Now, before anyone judges me for not wanting to learn a new API, consider this.  Allegro has a plethora of 2D methods, but the only vector methods I am able to find are 3D.  Fine you say, just zero the Z element and be done with it.

Well sure.  But would I rather use a non OOP implementation like this:

float x = <someXValue>;
float y = <someYValue>;
float z = 0.0f;
void normalize_vector_f(float *x, float *y, float *z);

Or would I rather take an OOP approach:

Vector2D vec( <someXValue>, <someYValue> );
vec.Normalize();

Call me crazy, but I prefer the later.  As such, I’m going to go ahead and post my Vector2D class here, as well as the Rectangle class I am using.  Normally I would cite sources I used for help in writing these classes.   However, in the case of the Vector2D class most of the methods used are fairly standard and there is nothing really out of the ordinary.

As for the Rectangle class, there are some cool static methods I added that Microsoft released in their RectangleExtensions class (released under the MSPL).  I ported these methods over from C# to C++,and they seem to work correctly, however I haven’t tested them thoroughly and they may have a bug or two.

Anyway, enough ranting.  Here’s the code.

Vector2D.h

#ifndef _VECTOR2D_H
#define _VECTOR2D_H
#pragma once

#include <math.h>

class Vector2D
{

public:
	Vector2D(float x = 0, float y = 0);
	~Vector2D() {};

	void Rotate( const float angle );
	float Magnitude() const;
	float Normalize();
	float DotProduct( const Vector2D& v2 ) const;
	float CrossProduct( const Vector2D& v2 ) const;

	static Vector2D Zero();
	static float Distance( const Vector2D& v1, const Vector2D& v2);

	Vector2D& operator= ( const Vector2D& v2 );

	Vector2D& operator+= ( const Vector2D& v2 );
	Vector2D& operator-= ( const Vector2D& v2 );
	Vector2D& operator*= ( const float scalar);
	Vector2D& operator/= ( const float scalar);

	const Vector2D operator+( const Vector2D &v2 ) const;
	const Vector2D operator-( const Vector2D &v2 ) const;
	const Vector2D operator*( const float scalar ) const;
	const Vector2D operator/( const float scalar ) const;

	bool operator== ( const Vector2D& v2 ) const;
	bool operator!= ( const Vector2D& v2 ) const;

public:
	float x, y;
};
#endif

Vector2D.cpp

#include "Vector2D.h"

//-----------------------------------------------------------------------------
// Purpose:	Constructor
//-----------------------------------------------------------------------------
Vector2D::Vector2D( float x, float y )
{
	this->x = x;
	this->y = y;
}

//-----------------------------------------------------------------------------
// Purpose:	Rotate a vector
//-----------------------------------------------------------------------------
void Vector2D::Rotate( const float angle )
{
	float xt = (x * cosf(angle)) - (y * sinf(angle));
	float yt = (y * cosf(angle)) + (x * sinf(angle));
	x = xt;
	y = yt;
}

//-----------------------------------------------------------------------------
// Purpose:	Get vector magnitude
//-----------------------------------------------------------------------------
float Vector2D::Magnitude() const
{
	return sqrtf(x * x + y * y);
}

//-----------------------------------------------------------------------------
// Purpose:	Convert vector to a unit vector and return previous magnitude
//-----------------------------------------------------------------------------
float Vector2D::Normalize()
{
	float mag = Magnitude();

	if(mag != 0.0)
	{
		x /= mag;
		y /= mag;
	}

	return mag;
}

//-----------------------------------------------------------------------------
// Purpose:	Dot Product
//-----------------------------------------------------------------------------
float Vector2D::DotProduct( const Vector2D &v2 ) const
{
	return (x * v2.x) + (y * v2.y);
}

//-----------------------------------------------------------------------------
// Purpose:	Cross Product
//-----------------------------------------------------------------------------
float Vector2D::CrossProduct( const Vector2D &v2 ) const
{
	return (x * v2.y) - (y * v2.x);
}

//-----------------------------------------------------------------------------
// Purpose:	Return an empty vector
//-----------------------------------------------------------------------------
Vector2D Vector2D::Zero()
{
	return Vector2D(0, 0);
}

