Environmental Simulation Part 1

When I settled on the current game design idea a central piece was an environment simulation that would effect player experiences and that player choices could in turn effect - creating a feedback cycle.

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Iteration 737 - Humidity Heat Map

The goal wasn't (and still isn't) to create an environmental simulation that was "physically accurate." The goal was to create a simulation that was an abstraction of reality or at least had some of the key features seen day to day and year to year. I wanted the player to be able to alter the world around them in a way that reflects reality but that doesn't need to be 100% realistic. 

Key Features:

• Day to day temperature swings
• Seasonal temperature swings
• Wind to transport moisture
• Water/Rain cycle
• CO2 effects
• Pollution accumulation and transport
• Runs off the main thread

Building Blocks

The first step in creating the simulation was to break up the environment into a series of blocks. Each box would have it's own set of environmental variables (temperature, humidity, ground water, wind, etc). These "climate blocks" would interact with it's neighbors to create localized weather and also to allow local variances such as terrain height and cloud density to impact the weather. 

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Test Terrain with Climate Blocks

As the simulation developed and more complex interactions were add a few changes/additions to the climate blocks were needed. The first critical piece was the addition of an "atmosphere block" on top of each climate block. The atmosphere block is simulated air space above that often has a different temperature than the air on the ground/ocean. This allowed for up and down drafts that could help move clouds and cause an on or off shore wind depending on the season (more about this later).  Without an onshore wind clouds and more importantly rain rarely make it to the land.

A second key addition was the classification of terrain types. At the time of writing this the simulation is only using three types of terrain ocean, grassland and mountains. This largely controls the "target" temperature of climate block and in the case of the ocean maintains a constant saturation of ground water. Oceans have moderate target temps with smaller seasonal and daily fluctuations. Grasslands have a higher target temp than the mountains but both have larger daily and seasonal fluctuations than the ocean.

Daily and Seasonal Temperatures

Seasonal sun intensity is controlled by an animation curve that is sinusoidal in shape. Max values occurring during the "summer" and of course minimum values occurring during the "winter." A second curve was used for daily fluctuations. The curves are currently identical... That may change in the future. 

At first these curves were used and tuned to be a true energy flux with energy being added during the day and energy lost during the night. While more physically accurate and potentially allowing for more emergent weather, it also made it far more difficult to tune and balance. After significant testing and tuning this method was abandoned for a more controlled method. 

Each terrain type has a median temperature that serves as a target temperature. There are also values for seasonal and daily fluctuations of that temperature.  This means that median temperatures + seasonal flux + daily flux is roughly the high temp and likewise median temperature - seasonal flux - daily flux is roughly the low temp. Variance from this is caused by the connection of neighbors and other factors. 

One of the other factors that adds some variability is the average height of the terrain. In the real world the higher the terrain the cooler the air. To reflect this each climate block samples the terrain height at multiple points and calculates an average height. From this the median temperature is adjusted slightly. This provides variation in the climate that (hopefully) lends itself to more interesting and emergent weather.

Wind

Wind in the simulation does not  have a physical presence and is simply a Vector3 that stores the wind velocity. The wind for an individual climate block is calculated based on the temperatures of the neighboring climate blocks, including the upper atmosphere. The inclusion of the upper atmosphere allows up and down drafts which allows for onshore or offshore breezes (as mentioned above). 

To calculate the wind the simulation calculates a temperature difference between the climate block and a neighbor and then multiplies that by a vector that goes from the climate block to the neighbor. Final direction (sign) of the wind is based on blowing from hot to cold. 

The simulation sums all the winds due to neighbors to arrive at a (nearly) final wind value.

A prevailing wind is then added. This allows larger global winds to be added to create larger and different weather patterns. The strength of the prevailing wind is a tune-able variable. Current testing is with an in/out pattern that helps to blow clouds away from land in the summer. 

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An early WEather Prototype

After the prevailing wind is added the vector is normalized. There was some debate about normalizing the wind...  In the end the choice was made to keep the normalization as this meant that clouds always would have some wind. It also prevents unrealistically large or small winds that become problematic when trying to transport clouds/moisture.

The final step is a check on the vertical component of the wind. Since the upper atmosphere is often at a very different temperature it can therefore be the dominant contribution to the wind. This is a problem due to only simulating two layers of atmosphere rather than more layers or the ideal of a continuous atmosphere. Effectively the vertical component is clamped to a range between -0.5 and 0.5. This helps to keep clouds generally moving horizontally.

Additional controls are needed to avoid the clouds going too high or going through the ground. The altitude of the clouds is mostly visual as the horizontal location determines where clouds can deliver rain. Because of the this a simple min and max altitude are set. Clouds check against these values and degrees of freedom are restricted in the rigidbody to prevent clouds from going outside the bounds. Checks on vertical velocity are also necessary to allow the clouds to move away from the limits. 

