[Marble-devel] Review Request: introduce optimized code path for Mercator projection

[Bernhard Beschow]

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http://svn.reviewboard.kde.org/r/6109/
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Review request for marble.


Summary
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This patch introduces an optimized code path for the case that both the tile projection and the map projection are of type Mercator. In this very common case, the tiles can be scaled rather than reprojected, promising a significant speedup. Moreover, it seems to avoid crashes in high zoom levels on the N900.


Diffs
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  /trunk/KDE/kdeedu/marble/src/lib/AbstractScanlineTextureMapper.h 1205882 
  /trunk/KDE/kdeedu/marble/src/lib/AbstractScanlineTextureMapper.cpp 1205882 
  /trunk/KDE/kdeedu/marble/src/lib/CMakeLists.txt 1205882 
  /trunk/KDE/kdeedu/marble/src/lib/FastMercatorTextureMapper.h PRE-CREATION 
  /trunk/KDE/kdeedu/marble/src/lib/FastMercatorTextureMapper.cpp PRE-CREATION 
  /trunk/KDE/kdeedu/marble/src/lib/TextureLayer.cpp 1205882 

Diff: http://svn.reviewboard.kde.org/r/6109/diff


Testing
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I have measured speedups of up to 2.7 on my system. This seems to depend on the QImage::Format, so format conversion should be avoided in a future version if possible.
The image quality is roughly of outline quality when a discrete zoom level isn't hit.


Thanks,

Bernhard

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