# LoadOrtho()

> Helper function to set up an orthograhic projection.

## Definition

* **Type:** Method
* **Namespace:** [UnityEngine](/engine/6000.6/script-reference/unityengine.md)
* **Assembly:** UnityEngine.CoreModule

```csharp
public static void LoadOrtho()
```

### Remarks

Loads an orthographic projection into the projection matrix and loads an identity into the model and view matrices.

The resulting projection performs the following mappings:

**1.** x = 0..1 to x = -1..1 (left..right)

**2.** y = 0..1 to y = -1..1 (bottom..top)

**3.** z = 1..-100 to z = -1..1 (near..far)

This is equivalent to the following operations:

```csharp
using UnityEngine;

public class Example : MonoBehaviour
{
    void OnPostRender()
    {
        // ...

        GL.LoadOrtho();

        // is equivalent to:

        GL.LoadIdentity();
        var proj = Matrix4x4.Ortho(0, 1, 0, 1, -1, 100);
        GL.LoadProjectionMatrix(proj);

        // ...
    }
}
```

Changing the model, view or projection matrices overrides the current rendering matrices. It is good practice to save and restore these matrices using [GL.PushMatrix](/engine/6000.6/script-reference/unityengine/gl/pushmatrix.md) and [GL.PopMatrix](/engine/6000.6/script-reference/unityengine/gl/popmatrix.md).

```csharp
using UnityEngine;

public class Example : MonoBehaviour
{
    // Draws a triangle under an already drawn triangle
    Material mat;

    void OnPostRender()
    {
        if (!mat)
        {
            Debug.LogError("Please Assign a material on the inspector");
            return;
        }
        GL.PushMatrix();
        mat.SetPass(0);
        GL.LoadOrtho();
        GL.Color(Color.red);
        GL.Begin(GL.TRIANGLES);
        GL.Vertex3(0.25f, 0.1351f, 0);
        GL.Vertex3(0.25f, 0.3f, 0);
        GL.Vertex3(0.5f, 0.3f, 0);
        GL.End();

        GL.Color(Color.yellow);
        GL.Begin(GL.TRIANGLES);
        GL.Vertex3(0.5f, 0.25f, -1);
        GL.Vertex3(0.5f, 0.1351f, -1);
        GL.Vertex3(0.1f, 0.25f, -1);
        GL.End();

        GL.PopMatrix();
    }
}
```

Additional Resources: [GL.LoadProjectionMatrix](/engine/6000.6/script-reference/unityengine/gl/loadprojectionmatrix.md), [Matrix4x4.Ortho](/engine/6000.6/script-reference/unityengine/matrix4x4/ortho.md).