New Site

I created a new site to which I am moving all the tutorials. It allows a much more logical layout for tutorials than a blog.

The URL for now is http://sites.google.com/site/naltai3/, but it may change in the future I guess.

This site will no longer be updated.

Thanks for your patience and sorry for the hiatus.

Naltai

Back Again

Life is hectic, of course. Nevertheless I had a couple of spare hours today, so I finished separating the framework and updated all of the code to use it. Also, as you will see below, I wrote up a quick appendix about the framework. All comments appreciated.

Hopefully it won't be so long until I get the next item (The first tutorial!) up.

By the way, price, if you could shoot your modified code for pyglet back, that would be great.

Till Next Time,
Naltai

Appendix B: Framework

This appendix describes the framework code that interacts with the operating system in order to give us somewhere to draw with OpenGL, as well as a way to interact with the user. The framework for pybsp is very simple, doing the minimum to show a window and allow the user some measure of camera control. This is intentional, to keep the focus on the OpenGL code. For this reason basic features you would normally find in a framework such as window resizing, mouse handling and display loops are not supported.

The pybsp framework is written against the wxwindows library for python. This library is freely available, cross platform, and relatively easy to use. In addition it is easy to set up an OpenGL window for use. The library and its documentation can be found at www.wxpython.org.

The main function pretty much says it all:

def main(pybsp):
   """Create a simple wx application to show our opengl drawing and allow simple camera commands"""
   app = wx.PySimpleApp()
   frame = wx.Frame(None,-1,'PyBSP',wx.DefaultPosition,(400,400))
   canvas = myGLCanvas(frame)
   canvas.pybsp = pybsp
   frame.Show()

Create a wx application. Create a 400 by 400 window with the title PyBSP. Create a Custom GL Canvas to fill the window. Tell the custom canvas the pybsp object to use (contains the tutorial code). Show the window.

The custom GL Canvas is basically a wrapper around the GLCanvas object that calls out to the pybsp object for drawing and GL initialization. It handles two events: the paint event and the keydown event.

On the paint event the framework checks if the pybsp object has initialised OpenGL. If not it calls the OnInit function in the pybsp object. On normal execution it sets up the canvas for drawing using wx calls, calls the OnDraw function in the pybsp object to draw the screen, then calls wx to finish the drawing. In addition it times the OnDraw function as a simple performance metric.

On the keydown event, keystrokes are interpreted to move the camera. The camera is tracked with a simple x,y,z position, a direction angle that indicates the direction the camera is pointing in the xy plane, and an updown angle which indicates the direction above or below the horizon that the camera is pointing. The key press routine interprets the arrow keys to modify the camera's direction by 5 degrees on the appropriate axis, whilst the w,a,s and d keys move it forwards, left, backwards and right along the line of sight of the camera respectively. After updating the camera position, wx is asked to repaint the display, thus invoking the OnDraw function in the pybsp object again from the paint event handler.

Till Next time,
Naltai

Life Intrudes Again

I've been very busy at work and at home for the past week, so not much has been done. About the only progress is some refactoring of the code to separate all of the wx windows GUI code from the opengl code. This is in preparation to writing the tutorials so that the tutorials can completely focus on the opengl code. When the refactoring is complete (I've only done one file so far) I will write an explanation of the framework code similar to the parser code.

The next two weeks don't look good for progress either with the olympics on TV.

Oh Well,

Till next time,
Naltai