OpenGL ES Libraries

Want to start developing for the Nokia N900 using OpenGL ES but don't know where to start?

Here is some information about the various libraries and APIs that are available on the N900. Also included is information about developing with OpenGL ES and some examples.

Contents

Library Support

This section includes a partial list of library options for using OpenGL ES.

SDL 1.2

The N900 ships with SDL 1.2. You can use that and a external library, SDL-GLES (available in extras), to create simple OpenGL ES 1.1 and 2.0 applications.

SDL 1.3

SDL 1.3 supports OpenGL ES 1.x. This doesn't seem to work in the N900 as of now.

OpenGL ES 1.x utilies

Information:

http://www.unrealvoodoo.org/hiteck/projects/maemo/

Git repositories:

http://www.unrealvoodoo.org/git/

Sami Kyöstilä has developed a number of utilities. This includes SDL with OpenGL ES 1.x support, libglutes, python-opengles and several translators to convert OpenGL ES and OpenGL. Note that these utilities are designed for the Nokia N810 and OpenGL ES 1.x.

Qt

You can use Qt with OpenGL ES 2.x on the Nokia N900. There is an example application called hellogl_es2. Get it here:

http://qt.gitorious.org/qt/qt/trees/4.5/examples/opengl/hellogl_es2

This example shows how to use OpenGL ES embedded in a QtWidget.

Clutter

libclutter supports OpenGL ES 2.x. It seems oriented towards toolkits and applications with user interface elements.

Xlib (X11)

You can use Xlib (X11) and utilize the EGL library for context creation along with OpenGL ES. This is what the Bounce Evolution game uses.

You can use OpenGL ES version 1 or 2 directly without worrying about the version that is supported by the library.

See below for an example Xlib application.

PVRShell

The Khronos OpenGL ES 2.0 SDK includes a simple API for window creation called PVRShell. They also include additional tools for more advanced computer graphics applications. It is much simpler to create an OpenGL ES 2.0 application using PVRShell. It doesn't seem to have much support for handling events.

Notes

  • OpenGL and OpenGL ES are very different and are not compatible.
  • WARNING: If you try to run an OpenGL application with scratchbox then it will most likely work. This is because it uses the native operating system OpenGL libraries to execute. However, if you try and run it on the device it will not work as it only has OpenGL ES libraries.
  • OpenGL ES doesn't run natively on a desktop computer. It is possible to get some kind of emulation library from the PowerVR Insider SDK [1] so that you can test on a desktop computer. The OpenGL ES 2.0 emulation library was packaged for use inside the FREMANTLE_X86 scratchbox target (package libgles2-dev, extras-devel non-free repository).
  • OpenGL ES 1.x and OpenGL ES 2.x are also different. OpenGL ES 1.x has a fixed pipeline whereas OpenGL ES 2.x uses shaders. The matrix stack has also been removed and you have to manage it yourself.
  • If you require any kind of performance in Maemo 5, you need to make your window full screen.

Installation and Examples

Here are some notes about packages required for OpenGL ES development and some simple examples to help get you started.

You can compile OpenGL ES applications with scratchbox. The ESBox IDE makes it much easier to execute the application on the device. It automates copying the binary onto the device and execution.

Firstly you want to install the following packages on scratchbox.

[sbox-FREMANTLE_ARMEL: ~] > fakeroot apt-get install libgles2-sgx-img-dev

This is the OpenGL ES 2.0 development files required for compiling.

[sbox-FREMANTLE_ARMEL: ~] > fakeroot apt-get install opengles-sgx-img-common-dev

This installs the EGL library (used for portable context creation, see the docs) and PowerVR development files. It also includes some simple demos.

If you want OpenGL ES 1.x compatibility then install the following package in scratchbox:

[sbox-FREMANTLE_ARMEL: ~] > fakeroot apt-get install libgles1-sgx-img-dev

Now install the required libraries on the N900:

Nokia-N900-42-11:~# apt-get install libgles1-sgx-img libgles2-sgx-img opengles-sgx-img-common


Qt Example

You need to install libqt4-opengl-dev:

[sbox-FREMANTLE_ARMEL: ~] > fakeroot apt-get install libqt4-opengl-dev

It doesn't install any examples, so download the hellogl_es2 example from here:

http://qt.gitorious.org/qt/qt/trees/4.5/examples/opengl/hellogl_es2

Moddify glwidget.h and change #include <QGLWidget> to #include <QtOpenGL/QGLWidget>.

Edit the hellogl_es2.pro and add:

LIBS += -lGLESv2 -lQtOpenGL
Then run:
qmake -project
qmake
make

Which will (hopefully) compile hellogl_es2. Then you can copy the binary to the device and run it.

Xlib Examples

You can usually compile any Xlib example with a simple Makefile like:

CC=g++
LDLIBS=-lEGL -lX11 -lGLESv2 
all: main
main: main.o

In the PowerVR SDK TrainingCourse directory there are a number of examples. The first two use only Xlib. The rest make use of PowerVR libraries which have to be linked in with the program.

Here is a nice simple example (created by exoticorn)

Resources

Here are some useful resources.