In OpenGL this matches glBegin; on other graphics APIs the same
functionality is emulated. Between GL.Begin and GL.End it is valid to
call GL.Vertex, GL.Color, GL.TexCoord and other immediate mode drawing
functions.
You should be careful about culling when drawing primitives yourself. The culling rules
may be different depending on which graphics API the game is running. In most cases the
safest way is to use Cull Off command in the shader.
Additional resources: GL.End.
using UnityEngine;
public class Example : MonoBehaviour
{
// Draws a Triangle, a Quad and a line
// with different colors
Material mat;
void OnPostRender()
{
if (!mat)
{
Debug.LogError("Please Assign a material on the inspector");
return;
}
GL.PushMatrix();
mat.SetPass(0);
GL.LoadOrtho();
GL.Begin(GL.TRIANGLES); // Triangle
GL.Color(new Color(1, 1, 1, 1));
GL.Vertex3(0.50f, 0.25f, 0);
GL.Vertex3(0.25f, 0.25f, 0);
GL.Vertex3(0.375f, 0.5f, 0);
GL.End();
GL.Begin(GL.QUADS); // Quad
GL.Color(new Color(0.5f, 0.5f, 0.5f, 1));
GL.Vertex3(0.5f, 0.5f, 0);
GL.Vertex3(0.5f, 0.75f, 0);
GL.Vertex3(0.75f, 0.75f, 0);
GL.Vertex3(0.75f, 0.5f, 0);
GL.End();
GL.Begin(GL.LINES); // Line
GL.Color(new Color(0, 0, 0, 1));
GL.Vertex3(0, 0, 0);
GL.Vertex3(0.75f, 0.75f, 0);
GL.End();
GL.PopMatrix();
}
}