more tiles will mean more triangles on the screen, less variety in the shape of roads, and it also turns road rendering into a jigsaw puzzle where we have to figure out how to assemble the pieces to get the road we want. One tricky point will be ensuring that diagonal roads are the same width as axis-aligned roads.

Edited by Outliner

##### Share on other sites

Ouch, that does complicate matters.

And then come back and layer the corners on top of existing tiles in a second pass:

Then, while you still have a buttload of tiles, you at least simplify it somewhat by not having to worry about the tiny corners.

e.g:

##### Share on other sites
8 minutes ago, Outliner said:

Now I see that using smaller tiles could potentially solve the problem. By chopping the road into smaller pieces, there are more ways to assemble roads from fewer pieces. The downside of this is more tiles will mean more triangles on the screen, less variety in the shape of roads, and it also turns road rendering into a jigsaw puzzle where we have to figure out how to assemble the pieces to get the road we want. One tricky point will be ensuring that diagonal roads are the same width as axis-aligned roads.

As far as the "more triangles on the screen", you could make the road pieces in smaller tiles, but then use a tool to programmatically assemble the different variations (including rotations and flippings) into the large/regular tiles.

Even poor videocards can output bajillions of triangles, though, so I wouldn't worry about having to draw a bunch of small triangles unless it actually proves to be a bottleneck. I don't know how many will be onscreen in your game, though.

A third option would be to split the tiles into 2x2 instead of 3x3:

##### Share on other sites

Why cant you just splat the roads?

##### Share on other sites
4 hours ago, h8CplusplusGuru said:

Why cant you just splat the roads?

As far as I know, splat just means having multiple textures on a mesh so we can have one texture in some places and other textures in other places by using a splat map to to define where each texture is visible. That has several issues. For one, the splat map is a raster, so it tends to pixelate unless it has hugely high resolution. For another, roads often have a direction to their texture, like the lines of a highway, or the grooves of a dirt road. I'm not aware of any way to achieve that effect with splatting.

Edited by Outliner

##### Share on other sites

Edited by h8CplusplusGuru

## Create an account

Register a new account

• 10
• 14
• 11
• 10
• 11
• ### Similar Content

• Hello fellow devs!
Once again I started working on an 2D adventure game and right now I'm doing the character-movement/animation. I'm not a big math guy and I was happy about my solution, but soon I realized that it's flawed.
My player has 5 walking-animations, mirrored for the left side: up, upright, right, downright, down. With the atan2 function I get the angle between player and destination. To get an index from 0 to 4, I divide PI by 5 and see how many times it goes into the player-destination angle.

In Pseudo-Code:
angle = atan2(destination.x - player.x, destination.y - player.y) //swapped y and x to get mirrored angle around the y axis
index = (int) (angle / (PI / 5));
PlayAnimation(index); //0 = up, 1 = up_right, 2 = right, 3 = down_right, 4 = down

Besides the fact that when angle is equal to PI it produces an index of 5, this works like a charm. Or at least I thought so at first. When I tested it, I realized that the up and down animation is playing more often than the others, which is pretty logical, since they have double the angle.

What I'm trying to achieve is something like this, but with equal angles, so that up and down has the same range as all other directions.

I can't get my head around it. Any suggestions? Is the whole approach doomed?

Thank you in advance for any input!