//-----------------------------------------------------------------------------
// Purpose:	Get distance between two vectors
//-----------------------------------------------------------------------------
float Vector2D::Distance( const Vector2D& v1, const Vector2D& v2)
{
	return sqrtf( pow((v2.x - v1.x), 2 ) + pow((v2.y - v1.y), 2) );
}

Vector2D& Vector2D::operator= ( const Vector2D& v2 )
{
	if (this == &v2)
		return *this;

	x = v2.x;
	y = v2.y;

	return *this;
}

Vector2D& Vector2D::operator+= ( const Vector2D& v2 )
{
	x += v2.x;
	y += v2.y;

	return *this;
}

Vector2D& Vector2D::operator-= ( const Vector2D& v2 )
{
	x -= v2.x;
	y -= v2.y;

	return *this;
}

Vector2D& Vector2D::operator*= ( const float scalar )
{
	x *= scalar;
	y *= scalar;

	return *this;
}

Vector2D& Vector2D::operator/= ( const float scalar )
{
	x /= scalar;
	y /= scalar;

	return *this;
}

const Vector2D Vector2D::operator+( const Vector2D &v2 ) const
{
	return Vector2D(*this) += v2;
}

const Vector2D Vector2D::operator-( const Vector2D &v2 ) const
{
	return Vector2D(*this) -= v2;
}

const Vector2D Vector2D::operator*( const float scalar ) const
{
	return Vector2D(*this) *= scalar;
}

const Vector2D Vector2D::operator/( const float scalar ) const
{
	return Vector2D(*this) /= scalar;
}

bool Vector2D::operator== ( const Vector2D& v2 ) const
{
	return ((x == v2.x) && (y == v2.y));
}

bool Vector2D::operator!= ( const Vector2D& v2 ) const
{
	return !((x == v2.x) && (y == v2.y));
}

Rectangle.h

#ifndef _RECTANGLE_H
#define _RECTANGLE_H
#pragma once

#include "Vector2D.h"

class Rectangle
{
public:
	Rectangle( int x = 0, int y = 0, int w = 0, int h = 0 );
	~Rectangle( void ) {};

	inline int Left( void ) const { return x; }
	inline int Right( void ) const { return x + w; }
	inline int Top( void ) const { return y; }
	inline int Bottom( void ) const { return y + h; }

	bool Contains( Vector2D& vVec ) const;
	bool Contains( int x, int y ) const;

	static Rectangle Empty();

	// Static methods below are derived from the RectangleExtensions class
	// written in C#, released under the MSPL
	static Vector2D GetIntersectionDepth( const Rectangle& rectA, const Rectangle& rectB );
	static Vector2D GetBottomCenter( const Rectangle& rect );
	static Vector2D GetCenter( const Rectangle& rect );
	static float GetDistance( const Rectangle& rectA, const Rectangle& rectB);
	static Vector2D GetDirection( const Rectangle& rectA, const Rectangle& rectB);

	Rectangle& operator= ( const Rectangle& r2 );

	bool operator== ( const Rectangle& r2 ) const;
	bool operator!= ( const Rectangle& r2 ) const;

public:
	int x, y, w, h;
};

#endif

Rectangle.cpp

#include "Rectangle.h"
#include <stdlib.h>

//-----------------------------------------------------------------------------
// Purpose:	Constructor
//-----------------------------------------------------------------------------
Rectangle::Rectangle( int x, int y, int w, int h )
{
	this->x = x;
	this->y = y;
	this->w = w;
	this->h = h;
}

//-----------------------------------------------------------------------------
// Purpose:	Check if rectangle contains a 2D vector
//-----------------------------------------------------------------------------
bool Rectangle::Contains( Vector2D& vVec ) const
{
	if ( ( vVec.x >= x )&&
		 ( vVec.x <= x + w ) &&
		 ( vVec.y >= y ) &&
		 ( vVec.x <= y + h ) )
	{
		return true;
	}
	else
		return false;
}

//-----------------------------------------------------------------------------
// Purpose:	Check if rectangle contains a set of coords
//-----------------------------------------------------------------------------
bool Rectangle::Contains( int x, int y ) const
{
	if ( ( x >= this->x )&&
		( x <= this->x + this->w ) &&
		( y >= this->y ) &&
		( x <= this->y + this->h ) )
	{
		return true;
	}
	else
		return false;
}

