Intrinsic Programming by Erik Schulz

After a break from game development and finishing a work project in F#, I'm back and it's time for me to leave XNA behind and move on to a collection of specifically designed libraries. For my graphics engine I'm choosing ORGE by way of MORGE a .NET wrapper for it.

After digging into the C# SDK I figured a good start would be porting MorgeForm. To get this code to run install the SDK, create a project, set it to .NET 2.0, add a reference to Mogre_d (C:\MogreSDK\bin\Debug) and set the working directory to C:\MogreSDK\bin\Debug. The sample pulls resources through relative paths so you need to run in the SDK Debug directory.

On a side note I need to make my own custom theme for better syntax highlighting.

open System
open System.Windows.Forms
open System.Drawing

open Mogre

type OgreWindow(origin, hWnd) =
    //----------------------------------------------------- 
    // 1 enter ogre 
    //----------------------------------------------------- 
    let root = new Root()

    do  //----------------------------------------------------- 
        // 2 configure resource paths
        //----------------------------------------------------- 
        let cf = new ConfigFile()
        cf.Load("resources.cfg", "\t:=", true)

        // Go through all sections & settings in the file
        let seci = cf.GetSectionIterator()

        // Normally we would use the foreach syntax, which enumerates the values, but in this case we need CurrentKey too;
        while seci.MoveNext() do
            for pair in seci.Current do
                ResourceGroupManager.Singleton.AddResourceLocation(pair.Value, pair.Key, seci.CurrentKey)

        //----------------------------------------------------- 
        // 3 Configures the application and creates the window
        //----------------------------------------------------- 
        root.RenderSystem <- root.GetAvailableRenderers() |> Seq.find (fun rs -> rs.Name = "Direct3D9 Rendering Subsystem")
        root.RenderSystem.SetConfigOption("Full Screen", "No")
        root.RenderSystem.SetConfigOption("Video Mode", "640 x 480 @ 32-bit colour")

        root.Initialise(false) |> ignore
        let misc = new NameValuePairList()
        misc.["externalWindowHandle"] <- hWnd.ToString()
        let window = root.CreateRenderWindow("Simple Mogre Form Window", 0u, 0u, false, misc.ReadOnlyInstance)
        ResourceGroupManager.Singleton.InitialiseAllResourceGroups()

        //----------------------------------------------------- 
        // 4 Create the SceneManager
        // 
        //  ST_GENERIC = octree
        //  ST_EXTERIOR_CLOSE = simple terrain
        //  ST_EXTERIOR_FAR = nature terrain (depreciated)
        //  ST_EXTERIOR_REAL_FAR = paging landscape
        //  ST_INTERIOR = Quake3 BSP
        //----------------------------------------------------- 
        let sceneMgr = root.CreateSceneManager(SceneType.ST_GENERIC, "SceneMgr")
        sceneMgr.AmbientLight <- new ColourValue(0.5f, 0.5f, 0.5f)

        //----------------------------------------------------- 
        // 5 Create the camera 
        //----------------------------------------------------- 
        let camera = sceneMgr.CreateCamera("SimpleCamera")
        camera.Position <- new Vector3(0.0f, 0.0f, 100.0f)
        // Look back along -Z
        camera.LookAt(new Vector3(0.0f, 0.0f, -300.0f))
        camera.NearClipDistance <- 5.0f

        let viewport = window.AddViewport(camera)
        viewport.BackgroundColour <- new ColourValue(0.0f, 0.0f, 0.0f, 1.0f)

        let ent = sceneMgr.CreateEntity("ogre", "ogrehead.mesh")
        let node = sceneMgr.RootSceneNode.CreateChildSceneNode("ogreNode")
        node.AttachObject(ent)

    member this.Paint() =
        root.RenderOneFrame() |> ignore

    member this.Dispose() =
        if root <> null then
            root.Dispose()

type MogreForm() as this =
    inherit Form()

    let mogrePanel = new System.Windows.Forms.Panel()