• By devbyskc
Hi Everyone,
Like most here, I'm a newbie but have been dabbling with game development for a few years. I am currently working full-time overseas and learning the craft in my spare time. It's been a long but highly rewarding adventure. Much of my time has been spent working through tutorials. In all of them, as well as my own attempts at development, I used the audio files supplied by the tutorial author, or obtained from one of the numerous sites online. I am working solo, and will be for a while, so I don't want to get too wrapped up with any one skill set. Regarding audio, the files I've found and used are good for what I was doing at the time. However I would now like to try my hand at customizing the audio more. My game engine of choice is Unity and it has an audio mixer built in that I have experimented with following their tutorials. I have obtained a great book called Game Audio Development with Unity 5.x that I am working through. Half way through the book it introduces using FMOD to supplement the Unity Audio Mixer. Later in the book, the author introduces Reaper (a very popular DAW) as an external program to compose and mix music to be integrated with Unity. I did some research on DAWs and quickly became overwhelmed. Much of what I found was geared toward professional sound engineers and sound designers. I am in no way trying or even thinking about getting to that level. All I want to be able to do is take a music file, and tweak it some to get the sound I want for my game. I've played with Audacity as well, but it didn't seem to fit the bill. So that is why I am looking at a better quality DAW. Since being solo, I am also under a budget contraint. So of all the DAW software out there, I am considering Reaper or Presonus Studio One due to their pricing. My question is, is investing the time to learn about using a DAW to tweak a sound file worth it? Are there any solo developers currently using a DAW as part of their overall workflow? If so, which one? I've also come across Fabric which is a Unity plug-in that enhances the built-in audio mixer. Would that be a better alternative?
I know this is long, and maybe I haven't communicated well in trying to be brief. But any advice from the gurus/vets would be greatly appreciated. I've leaned so much and had a lot of fun in the process. BTW, I am also a senior citizen (I cut my programming teeth back using punch cards and Structured Basic when it first came out). If anyone needs more clarification of what I am trying to accomplish please let me know.  Thanks in advance for any assistance/advice.

• The more you know about a given topic, the more you realize that no one knows anything.
For some reason (why God, why?) my topic of choice is game development. Everyone in that field agrees: don't add networked multiplayer to an existing game, you drunken clown.
Well, I did it anyway because I hate myself. Somehow it turned out great. None of us know anything.
Problem #1: assets
My first question was: how do I tell a client to use such-and-such mesh to render an object? Serialize the whole mesh? Nah, they already have it on disk. Send its filename? Nah, that's inefficient and insecure. Okay, just a string identifier then?
Fortunately, before I had time to implement any of my own terrible ideas, I watched a talk from Mike Acton where he mentions the danger of "lazy decision-making". One of his points was: strings let you lazily ignore decisions until runtime, when it's too late to fix.
If I rename a texture, I don't want to get a bug report from a player with a screenshot like this:

I had never thought about how powerful and complex strings are. Half the field of computer science deals with strings and what they can do. They usually require a heap allocation, or something even more complex like ropes and interning. I usually don't bother to limit their length, so a single string expands the possibility space to infinity, destroying whatever limited ability I had to predict runtime behavior.
And here I am using these complex beasts to identify objects. Heck, I've even used strings to access object properties. What madness!
Long story short, I cultivated a firm conviction to avoid strings where possible. I wrote a pre-processor that outputs header files like this at build time:
namespace Asset { namespace Mesh { const int count = 3; const AssetID player = 0; const AssetID enemy = 1; const AssetID projectile = 2; } } So I can reference meshes like this:
renderer->mesh = Asset::Mesh::player; If I rename a mesh, the compiler makes it my problem instead of some poor player's problem. That's good!
The bad news is, I still have to interact with the file system, which requires the use of strings. The good news is the pre-processor can save the day.
const char* Asset::Mesh::filenames[] = { "assets/player.msh", "assets/enemy.msh", "assets/projectile.msh", 0, }; With all this in place, I can easily send assets across the network. They're just numbers! I can even verify them.
if (mesh < 0 || mesh >= Asset::Mesh::count) net_error(); // just what are you trying to pull, buddy? Problem #2: object references
My next question was: how do I tell a client to please move/delete/frobnicate "that one object from before, you know the one". Once again, I was lucky enough to hear from smart people before I could shoot myself in the foot.
From the start, I knew I needed a bunch of lists of different kinds of objects, like this:
Array<Turret> Turret::list; Array<Projectile> Projectile::list; Array<Avatar> Avatar::list; Let's say I want to reference the first object in the Avatar list, even without networking, just on our local machine. My first idea is to just use a pointer:

