pi3d 1.3a

pi3d OpenGLES2 3D graphics library

Introduction to Pi3D

Pi3D written by Tim Skillman, Paddy Gaunt, Tom Ritchford Copyright (c) 2013

There’s plenty of 3D code flying around at the moment for the Raspberry Pi, but much of it is rather complicated to understand and most of it can sit under the bonnet!

pi3d is a Python module that aims to greatly simplify writing 3D in Python whilst giving access to the power of the Raspberry Pi GPU. It enables both 3D and 2D rendering and aims to provide a host of exciting commands to load in textured/animated models, create fractal landscapes, shaders and much more.

v1.3 release of the pi3d module now adds support for running on platforms other than the raspberry pi (X on linux) and runs with python 3 as well as 2 The OpenGLES2.0 functionality of the Raspberry Pi is used directly or via mesa on ‘big’ machines. This makes it generally faster and opens up the world of shaders that allow effects such as normal and reflection maps, blurring and many others. It has various demos of built-in shapes, landscapes, model loading, walk-about camera and much more! See the demos included with this code and experiment with them ..

If you are reading this document as the ReadMe in the repository then you can find the full version of the documentation here http://pi3d.github.com/html/index.html

Demos for Pi3D are now stored at https://github.com/pi3d/pi3d_demos

N.B. Shaders are now integrated into programs differently. The syntax used to be:

myshader = pi3d.Shader('shaders/uv_flat')

and is now:

myshader = pi3d.Shader('uv_flat')

this will use the default shaders ‘bundled’ with the package. The old format will be interpreted as ‘look in a subdirectory of the directory where the demo is being run from.’ This is probably what you would do if you rolled your own special shaders for your own project.

Download, Extract and install

If you have pip installed you should be able to open a terminal and type:

sudo pip install pi3d

Otherwise you can download from https://pypi.python.org/pypi/pi3d and extract the package then in a terminal:

sudo python setup.py install

(or you may need to use python3) this will put the package into the relevant location on your device (for instance /usr/local/lib/python2.7/dist-packages/) allowing it to be imported by your applications.

The latest code can be obtained from https://github.com/tipam/pi3d/ where there is a Download ZIP link, or you can install git then clone using git clone https://github.com/tipam/pi3d.git this git method will give you the option to update the code by running, from the pi3d directory git pull origin master

Setup on the Raspberry Pi

1. Memory Split setup

   Although most demos work on 64MB of memory, you are strongly advised to have a 128MB of graphics memory split, especially for full-screen 3D graphics. In the latest Raspbian build you need to either run sudo raspi-config or edit the config.txt file (in the boot directory) and set the variable gpu_mem=128 for 128MB of graphics memory.

2. Install Python Imaging

   Before trying any of the demos or Pi3D, you must download the Python Imaging Library as this is needed for importing any graphics used by Pi3. The original Imaging library is no longer really maintained and doesn’t run on python_3. The better equivalent replacement is Pillow however a couple of issues relating to text vertical alignment will not be corrected unti the Oct2013 issue. To install Pillow you need to:

   sudo apt-get install python-dev python-setuptools libjpeg-dev zlib1g-dev libpng12-dev libfreetype6-dev
   sudo apt-get install python-pip
   sudo pip install Pillow
   ...

   If you miss any of the dependent libraries and need to add them later you will have to pip uninstall then re pip install

   For python_3 support the first above will provide the required graphics libraries used by Pillow but you will need to swap to python3-dev and python3-setuptools also pip is different:

   sudo apt-get install python3-pip
   sudo pip-3.2 install Pillow

   If you do not intend to run python_3 and need nicely aligned text strings over the short term you can install the old PIL: on the terminal, type:

   sudo apt-get install python-imaging

   If you later switch to Pillow you will need to sudo remove python-imaging first

   [To run on Arch linux you will need to install:

   pacman -S python2
   pacman -S python-imaging
   pacman -S python2-numpy

   this worked for me. Presumably you would need the pacman equivalent of all the installations outlined above for Pillow and python_3]

Setup on alternative Linux platforms

1. The machine will need to have a gpu that runs OpenGL2+ and obviously it will need to have python installed. If the Linux is running in vmware you will need to ‘enable 3d acceleration’. You need to install libraries that emulate OpenGLES behaviour for the gpu:

   sudo apt-get install mesa-utils-extra

   This should install libEGL.so.1 and libGLESv2.so.2 if these change (which I suppose they could in time) then the references will need to be altered in pi3d/constants/__init__.py

   The installation of PIL or Pillow should be the same as above but you are more likely to need to manually install python-numpy or python3-numpy

Editing scripts and running

1. Install Geany to run Pi3D

   Although you can use any editor and run the scripts in a terminal using python, Geany is by far the easiest and most compatible application to use for creating and running Python scripts. Download and install it with:

   sudo apt-get install geany xterm

2. Optionally, install tk.

   Some of the demos require the tk graphics toolkit. To download and install it:

   sudo apt-get install tk

3. Load and run

   Either run from the terminal python3 ~/pi3d/demos/Minimal.py or load any of the demos into Geany and run (using the cogs icon). As a minimum, scripts need these elements in order to use the pi3d library:

   import pi3d
   DISPLAY = pi3d.Display.create(w=128, h=128)
   shader = pi3d.Shader("2d_flat")
   sprite = pi3d.ImageSprite("textures/PATRN.PNG", shader)
   while DISPLAY.loop_running():
     sprite.draw()

   But.. a real application will need other code to actually do something, for instance to get user input in order to stop the program!