//-----------------------------------------------------------------------------
// Purpose:	Return an empty rectangle
//-----------------------------------------------------------------------------
Rectangle Rectangle::Empty()
{
	return Rectangle();
}

//-----------------------------------------------------------------------------
// Purpose:	Get intersection depth between two rectangles
//-----------------------------------------------------------------------------
Vector2D Rectangle::GetIntersectionDepth( const Rectangle& rectA, const Rectangle& rectB )
{
	// Calculate half sizes.
	float halfWidthA = rectA.w / 2.0f;
	float halfHeightA = rectA.h / 2.0f;
	float halfWidthB = rectB.w / 2.0f;
	float halfHeightB = rectB.h / 2.0f;

	// Calculate centers.
	Vector2D centerA(rectA.x + halfWidthA, rectA.y + halfHeightA);
	Vector2D centerB(rectB.x + halfWidthB, rectB.y + halfHeightB);

	// Calculate current and minimum-non-intersecting distances between centers.
	float distanceX = centerA.x - centerB.x;
	float distanceY = centerA.y - centerB.y;
	float minDistanceX = halfWidthA + halfWidthB;
	float minDistanceY = halfHeightA + halfHeightB;

	// If we are not intersecting at all, return (0, 0).
	if ( abs(distanceX) >= minDistanceX || abs(distanceY) >= minDistanceY )
		return Vector2D::Zero();

	// Calculate and return intersection depths.
	float depthX = distanceX > 0 ? minDistanceX - distanceX : -minDistanceX - distanceX;
	float depthY = distanceY > 0 ? minDistanceY - distanceY : -minDistanceY - distanceY;
	return Vector2D(depthX, depthY);
}

//-----------------------------------------------------------------------------
// Purpose:	Gets the position of the center of the bottom edge of the rectangle.
//-----------------------------------------------------------------------------
Vector2D Rectangle::GetBottomCenter(const Rectangle& rect)
{
	return Vector2D( (float)(rect.x + rect.w / 2.0f), (float)(rect.y + rect.h) );
}

//-----------------------------------------------------------------------------
// Purpose:	Gets the position of the center point of a rectangle
//-----------------------------------------------------------------------------
Vector2D Rectangle::GetCenter(const Rectangle& rect)
{
	return Vector2D( (float)(rect.x + rect.w / 2.0f), (float)(rect.y + rect.h / 2.0f) );
}

//-----------------------------------------------------------------------------
// Purpose:	Gets the floating point distance between the center point
//			of one rectangle and the center point of another.
//-----------------------------------------------------------------------------
float Rectangle::GetDistance( const Rectangle& rectA, const Rectangle& rectB )
{
	return Vector2D::Distance(GetCenter(rectA), GetCenter(rectB));
}

//-----------------------------------------------------------------------------
// Purpose:	Gets the unit vector from one rectangle to another
//-----------------------------------------------------------------------------
Vector2D Rectangle::GetDirection( const Rectangle& rectA, const Rectangle& rectB )
{
	Vector2D direction = GetCenter(rectA) - GetCenter(rectB);
	direction.Normalize();
	return direction;
}

Rectangle& Rectangle::operator= ( const Rectangle& r2 )
{
	if (this == &r2)
		return *this;

	x = r2.x;
	y = r2.y;
	w = r2.w;
	h = r2.h;

	return *this;
}

bool Rectangle::operator== ( const Rectangle& r2 ) const
{
	return ((w == r2.w) && (h == r2.h));
}

bool Rectangle::operator!= ( const Rectangle& r2 ) const
{
	return !((w == r2.w) && (h == r2.h));
}

It’s been some time since my last progress update, and I have sort of fallen out of the groove.  As such, this is going to be a short post to sort of get back into the swing of things.

I spent a good while last night working out a good solution to adding rotating gear platforms into the Boilerworks.  The initial idea was simple.  I was going to simply convert the gear texture into a set of vertices and load them up as a collision volume.  However, I realized this solution was not going to be viable as I have been using SAT collision, and a single gear polygon would have been a concave polygon (not supported by SAT implementation).  I decided to try Distance Grid collision instead of SAT, but the difference was noticeable and caused some big headaches.