Avatar* avatar; avatar = &Avatar::list[0]; This introduces a ton of non-obvious problems. First, I'm compiling for a 64 bit architecture, which means that pointer takes up 8 whole bytes of memory, even though most of it is probably zeroes. And memory is the number one performance bottleneck in games.
Second, if I add enough objects to the array, it will get reallocated to a different place in memory, and the pointer will point to garbage.
Okay, fine. I'll use an ID instead.
template<typename Type> struct Ref { short id; inline Type* ref() { return &Type::list[id]; } // overloaded "=" operator omitted }; Ref<Avatar> avatar = &Avatar::list[0]; avatar.ref()->frobnicate(); Second problem: if I remove that Avatar from the list, some other Avatar will get moved into its place without me knowing. The program will continue, blissfully and silently screwing things up, until some player sends a bug report that the game is "acting weird". I much prefer the program to explode instantly so I at least get a crash dump with a line number.
Okay, fine. Instead of actually removing the avatar, I'll put a revision number on it:
struct Avatar { short revision; }; template<typename Type> struct Ref { short id; short revision; inline Type* ref() { Type* t = &Type::list[id]; return t->revision == revision ? t : nullptr; } }; Instead of actually deleting the avatar, I'll mark it dead and increment the revision number. Now anything trying to access it will give a null pointer exception. And serializing a reference across the network is just a matter of sending two easily verifiable numbers.
Problem #3: delta compression
Which by the way is here: gafferongames.com
As I set out to implement my own version of Glenn's netcode, I read this article, which details one of the biggest challenges of multiplayer games. Namely, if you just blast the entire world state across the network 60 times a second, you could gobble up 17 mbps of bandwidth. Per client.
Delta compression is one of the best ways to cut down bandwidth usage. If a client already knows where an object is, and it hasn't moved, then I don't need to send its position again.
This can be tricky to get right.

The first part is the trickiest: does the client really know where the object is? Just because I sent the position doesn't mean the client actually received it. The client might send an acknowledgement back that says "hey I received packet #218, but that was 0.5 seconds ago and I haven't gotten anything since."
So to send a new packet to that client, I have to remember what the world looked like when I sent out packet #218, and delta compress the new packet against that. Another client might have received everything up to packet #224, so I can delta compress the new packet differently for them. Point is, we need to store a whole bunch of separate copies of the entire world.
Someone on Reddit asked "isn't that a huge memory hog"?
No, it is not.
Actually I store 255 world copies in memory. All in a single giant array. Not only that, but each copy has enough room for the maximum number of objects (2048) even if only 2 objects are active.
If you store an object's state as a position and orientation, that's 7 floats. 3 for XYZ coordinates and 4 for a quaternion. Each float takes 4 bytes. My game supports up to 2048 objects. 7 floats * 4 bytes * 2048 objects * 255 copies = ...
14 MB. That's like, half of one texture these days.
I can see myself writing this system five years ago in C#. I would start off immediately worried about memory usage, just like that Redditor, without stopping to think about the actual data involved. I would write some unnecessary, crazy fancy, bug-ridden compression system.
Taking a second to stop and think about actual data like this is called Data-Oriented Design. When I talk to people about DOD, many immediately say, "Woah, that's really low-level. I guess you want to wring out every last bit of performance. I don't have time for that. Anyway, my code runs fine." Let's break down the assumptions in this statement.
Assumption 1: "That's really low-level".
Look, I multiplied four numbers together. It's not rocket science.
Assumption 2: "You sacrifice readability and simplicity for performance."
Let's picture two different solutions to this netcode problem. For clarity, let's pretend we only need 3 world copies, each containing up to 2 objects.
Here's the solution I just described. Everything is statically allocated in the .bss segment. It never moves around. Everything is the same size. No pointers at all.

Here's the idiomatic C# solution. Everything is scattered randomly throughout the heap. Things can get reallocated or moved right in the middle of a frame. The array is jagged. 64-bit pointers all over the place.

Which is simpler?
The second diagram is actually far from exhaustive. C#-land is a lot more complex in reality. Check the comments and you'll probably find someone correcting me about how C# actually works.
But that's my point. With my solution, I can easily construct a "good enough" mental model to understand what's actually happening on the machine. I've barely scratched the surface with the C# solution. I have no idea how it will behave at runtime.
Assumption 3: "Performance is the only reason you would code like this."
To me, performance is a nice side benefit of data-oriented design. The main benefit is clarity of thought. Five years ago, when I sat down to solve a problem, my first thought was not about the problem itself, but how to shoehorn it into classes and interfaces.
I witnessed this analysis paralysis first-hand at a game jam recently. My friend got stuck designing a grid for a 2048-like game. He couldn't figure out if each number was an object, or if each grid cell was an object, or both. I said, "the grid is an array of numbers. Each operation is a function that mutates the grid." Suddenly everything became crystal clear to him.
Assumption 4: "My code runs fine".
Again, performance is not the main concern, but it's important. The whole world switched from Firefox to Chrome because of it.
Try this experiment: open up calc.exe. Now copy a 100 MB file from one folder to another.