Continued in Part 2

In Part 2 I'll discuss the most difficult part (so far) of the simulation that being the Water and Rain Cycle. Or more specifically the balancing of that cycle.

Building a Farming Game Loop and Troubles with Ground Water

Game #2 (still unnamed) is centered around economics and the environment. So a natural starting point (at least to me) when thinking about a game loop is farming. Yep. Farming. Does the world need another farming game? Hopefully!

A farming loop needs to allow the player to plant, harvest and sell crops. Nice and simple. Right?

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Sunflower Farm: Testing visuals for setting up simple farming.

This means that models need to be built, stores need to be coded and basic UI needs to be added. So I setup a quick and dirty (ugly) inventory that allows the collection and basic handling of items. Items are stacked for organization and stacks can be split and recombined. Nothing fancy, just enough to play test. (A good tutorial to get you started.)

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An ugly but functional inventory UI

Basic animations allow a player to dig and get some tilled soil in which to plant a crop. Crops can be added, but I didn't grab a image.

Testing of basic digging mechanics.

On top of this crops should respond to the environment. Crops should grow when the conditions are right - it doesn't make much sense for corn to sprout when it's below freezing or there's no moisture in the soil. So this means setting up each plant with ideal conditions and scripting growth. Still not too hard.

This is apparently what I think a carrot should look like... The jury is still out on this one.

Which brings me to the current struggle...

Getting a working environmental simulation was a matter of a few hours of coding - okay probably double digit hours of coding, but still a very reasonable effort.

So far the wind is working, temperatures are reasonable, seasonal changes are working, it's even multi-threaded (not coroutines!) so there's no real performance hit. All good so far.

And then comes the water cycle. Damn the water cycle!

Ground water and ocean water evaporates into clouds. Clouds move and release water as rain. Sounds easy enough, but we all know what happens when you assume things.

The problem is getting a stable amount of ground water from season to season. How fast does the water evaporate? How fast can the clouds move? How much water can the clouds hold? How fast does a cloud release its water? How quickly does water drain back into the ocean? How many hours can I spent looking at a heat map? 

Visual Feedback on ground water... 

So many variables. Each with the ability to muck up the whole simulation. I could hard code values, but then I'd lose the players ability to screw up the world... And that has to be part of the game. Its part of the real world!

So who's idea was this game anyways? Why couldn't I try to make a 2D platformer like everyone else?

A few changes, including fixing a stupid mistake, are giving me some hope. I have now seemly stabilized the lowest ground water level for a given thermal input/output. This should allow players to mess up the CO2 level and get a higher evaporation rate and thus drier soil... Or allow other season to season changes to impact crop growth. 

One change was to make the ground water flow rate respond to the amount of water in the soil. It is also a function of how many environmental cycles there are per game year. 

This basically slows the rate if the average ground water dips below 0.5 and raise the rate if it climbs above 0.5 (almost all of the environmental setting are floats between 0 and 1). Not a perfect feedback loop, but seems to help contain the crazy swings. This would seemly allow the (minimum) average ground water to be a function of ground water flow rate, evaporation and temperature. 

If I can stabilize a minimum ground water level then I should be quite a bit closer to getting a overall stable and reproducible water cycle.

Fingers crossed. 

The Inevitable : FTF PostMortem

Fracture the Flag

Fracture the Flag is my first and only game. Not the only game that I've published. It's my only game, period.

I'm pretty damn proud of FTF. Sure I had dreams of selling 100k copies or 50k copies or even 10k copies. None of which happened, but the real goal was to learn, to build a (small) community and create a game that at least some people thought wasn't total garbage.

By that measure it has been a complete and total success.

While the code base is a mess of poorly written spaghetti code it mostly works. I learned how to better organize my code and how to create more efficient code. I discovered that multiplayer is great idea, but like so many before me, I also learned it's freaking hard to implement. What works well on two test machines on my desk is very different from two players that are on opposite sides of the Atlantic. I figured out a basic workflow from Blender to Unity. I stumbled through the process of creating basic editor extensions to make my game development a little easier. I also learned I had no idea how to set up the lighting in a scene and still don't.

I learned that there is plenty more to learn.

Managing the game and community surrounding the game after the initial Early Access release was stressful, but still more rewarding than I could have expected. I had no idea how buggy the game was. Not really. I had no idea how thoughtful and kind some people would be. So many people were constantly giving feedback and helping make the product better. My biggest lesson in taking a game from Greenlight to Early Access through to Full Release is simple:

Be open. Be honest. Be human.

Folks can smell from miles away a developer that just wants a quick paycheck. While not every interaction in the FTF Steam community was positive I found most can be turned that direction with a little humility and honest listening. Not every customer has a good idea or even a valid complaint, but most do. So I did  my best to listen.

