Example 2-7: Marking Polygon Boundary Edges

An easy one this, especially since I now have learned how to create and pass suitable arrays to the gl*() functions.

Here's the code:

# Example 2-7 : Marking Polygon Boundary Edges

from pyglet.gl import *
from pyglet import window

# The OpenGL context is created only when you create a window. Any calls
# to OpenGL before a window is created will fail.
win = window.Window()
    
def display():
    # vertices undefined in example
    # adding a Z value of 1.0 (simply to remain in sync with the example, 
    # where glVertex3fv is called, 
    # i.e. 3 variables are required by the function
    
    v0 = [0.0, 0.0, 1.0]
    v1 = [100.0, 100.0, 1.0]
    v2 = [150.0, 50.0, 1.0]
    
    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE)
    glBegin(GL_POLYGON)
    glEdgeFlag(GL_TRUE)
    glVertex3fv((GLfloat * len(v0))(*v0))
    glEdgeFlag(GL_FALSE)
    glVertex2fv((GLfloat * len(v1))(*v1))
    glEdgeFlag(GL_TRUE)  
    glVertex2fv((GLfloat * len(v2))(*v2))
    glEnd()
    
def init():
    glClearColor (0.0, 0.0, 0.0, 0.0)
    glShadeModel (GL_FLAT)

while not win.has_exit:
    win.dispatch_events()
    win.clear()
    display()
    win.flip()

One thing to note perhaps is that instead of passing the values directly, we have used a pointer to an array this time.