I don't know what calc.exe is doing during that 300ms eternity, but you can draw your own conclusions from my two minutes of research: calc.exe actually launches a process called Calculator.exe, and one of the command line arguments is called "-ServerName".
Does calc.exe "run fine"? Did throwing a server in simplify things at all, or is it just slower and more complex?
I don't want to get side-tracked. The point is, I want to think about the actual problem and the data involved, not about classes and interfaces. Most of the arguments against this mindset amount to "it's different than what I know".
Problem #4: lag
I now hand-wave us through to the part of the story where the netcode is somewhat operational.
Right off the bat I ran into problems dealing with network lag. Games need to respond to players immediately, even if it takes 150ms to get a packet from the server. Projectiles were particularly useless under laggy network conditions. They were impossible to aim.
I decided to re-use those 14 MB of world copies. When the server receives a command to fire a projectile, it steps the world back 150ms to the way the world appeared to the player when they hit the fire button. Then it simulates the projectile and steps the world forward until it's up to date with the present. That's where it creates the projectile.
I ended up having the client create a fake projectile immediately, then as soon as it hears back from the server that the projectile was created, it deletes the fake and replaces it with the real thing. If all goes well, they should be in the same place due to the server's timey-wimey magic.
Here it is in action. The fake projectile appears immediately but goes right through the wall. The server receives the message and fast-forwards the projectile straight to the part where it hits the wall. 150ms later the client gets the packet and sees the impact particle effect.

The problem with netcode is, each mechanic requires a different approach to lag compensation. For example, my game has an "active armor" ability. If players react quick enough, they can reflect damage back at enemies.

This breaks down in high lag scenarios. By the time the player sees the projectile hitting their character, the server has already registered the hit 100ms ago. The packet just hasn't made it to the client yet. This means you have to anticipate incoming damage and react long before it hits. Notice in the gif above how early I had to hit the button.
To correct this, the server implements something I call "damage buffering". Instead of applying damage instantly, the server puts the damage into a buffer for 100ms, or whatever the round-trip time is to the client. At the end of that time, it either applies the damage, or if the player reacted, reflects it back.
Here it is in action. You can see the 200ms delay between the projectile hitting me and the damage actually being applied.

Here's another example. In my game, players can launch themselves at enemies. Enemies die instantly to perfect shots, but they deflect glancing blows and send you flying like this:

Which direction should the player bounce? The client has to simulate the bounce before the server knows about it. The server and client need to agree which direction to bounce or they'll get out of sync, and they have no time to communicate beforehand.
At first I tried quantizing the collision vector so that there were only six possible directions. This made it more likely that the client and server would choose the same direction, but it didn't guarantee anything.
Finally I implemented another buffer system. Both client and server, when they detect a hit, enter a "buffer" state where the player sits and waits for the remote host to confirm the hit. To minimize jankiness, the server always defers to the client as to which direction to bounce. If the client never acknowledges the hit, the server acts like nothing happened and continues the player on their original course, fast-forwarding them to make up for the time they sat still waiting for confirmation.
Problem #5: jitter
My server sends out packets 60 times per second. What about players whose computers run faster than that? They'll see jittery animation.
Interpolation is the industry-standard solution. Instead of immediately applying position data received from the server, you buffer it a little bit, then you blend smoothly between whatever data that you have.
In my previous attempt at networked multiplayer, I tried to have each object keep track of its position data and smooth itself out. I ended up getting confused and it never worked well.
This time, since I could already easily store the entire world state in a struct, I was able to write just two functions to make it work. One function takes two world states and blends them together. Another function takes a world state and applies it to the game.
How big should the buffer delay be? I originally used a constant until I watched a video from the Overwatch devs where they mention adaptive interpolation delay. The buffer delay should smooth out not only the framerate from the server, but also any variance in packet delivery time.
This was an easy win. Clients start out with a short interpolation delay, and any time they're missing a packet to interpolate toward, they increase their "lag score". Once it crosses a certain threshold, they tell the server to switch them to a higher interpolation delay.
Of course, automated systems like this often act against the user's wishes, so it's important to add switches and knobs to the algorithm!

