NeHe Translations: Creating Your First Polygon & Quad (NeHe 2)

#! /usr/bin/env python

Creating Your First Polygon & Quad (NeHe 2)

Introduces:

glBegin/glEnd
glVertex
glTranslate

This tutorial is based on the NeHe2 tutorial by Jeff Molofee and assumes that you are reading along with the tutorial, so that only changes from the tutorial are noted here.

The previous tutorial discussed this setup procedure at length.

from OpenGLContext import testingcontext BaseContext = testingcontext.getInteractive() from OpenGL.GL import * class TestContext( BaseContext ): """Rendering Context with custom viewpoint and render Note: will have slightly different results as OpenGLContext automatically enables lighting. """

The first customization is the initialPosition attribute. By default, the OpenGLContext contexts position your eye/camera at (0,0,10), which makes it easy to see most meter-sized geometry located at the origin. Since the NeHe tutorial manually repositions the geometry to be in a good viewing position under the assumption that the eye is at (0,0,0), we need to make that assumption valid.

initialPosition = (0,0,0) # set initial camera position, tutorial does the re-positioning

The second customization is the Render method. This method is called if there is no SceneGraph present in the Context. (Such as in our tutorial).

def Render( self, mode): """Render the geometry for the scene."""

Prevents OpenGL from removing faces which face backward

glDisable( GL_CULL_FACE )

Moves the drawing origin 6 units into the screen and 1.5 units to the left

glTranslatef(-1.5,0.0,-6.0);

Starts the (legacy) geometry generation mode

glBegin(GL_TRIANGLES) glVertex3f( 0.0, 1.0, 0.0) glVertex3f(-1.0, -1.0, 0.0) glVertex3f( 1.0, -1.0, 0.0) glEnd()

Moves the drawing origin again, cumulative change is now (1.5,0.0,6.0)

glTranslatef(3.0,0.0,0.0);

Starts a different geometry generation mode

glBegin(GL_QUADS) glVertex3f(-1.0,-1.0, 0.0) glVertex3f( 1.0,-1.0, 0.0) glVertex3f( 1.0, 1.0, 0.0) glVertex3f(-1.0, 1.0, 0.0) glEnd(); if __name__ == "__main__": TestContext.ContextMainLoop()

Author: Jeff Molofee (aka NeHe)

If you plan to put this program on your web page or a cdrom of any sort, let me know via email, I'm curious to see where it ends up :)

If you use the code for your own projects please give me credit, or mention my web site somewhere in your program or it's docs.