So a sky box, having done the Hazy Mind tutorial and had a
play with Riemers tutorials I decided to create my own skybox. I like the way
both tutorials do there sky box's but I kind of like cube maps, it means I keep
6 textures in one place, have only one texture variable and so makes my life a
little easier when passing textures to my skybox. So my version of a skybox uses
a box mesh (the same one from Riemers tutorial) but instead of passing a texture
to each side of the box or having to pass multiple textures to the mesh I just
pass a single cube map. I then wrote a shader to render the cube map on the
skybox mesh.
In this example I also have a basic camera that is a static
class, this does not use the GameComponents at all as I want it to be used by
all drawable elements in my code, so this class is driven by the game loop
directly from in my game class.
So, the code...
SkyBox
Class
public class SkyBox : DrawableGameComponent
{
private Model skyboxMesh;
public Vector3 myPosition;
public Quaternion myRotation;
public Vector3 myScale;
public TextureCube environ;
Effect shader;
string
modelAsset;
string shaderAsset;
string textureAsset;
ContentManager content;
public SkyBox(Game game,string modelAsset,string shaderAsset,string textureAsset) : base(game)
{
content =
new ContentManager(game.Services);
this.modelAsset = modelAsset;
this.shaderAsset = shaderAsset;
this.textureAsset =
textureAsset;
myPosition = new Vector3(0,
0, 0);
myRotation = new
Quaternion(0, 0, 0, 1);
myScale = new Vector3(55, 55, 55);
}
protected override void
LoadGraphicsContent(bool loadAllContent)
{
if
(loadAllContent)
{
skyboxMesh =
content.Load<Model>(modelAsset);
shader =
content.Load<Effect>(shaderAsset);
environ =
content.Load<TextureCube>(textureAsset);
}
base.LoadGraphicsContent(loadAllContent);
}
public override void
Draw(GameTime gameTime)
{
Matrix World =
Matrix.CreateScale(myScale) *
Matrix.CreateFromQuaternion(myRotation) *
Matrix.CreateTranslation(Camera.myPosition);
shader.Parameters["World"].SetValue(World);
shader.Parameters["View"].SetValue(Camera.myView);
shader.Parameters["Projection"].SetValue(Camera.myProjection);
shader.Parameters["surfaceTexture"].SetValue(environ);
shader.Parameters["EyePosition"].SetValue(Camera.myPosition);
for (int pass = 0;
pass < shader.CurrentTechnique.Passes.Count; pass++)
{
for (int msh = 0;
msh < skyboxMesh.Meshes.Count; msh++)
{
ModelMesh mesh = skyboxMesh.Meshes[msh];
for (int prt =
0; prt < mesh.MeshParts.Count; prt++)
mesh.MeshParts[prt].Effect = shader;
mesh.Draw();
}
}
base.Draw(gameTime);
}
}
Camera Class
public sealed class
Camera
{
public static Vector3 myPosition;
public static
Vector3 myTarget;
public static Quaternion myRotation;
private static
Matrix myWorld;
public static Matrix myView;
public static
Matrix myProjection;
public static Viewport myViewport;
private Camera()
{ }
public static void
Initialize()
{
myTarget = new Vector3();
myPosition = new Vector3(0,
0, 0);
myRotation = new
Quaternion(0, 0, 0, 1);
}
public static
void Update()
{
myWorld = Matrix.Identity;
myView =
Matrix.Invert(Matrix.CreateFromQuaternion(myRotation) *
Matrix.CreateTranslation(myPosition));
float aspectRatio = myViewport.Width /
myViewport.Height;
myProjection =
Matrix.CreatePerspectiveFieldOfView(1,
aspectRatio, myViewport.MinDepth, myViewport.MaxDepth);
myProjection = Matrix.CreatePerspectiveFieldOfView(MathHelper.Pi / 3.0f, (float)myViewport.Width / (float)myViewport.Height, myViewport.MinDepth,
myViewport.MaxDepth);
}
public static
void Rotate(Vector3 axis, float angle)
{
axis =
Vector3.Transform(axis, Matrix.CreateFromQuaternion(myRotation));
myRotation = Quaternion.Normalize(Quaternion.CreateFromAxisAngle(axis, angle) *
myRotation);
Update();
}
public static
void Translate(Vector3 distance)
{
myPosition += Vector3.Transform(distance,
Matrix.CreateFromQuaternion(myRotation));
Update();
}
public static void
Revolve(Vector3 target, Vector3 axis, float
angle)
{
Rotate(axis, angle);
Vector3
revolveAxis = Vector3.Transform(axis, Matrix.CreateFromQuaternion(myRotation));
Quaternion rotate = Quaternion.CreateFromAxisAngle(revolveAxis,
angle);
myPosition = Vector3.Transform(target - myPosition,
Matrix.CreateFromQuaternion(rotate));
Update();
}
}
SkyBox Shader
//////////////////////////////////////////////////////////////
//
//
// Writen by
C.Humphrey //
// 26/07/2007
//
//
//
//
//
// Shader used to render a cube map to an inverted box
//
// mesh.