    // Between Suspend and Resume Layout is normal form Designer Code
    do  base.SuspendLayout()

        mogrePanel.Location <- new System.Drawing.Point(0, 0)
        mogrePanel.Name <- "mogrePanel"
        mogrePanel.Size <- new System.Drawing.Size(483, 375)
        mogrePanel.TabIndex <- 0

        base.AutoScaleDimensions <- new System.Drawing.SizeF(6.0f, 13.0f)
        base.AutoScaleMode <- System.Windows.Forms.AutoScaleMode.Font
        base.ClientSize <- new System.Drawing.Size(483, 375)
        base.Controls.Add(mogrePanel)
        base.Name <- "MogreForm"
        base.Text <- "Simple F# Mogre Form";

        base.ResumeLayout(false)

        let mogreWin = new OgreWindow(Point(100, 30), mogrePanel.Handle)
        this.Disposed.Add(fun _ -> mogreWin.Dispose())
        this.Paint.Add(fun _ -> mogreWin.Paint())

let main() =
    Application.EnableVisualStyles()
    Application.SetCompatibleTextRenderingDefault(false)
    Application.Run(new MogreForm())

[]
do main()

I'm impressed by how easy it is to use Models in XNA and because of this I'm demoting my render engine to line drawing only. Here is how I went about getting Models into my game.

1. First you will need software to create models and Autodesk has a free version of just that. Autodesk Softimage Mod Tool 7.5
2. Watch this video so you can create and export your 3D models correctly. The video series and blog post can be found here.
   
3. Third you can follow the Microsoft tutorials to get your models in game Microsoft Tutorial on displaying a 3D Model or you can continue the blog from the previous step.
   
4. Finally you will need some video tutorials on how to use Autodesk to create more complex models. XSI Video Tutorials

I added the Farseer Physics Engine to my game along with XNA sound effects. I'm amazed by how easy it was to use this physics engine. Collisions are handled by Delegates which you create in F# by passing a function to the delegate constructor.

ball.Geometry.OnCollision <- 
    Geom.CollisionEventHandler(
        fun geom1 geom2 contactList -> true)

My current plan is to add different shapes to the blocks, different masses, and maybe events such as an explosion.

For my next game Breakout, I need to detect collisions for a moving object. I choose line segments to represent object borders and motion. Calculating line segment intersections is a simple and fast algorithm and there are more advanced scan line algorithms to speed it up if needed. In order to use it, I take the ball's position and old position as the line segment for the ball.

The hard part of any collision algorithm is of course dealing with the collision. Detection is always easy because it's been done before. I'm doing collision with a simple reflection of the velocity off of the line segment it's intersecting. This works great until you collide close to another line segment and you happen to reflect to the other side of it. To fix this, I made the intersection and reflection algorithm recursive. This works great except for possible race conditions. Also, you no longer have a constant speed for your ball. A quick fix for the race condition is to check to make sure you can't intersect with the same line segment twice in a row. Having the ball move a little faster is acceptable.

Here's a burn test where I had set the ball to a very high speed to see if it could escape it's enclosure or enter one of the other objects. In order to make any errors apparent, I added a line trail of a random colors behind the ball. This ends up filling in all of the movable area.

I must say it's pretty cool to see the ball travel to every little nook and cranny of the board. This must be how particle chaos works. Like a fragrance filling the room.

I learned a few things on this project. One is that arrays are not the end all of data structures. My first instinct from my C++ background was to make a 2D array for the tetris game board. After wasting an hour or two I realized that it was over complicated and that a Set would work really well.

Basically each piece in the game is a set of tuple points. The game board boarder is a set of tuple points and the already fallen pieces is a set of pieces. I had to keep the concept of a piece in order to keep the color associated with each tuple point. This setup made collision detection simple. It was just a matter of Seq.union_all and Set.intersect

I'm pretty amazed by the relatively few lines of code it took me to recreate the game. The main game logic is incredibly small. Most of the code is spent setting up the system and handling user input/graphics.

Project Time: 13 hours
Project - Source Code

The game is played with the DPad and A/B buttons.

So I decided while working on my platformer that I need to reduce the number of jobs I'm undertaking while I program. In order to do that I'm dropping creative director and am instead recreating classic titles. I'm still project manager since I need to manage my time and my development goal has to be playability if I'm ever going to get anything playable.