Sets current texture coordinate (v.x,v.y,v.z) to the actual texture unit.

In OpenGL this matches glMultiTexCoord for the given texture unit if multi-texturing is available. On other graphics APIs the same functionality is emulated.

The Z component is used only when:
1. You access a cubemap (which you access with a vector coordinate, hence x,y & z).
2. You do "projective texturing", where the X & Y coordinates are divided by Z to get the final coordinate. This would be mostly useful for water reflections and similar things.

This function can only be called between GL.Begin and GL.End functions.

	// 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.MultiTexCoord(0,Vector3(0,0,0)); // main texture
		} else {
			GL.MultiTexCoord(1,Vector3(0,0,0)); // second texture
		}
		GL.Vertex3(0.25,0.25,0);
		if (flagTex) {
			GL.MultiTexCoord(0,Vector3(0,1,0));
		} else {
			GL.MultiTexCoord(1,Vector3(0,1,0));
		}
		GL.Vertex3(0.25,0.75,0);
		if (flagTex) {
			GL.MultiTexCoord(0,Vector3(1,1,0));
		} else {
			GL.MultiTexCoord(1,Vector3(1,1,0));
		}
		GL.Vertex3(0.75,0.75,0);
		if (flagTex) {
			GL.MultiTexCoord(0,Vector3(1,0,0));
		} else {
			GL.MultiTexCoord(1,Vector3(1,0,0));
		}
		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.MultiTexCoord(0, new Vector3(0, 0, 0));
        else
            GL.MultiTexCoord(1, new Vector3(0, 0, 0));
        GL.Vertex3(0.25F, 0.25F, 0);
        if (flagTex)
            GL.MultiTexCoord(0, new Vector3(0, 1, 0));
        else
            GL.MultiTexCoord(1, new Vector3(0, 1, 0));
        GL.Vertex3(0.25F, 0.75F, 0);
        if (flagTex)
            GL.MultiTexCoord(0, new Vector3(1, 1, 0));
        else
            GL.MultiTexCoord(1, new Vector3(1, 1, 0));
        GL.Vertex3(0.75F, 0.75F, 0);
        if (flagTex)
            GL.MultiTexCoord(0, new Vector3(1, 0, 0));
        else
            GL.MultiTexCoord(1, new Vector3(1, 0, 0));
        GL.Vertex3(0.75F, 0.25F, 0);
        GL.End();
        GL.PopMatrix();
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	public mat as Material

	private flagTex as bool = true

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

	def OnPostRender() as void:
		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.MultiTexCoord(0, Vector3(0, 0, 0))
		else:
			GL.MultiTexCoord(1, Vector3(0, 0, 0))
		GL.Vertex3(0.25F, 0.25F, 0)
		if flagTex:
			GL.MultiTexCoord(0, Vector3(0, 1, 0))
		else:
			GL.MultiTexCoord(1, Vector3(0, 1, 0))
		GL.Vertex3(0.25F, 0.75F, 0)
		if flagTex:
			GL.MultiTexCoord(0, Vector3(1, 1, 0))
		else:
			GL.MultiTexCoord(1, Vector3(1, 1, 0))
		GL.Vertex3(0.75F, 0.75F, 0)
		if flagTex:
			GL.MultiTexCoord(0, Vector3(1, 0, 0))
		else:
			GL.MultiTexCoord(1, Vector3(1, 0, 0))
		GL.Vertex3(0.75F, 0.25F, 0)
		GL.End()
		GL.PopMatrix()