# How To: Make a First-Person Camera

XNA Game Studio 2.0
This example demonstrates how to create a first-person camera.

The example controls the camera by using the method shown in How To: Rotate and Move a Camera, with an additional offset for the camera to place it where the game avatar's head should be. The example assumes a model has been added to the project as described in How To: Render a Model.

# The Complete Sample

The code in this tutorial illustrates the technique described in the text. A complete code sample for this tutorial is available for you to download, including full source code and any additional supporting files required by the sample.

### To make a first-person camera

1. Precalculate the camera's offset from the avatar. The offset is used to place the camera roughly where the avatar's head is.

```Vector3 avatarHeadOffset = new Vector3(0, 10, 0);
```
2. Track the position and rotation of the avatar during gameplay.
3. Create a rotation Matrix using CreateRotationY and the avatar's current direction.

```Matrix rotationMatrix = Matrix.CreateRotationY(avatarYaw);
```
4. Transform a copy of the camera's head offset using the rotation Matrix and Vector3.Transform.

```// Transform the head offset so the camera is positioned properly relative to the avatar.
```
5. Calculate the current position of the camera. The position of the camera will be the position of the avatar plus the avatar's transformed head offset.

```// Calculate the camera's current position.
Vector3 cameraPosition = avatarPosition + headOffset;
```
6. Transform a copy of the camera's reference vector using the rotation Matrix and Vector3.Transform.

```// Create a vector pointing the direction the camera is facing.
Vector3 transformedReference = Vector3.Transform(cameraReference, rotationMatrix);
```
7. Calculate the position the camera is looking at. This "look-at" position will be the camera's position plus the camera's transformed reference vector.

```// Calculate the position the camera is looking at.
Vector3 cameraLookat = transformedReference + cameraPosition;
```
8. Create a new view Matrix. The new Matrix is created by passing the camera position and camera lookat to CreateLookAt. The view Matrix controls how world coordinate values are transformed to camera coordinates.

```view = Matrix.CreateLookAt(cameraPosition, cameraLookat, new Vector3(0.0f, 1.0f, 0.0f));
```
9. Create a new projection Matrix with CreatePerspectiveFieldOfView. The projection Matrix controls how camera coordinate values are transformed to screen coordinates.

```Viewport viewport = graphics.GraphicsDevice.Viewport;
float aspectRatio = (float)viewport.Width / (float)viewport.Height;

proj = Matrix.CreatePerspectiveFieldOfView(viewAngle, aspectRatio, nearClip, farClip);
```
10. Loop through each model in the world drawing it as described in How To: Render a Model using the projection matrix and view matrix created above. For the world matrix, use Matrix.CreateTranslation and the object's current position in the world.

```void DrawBoxes()
{
for (int z = 0; z < 9; z++)
{
for (int x = 0; x < 9; x++)
{
DrawModel(box, Matrix.CreateTranslation(x * 60, 0, z * 60), boxTexture);
}
}
}

/// <summary>
/// Draws the 3D specified model.
/// </summary>
/// <param name="model">The 3D model being drawn.</param>
/// <param name="world">Transformation matrix for world coords.</param>
/// <param name="texture">Texture used for the drawn 3D model.</param>
void DrawModel(Model model, Matrix world, Texture2D texture)
{
foreach (ModelMesh mesh in model.Meshes)
{
foreach (BasicEffect be in mesh.Effects)
{
be.Projection = proj;
be.View = view;
be.World = world;
be.Texture = texture;
be.TextureEnabled = true;
}
mesh.Draw();
}
}
```