GL.LoadPixelMatrix

Description

Setup a matrix for pixel-correct rendering.

This sets up modelview and projection matrices so that X, Y coordinates map directly to pixels. The (0,0) is at the bottom left corner of current camera's viewport. The Z coordinate goes from -1 to +1.

This function overrides current camera's parameters, so most often you want to save and restore matrices using GL.PushMatrix and GL.PopMatrix.

using UnityEngine;

public class Example : MonoBehaviour
{
    // Draws a red triangle using pixels as coordinates to paint on.
    Material mat;

    void OnPostRender()
    {
        if (!mat)
        {
            Debug.LogError("Please Assign a material on the inspector");
            return;
        }
        GL.PushMatrix();
        mat.SetPass(0);
        GL.LoadPixelMatrix();
        GL.Color(Color.red);

        GL.Begin(GL.TRIANGLES);
        GL.Vertex3(0, 0, 0);
        GL.Vertex3(0, Screen.height / 2, 0);
        GL.Vertex3(Screen.width / 2, Screen.height / 2, 0);
        GL.End();

        GL.PopMatrix();
    }
}

Description

Setup a matrix for pixel-correct rendering.

This sets up modelview and projection matrices so that X, Y coordinates map directly to pixels. The (left,bottom is at the bottom left corner of current camera's viewport; and (top,right) is at the top right corner of current camera's viewport. The Z coordinate goes from -1 to +1.

This function overrides current camera's parameters, so most often you want to save and restore matrices using GL.PushMatrix and GL.PopMatrix.