OpenGL is an open standard, cross platform, advanced graphic library. It uses the graphic cards processor (GPU) and memory, to speed up applications. With OpenCPN a user with a typical modern graphic card will have an enhanced experience. Much faster and smoother zooming and panning as well as clearer and sharper chart rendering.
In OpenCPN, OpenGL is a choice; however. the old graphic engine is still there. OpenGL will not work for everyone. Performance may not be improved with embedded graphics chips, often found in older laptops and netbooks.
Microsoft has gone from support to hostility towards OpenGL. There is currently a lot of trouble in Windows for all OpenGL applications, not just OpenCPN. OpenCPN has been forced to disable a handful of OpenGL features for all Intel OpenGL graphics drivers on Windows, for example.
Mac OS X has full supports for OpenGL.
For Linux the situation is slightly different. Linux supports OpenGL, as it generally tends to support open standards. The user is however dependent on a driver from the graphic cards maker, and their support for OpenGL. This may change with projects like nouveau, a free driver for nVidias cards.
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Without OpenGL and With OpenGL
Heavy over zooming reveals some of the secrets behind OpenGL
The main reasons are:
OpenCPNs performance with OpenGL is highly dependent upon your graphics hardware and drivers.
Start using OpenGL
If you have a lot of graphic memory, or very little, try to add the following to your config (.ini on windows) file:
[Settings] .... GPUMemorySize=nnn
where nnn is graphics card memory size, in MBytes. 256 MBytes is the default.
Troubles in OpenGL mode?**
This free adapter testing software is for various operating systems, including Windows 32bit and 64bit.
GLview: OpenGL Extensions Viewer http://www.realtech-vr.com/glview/
This software tool tests your graphics card capabilities and makes a report log. It is useful in tracking down particular problems with OpenGL on a given system. The Developers can then help determine what is wrong.
However when other software like GoogleEarth works OK with OpenGL on, then there are possibly other reasons why OpenCPN fails, related to the Opencpn OpenGL implimentation. There are many, many graphics cards and they have differing capabilities and sometimes the Opencpn opengl implimentation has to be adjusted for a particular card.