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GemRB with high quality screen scaling


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Please see post here: http://www.vogons.org/viewtopic.php?f=5&t=38256. The GemRB client will support the OpenGL-HQ driver (high quality screen scaler) via the SDL library. It requires GemRB installed correctly, a custom version of the SDL.dll file, and a batch file to enable the openglhq driver. The replacement SDL.dll file is here: http://www.vogons.org/download/file.php?id=13835. The batch file would be created with the following lines and named "gemrb.bat":

set SDL_VIDEODRIVER=openglhq



Then, run gemrb.bat to enable openglhq; given the custom SDL.dll file replaced the original one. Note these are Windows instructions, but this setup will work on all GemRB supported operating systems albeit with a few changes in these steps.


This OpenGL-HQ driver is described at this web site: http://www.syntax-k.de/projekte/sdl-opengl-hq. The author is a brilliant programmer and understands the underlying hardware systems. His scaler brings fast scaling via instructions sent to the video card directly and also a very high quality smoothing of the scaled/stretched image of the game.

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The above opengl-hq driver is not in SDL2, it is for SDL1.x. The opengl-hq driver is a real and already available opengl driver for use with the default GemRB installation. It was developed over several years and is used in many open source projects. The driver produces high quality scaling at a fast speed via the OGL video hardware.

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Did you notice, while looking Imoen and Xzar's in the above pictures that their characters "stand" in a wrong position related to their character circles ? Well, more than the charname and Montaro... the reason being that their character is larger and thus their characters animation which is a .bam is bit off centered by the scaling action... a dragon is likely to look like it's floating on top of the circle.

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The OpenGL-HQ scaling is best observed in the GemRB client and not from an exported image. However, I uploaded another image for viewing; this one has pixel dimensions closer to integer scaling: http://www.vogons.org/download/file.php?id=13905. I no longer have BG1 installed in GemRB, so this was the only image I had to export, but others may follow the instructions in the parent post so they observe the true effect of the high quality image. I haven't seen any examples of GemRB with SDL 2.0 OGL scaling, however, to compare with. In the case that this sort of scaling is available, it will integer scale but it would not provide the high quality smoothing of OpenGL-HQ (Hqx or higher).


There is some information on image processing here: http://en.wikipedia.org/wiki/Hqx ; so the image appears clearer on screen and the image pixelation is reduced, although there are other benefits to high quality scaling. This is done in many popular emulators and users should test for themselves (where the video driver is available to make comparisons).

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