It doesn’t look like the good folks at Farseer will be implementing concave polygon decomposition until Farseer 3.0 is released, so I had to take an alternate route.

The end result was simply generating multiple convex geometries programmatically that matched mt gear texture.  This ended up working perfectly, and as such we now have some really nice gear platforms ready to be added to levels.  A screenshot of the testbed is below.

Hopefully I’ll start updating this a bit more often as development continues.

The solution: a very simple plugin architecture.  By very simple, I mean that the actual Map classes would not be changed at all, in fact the XML map that the editor exported would not be changed in the slightest.  The plugin would not so much be given access to the Map in any way, but more so it would be given a place to run.  Essentially (at this point anyway) the plugin would be aesthetic.  It would allow level designers to use additional functionality within the level editor, which would already be running on the system.

But enough about that, the reason for this post is that I wanted to share a bit of code that let this happen.  After doing some research, I came across an old post by Shawn Walcheske called “Implementing a Plug-In Architecture in C#” (located here: http://www.ddj.com/cpp/184403942).  My implementation is, basically, identical, however the source download on that page is down, and he doesn’t really explain the System.Activator class which leaves the reader hanging. Update from a reader. Apparently the source is still available here: ftp://ftp.cuj.com/sourcecode/cuj/2003/cujjan2003.zip. Thanks!

So with that, I thought I’d show how I went about doing things, and basically explain the few loose ends that Shawn leaves out.  I think it goes without saying that if you really want to understand this entire concept, read his article as well.

The first thing we need to do is create a simple interface for our plugin.  This interface needs to be in it’s own assembly, for example I created ParadigmCommon.dll for plugins to reference in order to have access to this interface.  As the plugin system I am developing is very simple, the interface only provides an ActivatePlugin() method, as all we want to do is be able to launch new plugins from the main editor.

    public interface IParadigmPlugin
    {
        /// <summary>
        /// Activates the plugin, showing it's main form
        /// </summary>
        void ActivatePlugin();
    }

Next we need to define some custom attributes.  These attributes will hold some metadata for our class, this way our main application can reference that data.  We are, for this example, going to create a custom DisplayName attribute, and a custom Description attribute.  They are fairly self explanatory.

    /// <summary>
    /// This class defines the custom attribute for plugin display names
    /// </summary>
    [AttributeUsage(AttributeTargets.Class)]
    public class ParadigmPluginDisplayNameAttribute : System.Attribute
    {
        private string displayName;
 
        public ParadigmPluginDisplayNameAttribute(string displayName)
            : base()
        {
            this.displayName = displayName;
        }
 
        public override string ToString()
        {
            return displayName;
        }
    }

    /// <summary>
    /// This class defines the custom attribute for plugin descriptions
    /// </summary>
    [AttributeUsage(AttributeTargets.Class)]
    public class ParadigmPluginDescriptionAttribute : System.Attribute
    {
        private string description;
 
        public ParadigmPluginDescriptionAttribute(string description)
            : base()
        {
            this.description = description;
        }
 
        public override string ToString()
        {
            return description;
        }
    }

Here we have an actual plugin.  As you can see, we need to use the ParadigmCommon namespace, as well as reference the DLL from the project.  The plugin itself merely implements the IParadigmPlugin interface and as such implements the ActivatePlugin() method, which only serves to open a new form for the plugin.  Simple enough.  Similar in implementation to the way Program.cs would launch the main form in a Windows application.  As you can see, we are also using our custom attributes.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms; // referencing System.Windows.Forms is obviously needed for form usage, make sure to reference it in the project as well
using ParadigmCommon; // you must reference the ParadigmCommon namespace to access the needed attributes and interface
 
namespace TestPlugin
{
    /// <summary>
    /// This is an example of a paradigm plugin
    /// </summary>
    [ParadigmPluginDisplayName("Test Plugin")] // you must provice a display name
    [ParadigmPluginDescription("Test Plugin")] // as well as a description
    public class TestPlugin : IParadigmPlugin  // Your main class must implement the IParadigmPlugin interface
    {
        public void ActivatePlugin() // by implementing the interface, you must implement an ActivatePlugin method
        {
            TestPluginMainForm mainForm = new TestPluginMainForm();
            mainForm.Show();
            mainForm.Activate();
        }
    }
}

