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.

	// Draws a red triangle using pixels as coordinates to paint on.
	var mat : Material;
	function 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();
	}

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    public 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();
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	public mat as Material

	def OnPostRender() as void:
		if not 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()

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.

	var mat : Material;
	function OnPostRender() {
		if (!mat) {
			Debug.LogError("Please Assign a material on the inspector");
			return;
		}
		GL.PushMatrix();
		mat.SetPass(0);
		GL.LoadPixelMatrix(10,20,10,20);
		GL.Color(Color.red);
		GL.Begin(GL.TRIANGLES);
		GL.Vertex3(10,10,0);
		GL.Vertex3(10,20,0);
		GL.Vertex3(20,20,0);
		GL.End();
		GL.PopMatrix();
	}

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    public Material mat;
    void OnPostRender() {
        if (!mat) {
            Debug.LogError("Please Assign a material on the inspector");
            return;
        }
        GL.PushMatrix();
        mat.SetPass(0);
        GL.LoadPixelMatrix(10, 20, 10, 20);
        GL.Color(Color.red);
        GL.Begin(GL.TRIANGLES);
        GL.Vertex3(10, 10, 0);
        GL.Vertex3(10, 20, 0);
        GL.Vertex3(20, 20, 0);
        GL.End();
        GL.PopMatrix();
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	public mat as Material

	def OnPostRender() as void:
		if not mat:
			Debug.LogError('Please Assign a material on the inspector')
			return
		GL.PushMatrix()
		mat.SetPass(0)
		GL.LoadPixelMatrix(10, 20, 10, 20)
		GL.Color(Color.red)
		GL.Begin(GL.TRIANGLES)
		GL.Vertex3(10, 10, 0)
		GL.Vertex3(10, 20, 0)
		GL.Vertex3(20, 20, 0)
		GL.End()
		GL.PopMatrix()