Hi Alexander,
This filter on rbg (0,0,0) value is done to enable VPB to problem
merge reprojected imagery that no longer aligns along regular
boundaries of the image but instead is surrounded by an irregular
black border. The reprojection itself is done by GDAL.
Robert.
On Wed, Aug 11, 2010 at 1:19 PM, Alexander Irion <alexander.ir...@xse.de> wrote:
> Hi,
>
> I use osgdem with a dummy tile of height zero and the --whole-globe flag set
> to get the whole earth generated. If I add a texture with parameter -t the
> black parts of the texture will be translucent and in the resulting texture
> the color (light grey) of my dummy tile is used instead. See the result in
> the attached picture "srtm_L3_X3_Y3_incorrect.jpg".
>
> I found the reason for this in the following if statement in line 796 of
> SourceData.cpp:
>
> …
> else if (sourceColumnPtr[0]!=0 || sourceColumnPtr[1]!=0 ||
> sourceColumnPtr[2]!=0)
> {
> destinationColumnPtr[0] = sourceColumnPtr[0];
> destinationColumnPtr[1] = sourceColumnPtr[1];
> destinationColumnPtr[2] = sourceColumnPtr[2];
> if (destination_hasAlpha)
> destinationColumnPtr[3] = 255;
> }
> …
>
> The if statement causes the color value only be taken, if it is not black
> (r=0, g=0, b=0). Commenting out the condition yields in the correct result,
> shown in picture "srtm_L3_X3_Y3_correct.jpg".
>
> Now, I wonder what the purpose of this if statement was?
>
> Regards,
> Alex
>
> ------------------
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=30688#30688
>
>
>
>
> Attachments:
> http://forum.openscenegraph.org//files/srtm_l3_x3_y3_correct_163.jpg
> http://forum.openscenegraph.org//files/srtm_l3_x3_y3_incorrect_598.jpg
>
>
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