In our host applciation, we need to define a few things.  First, we need a wrapper class. This class will hold a reference to an object implementing our IParagidmPlugin interface (ie: any plugin we create), as well as the metadata for the plugin (in our case, name and description). In this case we also implement an Activate() method that will call the actual plugin’s ActivatePlugin() method.

    /// <summary>
    /// This class wraps our plugins
    /// </summary>
    public class ParadigmPlugin
    {
        #region Fields
        private IParadigmPlugin plugin;
        private string name;
        private string description;
        #endregion
 
        #region Attributees
        public string Name
        {
            get { return name; }
        }
 
        public string Description
        {
            get { return description; }
        }
        #endregion
 
        /// <summary>
        /// Constructs a plugin wrapper
        /// </summary>
        public ParadigmPlugin(IParadigmPlugin plugin, string name, string description)
        {
            this.plugin = plugin;
            this.name = name;
            this.description = description;
        }
 
        /// <summary>
        /// Activate Plugin
        /// </summary>
        public void Activate()
        {
            plugin.ActivatePlugin();
        }

We also need to define a quick custom exception, which we will use later on. There is really no implementation here in the example, but you can handle the exception however you wish.

    class PluginNotValidException : ApplicationException
    {
        public PluginNotValidException(Type type, string param1)
        {
        }
    }

First, we need to define a list to contain all of the plugins we load at runtime.  Next, we need a LoadPlugins() method.  This method uses reflection to handle plugin loading.  Essentially, it steps through our plugin directory looking for any file that matches the *.dll file name mask.  When it finds a DLL, it attempts to load the assembly.  If it fails, it will throw an exception and alert the user.

If it succeeds in loading the assembly, and looks for our IParadigmInterface.  If it finds it, it then gets our custom attributes.

Next, the System.Activator class comes into play.  This wasn’t mentioned in Shawn’s article as I said before.  Basically, we are going to create an object of a specific type, which in this case our type is going to be pulled from the loaded assembly, this way we create the correct type of object.

Next, we create an instance of our wrapper class.  Upon constructing, we are going to make sure to cast the object returned by System.Activator as IParadigmPlugin.  We will then add it to our list of loaded plugins.  Thats it.

The last part of this function is optional, but pretty cool and may be helpful.  Basically, we want our loaded plugins to show up dynamically on a menu strip.  So, we will iterate through our list of loaded plugins, and for each one we will add a new item to a toolstrip menu dropdown list.  We will set the name and text to the plugin display name, and the tool tip to the plugin description (see, we used the metadata for something afterall).  Then, we will set the new items Click event to be a delegate referencing the plugin’s Activate() method.  Simple right?  When this method executes, our tool strip will be dynamically populated by the plugins, and clicking them will launch them.

private List<ParadigmPlugin> loadedPlugins = new List<ParadigmPlugin>();

        private void LoadPlugins()
        {
            // search plugin directory for dlls
            string[] files = Directory.GetFiles("Plugins", "*.dll");
 
            // check each file in plugin direction
            foreach (string file in files)
            {
                try
                {
                    // load the assembly and get types
                    Assembly assembly = Assembly.LoadFrom(file);
                    System.Type[] types = assembly.GetTypes();
 
                    // look for our interface in the assembly
                    foreach (System.Type type in types)
                    {
                        // if we found our interface, verify attributes
                        if (type.GetInterface("IParadigmPlugin") != null)
                        {
 
                            if (type.GetCustomAttributes(typeof(ParadigmPluginDisplayNameAttribute), false).Length != 1)
                                throw new PluginNotValidException(type, "Plugin display name is not supported!");
 
                            if (type.GetCustomAttributes(typeof(ParadigmPluginDescriptionAttribute), false).Length != 1)
                                throw new PluginNotValidException(type, "Plugin description is not supported");
 