//
//
//
//////////////////////////////////////////////////////////////
Texture surfaceTexture;
samplerCUBE TextureSampler =
sampler_state
{
texture = <surfaceTexture> ;
magfilter =
LINEAR;
minfilter = LINEAR;
mipfilter = LINEAR;
AddressU =
Mirror;
AddressV = Mirror;
};
float4x4 World : World;
float4x4 View : View;
float4x4 Projection : Projection;
float3
EyePosition : CameraPosition;
struct
VS_INPUT
{
float4 Position : POSITION0;
float3 Normal :
NORMAL0;
};
struct VS_OUTPUT
{
float4 Position : POSITION0;
float3 ViewDirection :
TEXCOORD2;
};
float4 CubeMapLookup(float3 CubeTexcoord)
{
return
texCUBE(TextureSampler, CubeTexcoord);
}
VS_OUTPUT
Transform(VS_INPUT Input)
{
float4x4 WorldViewProjection =
mul(mul(World, View), Projection);
float3 ObjectPosition =
mul(Input.Position, World);
VS_OUTPUT Output;
Output.Position = mul(Input.Position, WorldViewProjection);
Output.ViewDirection = EyePosition - ObjectPosition;
return Output;
}
struct PS_INPUT
{
float3
ViewDirection : TEXCOORD2;
};
float4 BasicShader(PS_INPUT Input) :
COLOR0
{
float3 ViewDirection = normalize(Input.ViewDirection);
return
CubeMapLookup(-ViewDirection);
}
technique BasicShader
{
pass P0
{
VertexShader = compile vs_2_0 Transform();
PixelShader = compile ps_2_0 BasicShader();
}
}
So the sky box is instantiated like this in the Game1
constructor:
SkyBox skyBox = new SkyBox(this,"Content/Models/skybox", "Content/Shaders/skybox", "Content/Textures/cubeMap");
this.Components.Add(skyBox);
The
configuration of the camera is a little more detaild. First of all, I want the
user to resize the viewport, so I need to wire an event to manage this and
update the cameras viewport properties, also, if the user has multiple screens
and they drag the game from one window to the next, the camera viewport has to
be reset again so this even also needs to be wired. So first off I write my
methods to be called by the events.
/// <summary>
/// Should the user move the game screen over to another
monitor.
/// </summary>
/// <param
name="sender"></param>
/// <param name="e"></param>
void DeviceChanged(object sender, EventArgs e)
{
Camera.myViewport = graphics.GraphicsDevice.Viewport;
Camera.myViewport.MinDepth = 1f;
Camera.myViewport.MaxDepth = 1000f;
}
/// <summary>
/// Should the game window screen
size change.
/// </summary>
/// <param
name="sender"></param>
/// <param name="e"></param>
public void Resize(object sender, EventArgs e)
{
Camera.myViewport.Width = Window.ClientBounds.Width;
Camera.myViewport.Height = Window.ClientBounds.Height;
}
I now wire these events up in the Game1 constructor.
Window.ClientSizeChanged += new
EventHandler(Resize);
Window.ScreenDeviceNameChanged += new
EventHandler(DeviceChanged);
Now I have those bases covered
I need to initialize my camera, this is done in the Initialize method of the
Game1 class.
Camera.Initialize();
Camera.myViewport =
graphics.GraphicsDevice.Viewport;
Camera.myViewport.MinDepth =
1f;
Camera.myViewport.MaxDepth = 1000f;
Now all I have to do
is update my camera, and yes, you guessed it, this is done in the Update method
of the Game2 class.
Camera.Update();
ControlsMouse
rotates camera.
Esc to exit.
Again, any comments, issues, suggestions
or fixes, please comment here.
OOPS! I forgot to
add the following method to the SkyBox class, basicly without it if you move the
game window to another screen your app will crash as you will get memory
violations. Sorry. I have not updated the zip so you will have to do this
manualy, source from now on will include this method if needed.
protected override void
UnloadGraphicsContent(bool unloadAllContent)
{
content.Unload();
base.UnloadGraphicsContent(unloadAllContent);
}
GenericExampleSkyBox.zip
Posted
Mon, Oct 15 2007 9:53 PM
by
Nemo Krad