106 lines
4.3 KiB
Markdown
106 lines
4.3 KiB
Markdown
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Moonfall is the name of a game engine that I spent several months developing back in 2008. It leveraged SDL for
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graphics, Lua for in-game scripting, and wxWidgets for the built-in developer tools. The cross-platform engine was
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written using the Code::Blocks IDE, but Visual Studio project files are also available.
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The game was partially inspired by [Harvest Moon](http://en.wikipedia.org/wiki/Harvest_Moon_%28video_game%29) for the
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Super Nintendo and [When They Cry](http://en.wikipedia.org/wiki/Higurashi_When_They_Cry) by [07th
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Expansion](http://en.wikipedia.org/wiki/07th_Expansion). The protagonist is a city dweller, who upon inheriting a small
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farm from a distant relative, decides to try his hand in agriculture. He finds the residents of the nearby small town a
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friendly bunch, but something about them does not seem right. Everyone is appears to be hiding something from the
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player, who must uncover the truth to survive. In short, this is (as I have described it to my friends), "Harvest Moon
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with Murder."
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## Technology ##
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From a technical point of view, the game engine was an exercise in creating a completely data driven game. In
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retrospect, it was probably over-engineered, but in general it was flexible and I liked what I could do with it. At the
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core of the engine was the `Actor` class, the functionality of which could be expanded through add-on properties. The
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property definitions were specified in XML; for example, below is the definition for the playable character:
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```
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<Actor alias = "Player.01" dynamic = "1" layer = "4" thumbnail = "Player.01.Idle.S.01">
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<Properties>
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<Animation />
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<Script resource = "Player.01.Default" />
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<Physics />
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</Properties>
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</Actor>
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```
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In addition to the self-explainable `Animation` and `Physics` properties, you can see a `Script` node which associates a
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Lua script with the actor. Scripts would get notifications about events such as `OnActorUpdate`, during which custom
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processing could take place:
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```
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function OnActorUpdate(elapsed)
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if InputIsKeyTriggered(META_KEY_USE) then
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DoActorUse()
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return
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elseif InputIsKeyPressed(META_KEY_UP) then
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DoActorWalk(DIRECTION_NORTH)
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return
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elseif InputIsKeyPressed(META_KEY_DOWN) then
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DoActorWalk(DIRECTION_SOUTH)
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return
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elseif InputIsKeyPressed(META_KEY_LEFT) then
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DoActorWalk(DIRECTION_WEST)
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return
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elseif InputIsKeyPressed(META_KEY_RIGHT) then
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DoActorWalk(DIRECTION_EAST)
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return
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end
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DoActorIdle(playerDirection)
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end
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```
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Scripts can directly interact with properties on the parent `Actor` and can communicate with surrounding world via a
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messaging system. This made it possible to build any game object imaginable by editing a couple of XML files and some
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simple scripting.
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```
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function DoActorWalk(direction)
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if playerAction == ACTION_WALK and playerDirection == direction then
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return
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end
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ActorPhysicsSetVelocity(playerId, playerWalkVelocities[direction])
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ActorAnimationSet(playerId, playerWalkAnimations[direction])
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ActorAnimationPlay(playerId, true)
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playerDirection = direction
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playerAction = ACTION_WALK
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end
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function DoActorUse()
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actorsIds = ActorPhysicsQueryShapeCollisions(
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playerId,
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ACTOR_SHAPE_TYPE_COLLISION_INTERACT
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)
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for i, v in ipairs(actorsIds) do
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ActorScriptSendMessage(v, "interact", { user = playerId })
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end
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end
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```
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I eventually stopped work on Moonfall due to a lack of time, combined with the fact that I am not an artist and could
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not author the assets required to develop this into a complete game.
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## Screenshots ##
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[](https://foosoft.net/projects/moonfall/img/gameplay.png)
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[](https://foosoft.net/projects/moonfall/img/sprite-editor.png)
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[](https://foosoft.net/projects/moonfall/img/console.png)
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[](https://foosoft.net/projects/moonfall/img/asset-editor.png)
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[](https://foosoft.net/projects/moonfall/img/map-editor.png)
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## License ##
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GPL
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