                            // get custom attributes from plugin
                            string name = type.GetCustomAttributes(typeof(ParadigmPluginDisplayNameAttribute), false)[0].ToString();
                            string description = type.GetCustomAttributes(typeof(ParadigmPluginDescriptionAttribute), false)[0].ToString();
 
                            // create the plugin using reflection
                            Object o = Activator.CreateInstance(type);
 
                            ParadigmPlugin plugin = new ParadigmPlugin(o as IParadigmPlugin, name, description);                                                               
 
                            loadedPlugins.Add(plugin);
                        }
                    }
                }
                catch (Exception e)
                {
                    MessageBox.Show(e.Message, "Plugin Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
            }
 
            // iterate through list and add them to our form control
            for (int i = 0; i < loadedPlugins.Count; i++)
            {
                ParadigmPlugin plugin = loadedPlugins[i];
 
                pluginsToolStripMenuItem.DropDownItems.Add(plugin.Name);
                pluginsToolStripMenuItem.DropDownItems[i].Click += delegate { plugin.Activate(); };
                pluginsToolStripMenuItem.DropDownItems[i].Text = plugin.Name;
                pluginsToolStripMenuItem.DropDownItems[i].ToolTipText = plugin.Description;
            }
        }

You could easily expose much more via the interface and make some complicated plugins, but that isn’t needed in this scenario.  However, I hope this helps to illuminate the basics of plugin architecture in C#.

As it stands now, rendering is working perfectly, along with collision, multiple layers supporting occlusion, collidable NPC’s, and NPC/Player occlusion based on world placement.

In the coming days / weeks I will be uploading some reports on progress, as well as some videos of development.

At that time a new entry will be made to my portfolio which will underline the scope of the game, as well as my actual involvement in the project.

Stay tuned.

As such, a few changes are planned.

1. Shadow mapping.  I have a few different ideas on to how create shadows with a decent degree of alpha transparency.  More than likely I will go with a separate B&W image that stores that shadow textures and have the engine draw them as needed with alpha transparency.
2. Layers, layers, LAYERS.  Three layers, simply, is not enough.  As such, I’m going to transition from the current 3 layer system to an unlimited layer system.
3. Zooming.  RPG maps are going to be somewhat large.  I think zooming in and out of the editor will be a very helpful addition.
4. Advanced entity spawning system.  I’m on the fence with this one.  I may or may not implement this in the editor.  Part of me thinks creating an NPC editor would be smarter.  We’ll see how this pans out though.

That is all for now.

As it stands, the editor is pretty robust.  Currently it supports three tile layers, a rear, mid, and foreground layer.  The rear layer is self explanatory.  The mid layer renders over the rear layer to add details, and the foreground layer renders over NPCs, the player, particles, etc (as long as your engine supports it).  The foreground layer is currently tinted yellow so it can be distinguished.

Tiles can be drawn in as single tiles and regions.  You can also choose to fill an entire layer with a single tile if you so choose.

The editor supports multiple collision types such as impassible, platform, slopes, etc.  These are basically just flags that your engine needs to interpret correctly.

The editor also supports spawn points.  Any entity your engine supports can be dumped into a plain text file and the editor will parse it.  The spawn points can be added dynamically to the map.

It also supports a portal layer which allows for areas of the map to be flagged as a portal.  This allows for your engine to do a check against those regions and load a new map as needed.

We also support terrain effects which are regions of the map that will be processed with some sort of effect.  My demo shows this being used with a simple water shader I wrote.

You can set the background color of the map to any of the predefined .NET colors, as well as a custom color using the color wheel.  You can resize the map dynamically as well as specify the tile size to match your tile set.

The next iteration of this editor will support more layers, likely unlimited using just a list of layers.  In addition I plan to implement a sort of multilayer occlusion so that the foreground layer is more or less dynamic.  Different layers will occlude other layers, so on and so forth.  This is not really needed for a platformer, but will be pretty useful in RPG world building.

Videos:

(My apologies as the audio goes out of sync near the end of part 1 and into part 2, blame Camstudio.)

Basically, pretty sweet.

Here is a screenshot for the time being.

Level Editor Alpha

I hope to have a few enemies functional in the next few days, but this is dependent on time.