[gdal-dev] GSoC GDAL2Tiles: Opacity for Google Maps Overlay, Embedded Google Earth, Tile generation

Lucena, Ivan ivan.lucena at pmldnet.com
Wed Aug 13 07:56:34 EDT 2008

Hi Vincent,

I found someone having the same complain on WorldWind forum but the 
complainer call it "lost of resolution". :)

I also found the OpenGL code where you can change that behavior. There 
is a function called glTextParameteri() where the last parameter tells 
OpenGL which magnifier filter to use: GL_NEAREST or GL_LINEAR.

In my implementation I don't access that function directly but through a 
3D component that does that. But I expose that option to the user on a 
right-click popup-menu. "Power to the user!"

Anyway, Thanks for you suggestion. It seams to work.

Best regards,


Vincent Schut wrote:
> Hi Ivan, Klokan,
> Lucena, Ivan wrote:
>> Hi Klokan,
>> Would you mind if I extend your message tread a little bit?
>> The GDAL2Tiles is a great tool and it just getting better, 
>> congratulation.
>> But I have some end-user complain that they don't like to see the 
>> pixel blended when you get very close to then. Those folks really want 
>> to see the big square blocks of their images classification on top of 
>> Google Earth images. That is not your fault of course. That is a nice 
>> feature on GE, a anti-aliasing rendering technique that probably 
>> attend the general public. I have spoken with Google about that but it 
>> didn't resonate. As far as I can remember (from OpenGL project that I 
>> worked in the past) this problem could be easily solved with just a 
>> parameter change on the texture-surface-rendering definition. I may be 
>> wrong.
>> My question is, do you know if there is any way to change that 
>> behavior on GE? Doesn't look like you can change that option through 
>> the API as a plugin, does it? Or maybe there is something you can do 
>> on the KML.
>> By the way, does any one have ever received that request from users?
>> Best regards,
>> Ivan
> <big snip>
> It does resonate here :)
> I have been publishing deforestation maps with GE (using a home-brewn
> gdal-python script), and had the same complaints. I don't want my
> classes to mix. An area is either forest, or non-forest, or deforested,
> and nothing in between. O how nice it is to force your own will upon
> reality :-)
> The way I 'solved' this was by adding subsampled tiles, which
> effectively prevent GE to start antialiasing to soon. So my highest
> resolution tiles are in fact higher resolution than the real full
> resolution. This of course is just a workaround and just works if the
> user does not zoom in too much, but in my experience it improved the
> users' feeling a lot.
> I must say I am very interested in a better way to force GE to not
> antialias raster overlays.
> Regards,
> Vincent Schut.
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