// Changes between two textures assigned to a material
// When pressed space
var mat : Material;
private var flagTex : boolean = true;
function Update() {
    if (Input.GetKeyDown(KeyCode.Space)) {
        if(flagTex) {
            flagTex = false;
        } else {
            flagTex = true;
        }
    }
}

function OnPostRender() {
    if (!mat) {
        Debug.LogError("Please Assign a material on the inspector");
        return;
    }
    GL.PushMatrix();
    mat.SetPass(1);
    GL.LoadOrtho();
    GL.Begin(GL.QUADS);
    if (flagTex) {
        GL.MultiTexCoord2(0,0,0); // main texture
    } else {
        GL.MultiTexCoord2(1,0,0); // second texture
    }
    GL.Vertex3(0.25,0.25,0);
    if (flagTex) {
        GL.MultiTexCoord2(0,0,1);
    } else {
        GL.MultiTexCoord2(1,0,1);
    }
    GL.Vertex3(0.25,0.75,0);
    if (flagTex) {
        GL.MultiTexCoord2(0,1,1);
    } else {
        GL.MultiTexCoord2(1,1,1);
    }
    GL.Vertex3(0.75,0.75,0);
    if (flagTex) {
        GL.MultiTexCoord2(0,1,0);
    } else {
        GL.MultiTexCoord2(1,1,0);
    }
    GL.Vertex3(0.75,0.25,0);
    GL.End();
    GL.PopMatrix();
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public Material mat;
    private bool flagTex = true;
    void Update() {
        if (Input.GetKeyDown(KeyCode.Space))
            if (flagTex)
                flagTex = false;
            else
                flagTex = true;
        
    }
    void OnPostRender() {
        if (!mat) {
            Debug.LogError("Please Assign a material on the inspector");
            return;
        }
        GL.PushMatrix();
        mat.SetPass(1);
        GL.LoadOrtho();
        GL.Begin(GL.QUADS);
        if (flagTex)
            GL.MultiTexCoord2(0, 0, 0);
        else
            GL.MultiTexCoord2(1, 0, 0);
        GL.Vertex3(0.25F, 0.25F, 0);
        if (flagTex)
            GL.MultiTexCoord2(0, 0, 1);
        else
            GL.MultiTexCoord2(1, 0, 1);
        GL.Vertex3(0.25F, 0.75F, 0);
        if (flagTex)
            GL.MultiTexCoord2(0, 1, 1);
        else
            GL.MultiTexCoord2(1, 1, 1);
        GL.Vertex3(0.75F, 0.75F, 0);
        if (flagTex)
            GL.MultiTexCoord2(0, 1, 0);
        else
            GL.MultiTexCoord2(1, 1, 0);
        GL.Vertex3(0.75F, 0.25F, 0);
        GL.End();
        GL.PopMatrix();
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public mat as Material

    private flagTex as bool = true

    def Update():
        if Input.GetKeyDown(KeyCode.Space):
            if flagTex:
                flagTex = false
            else:
                flagTex = true

    def OnPostRender():
        if not mat:
            Debug.LogError('Please Assign a material on the inspector')
            return
        GL.PushMatrix()
        mat.SetPass(1)
        GL.LoadOrtho()
        GL.Begin(GL.QUADS)
        if flagTex:
            GL.MultiTexCoord2(0, 0, 0)
        else:
            GL.MultiTexCoord2(1, 0, 0)
        GL.Vertex3(0.25F, 0.25F, 0)
        if flagTex:
            GL.MultiTexCoord2(0, 0, 1)
        else:
            GL.MultiTexCoord2(1, 0, 1)
        GL.Vertex3(0.25F, 0.75F, 0)
        if flagTex:
            GL.MultiTexCoord2(0, 1, 1)
        else:
            GL.MultiTexCoord2(1, 1, 1)
        GL.Vertex3(0.75F, 0.75F, 0)
        if flagTex:
            GL.MultiTexCoord2(0, 1, 0)
        else:
            GL.MultiTexCoord2(1, 1, 0)
        GL.Vertex3(0.75F, 0.25F, 0)
        GL.End()
        GL.PopMatrix()