[gdal-dev] Support for Terrain-RGB

[Rahkonen Jukka]

Hi,

The encoding system does not care if the source data presents DEM or something else. Also, it does not need to be restricted to RGB. I tried to find similar use cases and it looks like encoding 32 bit floats into RGBA (or RG for 16 bits) was used with WebGL shaders when floats were not supported natively. See for example https://www.shadertoy.com/view/WsVGzm, https://gamedev.net/forums/topic/630239-encode-float-to-rg-or-rgb/, https://github.com/equinor/glsl-float-to-rgba

-Jukka Rahkonen-

________________________________________
Lähettäjä: gdal-dev <gdal-dev-bounces at lists.osgeo.org> käyttäjän Andrey VI via gdal-dev <gdal-dev at lists.osgeo.org> puolesta
Lähetetty: Perjantai 9. tammikuuta 2026 9.02
Vastaanottaja: rayg <rayg at daylongraphics.com>
Kopio: gdal-dev <gdal-dev at lists.osgeo.org>
Aihe: Re: [gdal-dev] Support for Terrain-RGB

Why not just "rgb-dem", i.e. "RGB encoded DEM"? Friday, January 9, 2026 3:16 AM +03:00 from rayg via gdal-dev <gdal-dev at lists.osgeo.org>: Maybe call it "scalar-rgb"? Because ultimately what the encoding does is use the color channels to hold a single value. It doesn't even have to be for elevations at all. Could also add swizzle options in case BGR or some other order is used. And include the alpha channel just in case, but also let alpha be alpha if needed. If e.g. "A" is left off from the swizzle option, then it's an actual alpha channel. More general would be scalar encoding of any multichannel (multiband) file, e.g. YCbCr, HSV, CMYK, etc. Ray On Thu, 8 Jan 2026 at 1:13 PM Even wrote:>
> There's nothing especially terrain (or topography) about this afaics, 
> and utility seems like the right approach rather than creating a 
> format variant.

Actually Frédéric's intersting remark abou potential usage with "gdal 
raster tile" would actually make the driver approach a better 
choice....   unless we would extend "gdal raster tile" to accept a 
pipeline to go to create a final tile from a 'raw' one, like 'gdal 
raster tile --tile-pipeline="read ! encode-rgb --offset=-10000 ! write 
--of PNG" --extension png  in.tif out_directory' .

But a ENCODE_RGB driver approach is more simple than implementing that.

Even

-- 
http://www.spatialys.com
My software is free, but my time generally not.

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