# Matrix.LookAtLH(Vector3,Vector3,Vector3) Method (Microsoft.DirectX)

How Do I...?

Builds a left-handed look-at matrix.

Definition

Visual Basic Public Shared Function LookAtLH( _    ByVal cameraPosition As Vector3, _    ByVal cameraTarget As Vector3, _    ByVal cameraUpVector As Vector3 _) As Matrix public static Matrix LookAtLH(    Vector3 cameraPosition,    Vector3 cameraTarget,    Vector3 cameraUpVector); public: static Matrix LookAtLH(    Vector3 cameraPosition,    Vector3 cameraTarget,    Vector3 cameraUpVector); public static function LookAtLH(    cameraPosition : Vector3,    cameraTarget : Vector3,    cameraUpVector : Vector3) : Matrix;

Parameters

 cameraPosition Microsoft.DirectX.Vector3 A Vector3 structure that defines the camera point. This value is used in translation. cameraTarget Microsoft.DirectX.Vector3 A Vector3 structure that defines the camera look-at target. cameraUpVector Microsoft.DirectX.Vector3 A Vector3 structure that defines the up direction of the current world, usually [0, 1, 0].

Return Value

Microsoft.DirectX.Matrix
A Matrix structure that is a left-handed look-at matrix.

Remarks

This method uses the following formula to compute the returned matrix.

zaxis = normal(cameraTarget - cameraPosition)
xaxis = normal(cross(cameraUpVector, zaxis))
yaxis = cross(zaxis, xaxis)

xaxis.x           yaxis.x           zaxis.x          0
xaxis.y           yaxis.y           zaxis.y          0
xaxis.z           yaxis.z           zaxis.z          0
-dot(xaxis, cameraPosition)  -dot(yaxis, cameraPosition)  -dot(zaxis, cameraPosition)  1


How Do I...?

Set Up a View Matrix

This example demonstrates how to initialize the view transformation matrix, which transforms world coordinates into camera or view space.

In the following C# code example, the vector components of the Vector3 structure form the arguments for the LookAtLH method, which builds a left-handed (LH) look-at matrix. The View transformation matrix is set to be equal to this look-at matrix.

The three input vectors represent the following, respectively:

1. The eye point: [0, 3, -5].
2. The camera look-at target: the origin [0, 0, 0].
3. The current world's up-direction: usually [0, 1, 0].

[C#]

using Microsoft.DirectX.Direct3D;

Device device = null;  // Create rendering device.

// Set up the view matrix. A view matrix can be defined given an eye point,
//   a point to view, and a direction for which way is up. Here, you set
//   the eye five units back along the z-axis and up three units, view the
//   origin, and define "up" to be in the y-direction.

device.Transform.View = Microsoft.DirectX.Matrix.LookAtLH(
new Vector3(0.0f, 3.0f, -5.0f),
new Vector3(0.0f, 0.0f, 0.0f),
new Vector3(0.0f, 1.0f, 0.0f));