Celestia Forums

With the enormously improved smoothness that one obtains from calculating the texture normals (gradients) from 16bit precision elevation maps, instead of merely 8bit, one seems to be approaching the limits of capabilities of DXT-compression! Same for JPG's but this will surpeise nobody.

Here is a comparison. I displayed a tiny piece of the 8k-sized MOLA normal maps of Mars over a uniformly white main texture. With the default FoV (~30 deg) I display them at only 400 km distance, so a very high magnification is involved. All normal maps are derived from the same 16bit nm16-generated *.PNG master texture!

First the *.PNG original, which is amazing in its smoothness despite the huge magnification:



Next the 24bit-color DXT3 encoded normal map (using nvdxt.exe):


Finally a 85% quality JPG compression



I guess the conclusions are obvious! DXT5 encoding does not give much better results.

Bye Fridger

Is this an example of the 4x4 texel limitation that Jens wrote about in http://63.224.48.65/forum/viewtopic.php?t=2813 ?

selden wrote:Is this an example of the 4x4 texel limitation that Jens wrote about in http://63.224.48.65/forum/viewtopic.php?t=2813 ?

Yes, unfortunately. I should have mentioned it. My point here was to illustrate specifically that for our new 16bit type quality level we DO need a new compression urgently.

Perhaps Jens 8bit paletted format is much better?

At least we have to envisage something, otherwise we cannot really exploit the gain in quality in practice....

Bye Fridger

Hi Fridger,

that's exact the problem that I have since few month. Look at my old post:

http://celestiaproject.net/forum/viewtopic.php?t=1989

But I think the day will come where we have solved all these problems and bugs with bumpmapping .

Bye Jens

jim wrote:Hi Fridger,

that's exact the problem that I have since few month. Look at my old post:

http://celestiaproject.net/forum/viewtopic.php?t=1989

But I think the day will come where we have solved all these problems and bugs with bumpmapping .

Bye Jens

Thats what Ive been waiting for...

Jim, Rass,

But dont'get me wrong: I think that the problem displayed in the above pictures has become really bad only recently, due to the fact that those new high-quality 16bit maps may now be zoomed so much more in principle that the gap to DXT encoded quality becomes intolerably large.

While there were also some problems before here and there, they were much less visible when starting off with only 8bit quality!

Bye Fridger