Case and point: Two friends each bought a copy of FTF hoping to play together. They quickly found several game breaking bugs that earlier players had simply ignored or hadn't noticed. These two players proceeded to rip FTF to shreds on Steam reviews - yes plural, they each wrote one. Both brutal and brutally honest. I didn't respond to the review, but when they posted in the forums I took the opportunity to start a conversation. After the exchange of several comments I had great feedback from the players and removed several sizable bugs from the code base. They dropped their negative reviews and decided not to ask for refunds. I never saw if they left positive reviews, but the huge negative reviews were gone. That's a huge win for a solo developer and worth every ounce of effort.

Fracture the Flag

Let's talking pricing.

When I first had a vision for FTF I thought surely the game must be worth $10-12. I mean I've worked so hard on it! It's got multiplayer for crying out loud. As it got closer to the Early Access release date I got a bit gun-shy. I refocused on my main goals. Making money would be nice, but it wasn't the primary goal. So I cut the price. I cut it a lot. Down to $2.99 in the US market. This seemly had the effect of lowering expectations and doing so in a helpful way.

The early reviews were incredibly positive. Early on FTF has a 90+ percent positive rating - and not from people who got free keys. The game sold reasonably well in its first week with sales continuing to trickle in as the weeks passed.

ftfsteamreviews

I fixed bugs and added features before the full release. I added so much! So many good ideas came pouring in from the community. So I decided to raise the price. To the price of a latte in Aspen... All of $4.99. Sales slowed and expectations seemed to rise while the rating on Steam dropped to what it is now, 78%. Was it a mistake?

Then came release day.

Sales were modest but better than I hoped. The first day as a full release saw almost no exposure on Steam but was still the best sales day in the short history of FTF. More copies of FTF were sold in the those first three days then in the entire first week of Early Access. Not too shabby.

I hear people say you only get one release. Maybe that's true. But I think building a community and getting positive reviews helped to serve up more sales then FTF would have seen had it jumped straight in as a full release. I know I'm more likely to buy a game that has decent reviews and has been "out" for at least a little while. But who really knows, maybe I'm just seeing what I want to see.

7 months after the initial Early Access release FTF is essentially "finished." No, it doesn't have every possible feature. Yes, there are still bugs. And no, I didn't make enough to quit my day job - not even close. Sales are generally within the margin of error shown by Steam Spy but I have often seen the numbers dip too low (but I've never seen them go too high). I made enough to easily pay for a high-end mountain bike and new set of skis and boots. For a guy who's day job requires bikes and skis... Not a bad result.

My hourly wage? Probably didn't make it to minimum wage... No, let me rephrase that. I didn't make minimum wage.

You can see sales spike on the release day and then again during sales and of course the day FTF came out of Early Access.

sales-graph

So now the game is in the long tail. Sales have slowed as expected, but the trickle is still going. At least enough to buy my wife and I dinner out once a week.

So what would I do different?

No multiplayer. While I nearly dipped my toes into that pond again for game #2, a quick read of some FTF comments reminded me of the horrors of trying to sell a multiplayer game as a solo developer. This might be a lesson I have to learn more than once...

For game #2 I want to find an outlet for early builds beyond Early Access. Find a smaller market. Find a community interested in giving feedback and more willing to take risks on a title. Take the time to polish the game before heading to Steam.

As a solo developer I need my games to be more procedural. With FTF building a level took days and the way I built the level meant I often couldn't even make small changes without completely scrapping the level and starting over. Got a rock in the wrong spot? Combined the wrong meshes and can't get good occlusion culling? Too bad.

Game #2 needs to be a game I want to play. FTF started as memories of playing Crossbows and Catapults a kid. I loved that game. Then FTF started to morph. It turned into something totally different. Sometimes for good reasons and sometimes not. It's not even close to the game I first set out to make. As a result I tried to squeeze into an already defined genre and all the expectations that came with it. Slowly, with each added feature FTF became a game I wasn't really interested in. So, now I dream of the game that I simply want to keep working on. Wouldn't that be magical?

What's next?

Game #2 is next. I have a vision, but not a complete plan. I want to create something different. (Shocking I know). I am fascinated by how poorly we treat each other as humans and how poorly we treat our beautiful planet. I dream of a game that could explore those very real issues while still being fun and challenging. In my head the game is so hopelessly over scoped I worry I may never be able to finish it or if I do it will turn to total shit.

So ignoring common sense, step one is to create a game world that I want to spend more time in...

Procedural Trees 1

I know that's ass backwards for most folk, but a world that is pleasant and enjoyable to walk around it seems like the first step in learning to appreciate that world.

The page has just begun to be built, but you can see what there is to see about #2 here.