Problem #6: joining servers mid-match
Wait, I already have a way to serialize the entire game state. What's the hold up?
Turns out, it takes more than one packet to serialize a fresh game state from scratch. And each packet may take multiple attempts to make it to the client. It may take a few hundred milliseconds to get the full state, and as we've seen already, that's an eternity. If the game is already in progress, that's enough time to send 20 packets' worth of new messages, which the client is not ready to process because it hasn't loaded yet.
The solution is—you guessed it—another buffer.
I changed the messaging system to support two separate streams of messages in the same packet. The first stream contains the map data, which is processed as soon as it comes in.
The second stream is just the usual fire-hose of game messages that come in while the client is loading. The client buffers these messages until it's done loading, then processes them all until it's caught up.
Problem #7: cross-cutting concerns
This next part may be the most controversial.
Remember that bit of gamedev wisdom from the beginning? "don't add networked multiplayer to an existing game"?
Well, most of the netcode in this game is literally tacked on. It lives in its own 5000-line source file. It reaches into the game, pokes stuff into memory, and the game renders it.
Just listen a second before stoning me. Is it better to group all network code in one place, or spread it out inside each game object?
I think both approaches have advantages and disadvantages. In fact, I use both approaches in different parts of the game, for various reasons human and technical.
But some design paradigms (*cough* OOP) leave no room for you to make this decision. Of course you put the netcode inside the object! Its data is private, so you'll have to write an interface to access it anyway. Might as well put all the smarts in there too.
Conclusion
I'm not saying you should write netcode like I do; only that this approach has worked for me so far. Read the code and judge for yourself.
There is an objectively optimal approach for each use case, although people may disagree on which one it is. You should be free to choose based on actual constraints rather than arbitrary ones set forth by some paradigm.

• An original fantasy RP game needs dedicated, self-motivated, and chill individuals! We have a story and general plot already set up, ready to be expanded upon.

Miasma: Twilight Decree is a 2D roleplay adventure game. It’s set in a unique fantasy world with a vast map containing continents and oceans alike. Players are given one objective: to endure the troublous environments Allagia have to offer and successfully progress through time to reach the Age of Technology. The stakes are high, and every character’s actions can alter the world – or reset everything back to the beginning ages. MTD features a blend of survival aspects, dark themes, with the ability to make a mark in the history books.

What we're currently looking for:

• Writers - Super creative individuals who have experience in lore-making, world-building, and know their way around fantasy writing. All of the general elements are here [setting, plot, etc.] and need some "fluffing out"[quest lines, clans/ factions/ families, etc.]. Bonus points to those who can whip up spells and skills.
• Artists - Mainly those who specialize in pixelated art, or people who can make concept art [since we lack pictures].
• Project Manager - Someone who is organized and can keep this project on the rails. As thorough as I am, it's difficult to cover all the bases on my own.
• Other Positions - Anything else to fill in the gaps. We currently use Wikidot for our wiki; someone with CSS and syntax experience to polish it up would be awesome. A musician/ composer for all things musical. Way later down the road, we'll need community managers, DMs, and the such, though it isn't necessary at the moment.

Other information:

I've been working on this project since the beginning of 2017 with a group of friends. Life basically prohibited a lot of us from continuing on with it, and it went on hiatus for a while. I'm making an attempt to bring this back from the dead since plenty of time and effort went into it beforehand. It goes without saying that I also have a passion for roleplaying.

I cannot stress enough that anyone interested should be into fantasy settings or D&D. Otherwise, you're probably not going to have fun with helping!

We do have a Patreon with a few supporters, and Discord. Until things really start moving, we'll be using Discord to collaborate.