A Very Brief Explanation

The whole idea of Pi3d is that you don’t have to get involved in too many of the nuts and bolts of how the OpenGL graphics processor works however it might help to get an overview of the layout of Pi3d. More detailed explanations can be found in the documentation of each of the modules. Read http://pi3d.github.io/html/FAQ.html before you try anything ambitious or if anything goes wrong, obviously. There is a http://pi3d.github.io/html/GPUexplain.html where I try to explain in some more detail what is going on.

Display The Display class is the core and is used to hold screen dimension information, to initiate the graphics functionality and for ‘central’ information, such as timing, for the animation. There needs to be an instance of Display in existence before some of the other objects are created so it’s a good idea to create one first job.

Shape All objects to be drawn by Pi3d inherit from the Shape class which holds details of position, rotation, scale as well as specific data needed for drawing the shape. Each Shape contains an array of Buffer objects; normally only containing one but there could be more in complicated models created with external 3D applications.

Buffer The Buffer objects contain the arrays of values representing vertices, normals, faces and texture coordinates in a form that can be quickly read by the graphics processor. Each Buffer object within a Shape can be textured using a different image or shade (RGB) value and, if needed, a different Shader

Shader The Shader class is used to compile very fast programs that are run on the graphics processor. They have two parts: Vertex Shaders that do calculation for each of the vertices of the Buffer and Fragment Shaders applied to each pixel. In Pi3d we have kept the shaders out of the main python files and divided them using the two extensions .vs and .fs The shader language is C like, very clever indeed, but rather hard to fathom out.

Camera In order to draw a Shape on the Display the Shader needs to be passed the vertex information in the Buffers and needs know how the Shape has been moved. But it also needs to know how the Camera has moved. The Camera class generally has just one instance and if you do not create one explicitly then Display will generate a default one when you first try to draw something. The Camera has position and rotation information similar to Shapes but also information to create the view, such as how wide-angle or telephoto the lens is.

Texture The Texture objects are used to load images from file into a form that can be passed to the Shader to draw onto a surface. They can also be applied as normal maps to give much finer local detail or as reflection maps - a much faster way to make surfaces look shiny than ray tracing.

Light To produce a 3D appearance most of the Shaders use directional lighting and if you draw a Shape without creating a Light a default instance will be created by the Display. The Light has properties defining the direction, the colour (and strength i.e. RGB values) and ambient colour (and strength).

When you look through the demos you will see one or two things that may not be immediately obvious. All the demos start with:

#!/usr/bin/python
from __future__ import absolute_import, division, print_function, unicode_literals

Although these lines can often be left out, the first tells any process running the file as a script that it’s python and the second is basically to help the transition of this code to run using python 3:

import demo

Allows the demo files to be put in a subdirectory but still run. If you write a program in the top directory then you will need to take this out:

import pi3d

Is an alternative to importing just what you need i.e.:

from pi3d.constants import *
from pi3d import Display
from pi3d.Texture import Texture
from pi3d.Keyboard import Keyboard
from pi3d.Light import Light
from pi3d.Shader import Shader
from pi3d.util.String import String
...
from pi3d.shape.Sphere import Sphere
from pi3d.shape.Sprite import Sprite

If you import the whole lot using import pi3d then you need to prefix classes and functions with pi3d. And you are loading a large number of variable names which might cause a conflict, isn’t as explicit and is less tidy (in the non- superficial sense)! A third way to import the modules would be to use from pi3d import * this saves having to use the pi3d. prefix but is much harder to debug if there is a name conflict.

Documentation

see http://pi3d.github.io/html/index.html

Please note that Pi3D functions may change significantly during its development.

Bug reports, comments, feature requests and fixes are most welcome!

Please email on [e-mail] or contact us through the Raspberry Pi forums or on http://pi3d.github.com/html/index.html

Acknowledgements

Pi3D started with code based on Peter de Rivaz ‘pyopengles’ (https://github.com/peterderivaz/pyopengles) with some tweaking from Jon Macey’s code (jonmacey.blogspot.co.uk/2012/06/).

Many Thanks, especially to Peter de Rivaz, Jon Macey, Richar Urwin, Peter Hess, David Wallin and others who have contributed to Pi3D - keep up the good work!

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