A very nice Cassini image of Enceladus

[Chuft-Captain]

http://saturn.jpl.nasa.gov/photos/image ... ageid=3344

[ElChristou]

Nice shot!
The surface features are really strong! Seems we need a good normalmap...

[t00fri]

Here is how the same view looks with my recent 4k Enceladus texture for Celestia.Sci:
http://forum.celestialmatters.org/viewtopic.php?t=300

It's the same flyby configuration of Oct 5 2008, but there are NO "enhanced colors"...
The image is strongly reduced in size/resolution, though...



Fridger

[ElChristou]

Here is how the same view looks with my recent 4k Enceladus texture for Celestia.Sci...

But still a normal map would be welcome; the deep "canyon" appear quite flat on a color map only rendering...

[chris]

Here is how the same view looks with my recent 4k Enceladus texture for Celestia.Sci...

But still a normal map would be welcome; the deep "canyon" appear quite flat on a color map only rendering...

There's hope... Take a look at the work that Bjorn Jonsson has done with Rhea:

http://www.unmannedspaceflight.com/inde ... topic=5931

--Chris

[t00fri]

Here is how the same view looks with my recent 4k Enceladus texture for Celestia.Sci...

But still a normal map would be welcome; the deep "canyon" appear quite flat on a color map only rendering...

No problem , here you go (never mind it's all fake, of course)



Fridger

[ElChristou]

...There's hope... Take a look at the work that Bjorn Jonsson has done with Rhea:...

Sounds promising...
One more thing we need here... A production line of normal maps... (I know, easy to say... )

[t00fri]

...There's hope... Take a look at the work that Bjorn Jonsson has done with Rhea:...

Sounds promising...
One more thing we need here... A production line of normal maps... (I know, easy to say... )

Christophe,

for proper normalmaps you need independent elevation measurements. I.e. one cannot derive normalmaps from standard textures by means of some software algorithms. If these independent measurements are lacking, there is no substitute, really.

We have agreed a long time ago that we shall NOT use fake normalmaps in Celestia, as produced by some "nm-generators" from a given texture.

Fridger

[ElChristou]

Christophe,

for proper normalmaps you need independent elevation measurements. I.e. one cannot derive normalmaps from standard textures by means of some software algorithms. If these independent measurements are lacking, there is no substitute, really.

We have agreed a long time ago that we shall NOT use fake normalmaps in Celestia, as produced by some "nm-generators" from a given texture.

This is not what I'm saying we should do. Now, I don't know much on the topic, but the DEM shown on Chris link is not a quick trick to simulate an elevation. It's actually the elevation one can interpolate from data available. I guess one could create a normal map from this work... (and again I believe it's not an easy task but eventually it would be great to have such workflow...)

[t00fri]

Christophe,

for proper normalmaps you need independent elevation measurements. I.e. one cannot derive normalmaps from standard textures by means of some software algorithms. If these independent measurements are lacking, there is no substitute, really.

We have agreed a long time ago that we shall NOT use fake normalmaps in Celestia, as produced by some "nm-generators" from a given texture.

This is not what I'm saying we should do. Now, I don't know much on the topic, but the DEM shown on Chris link is not a quick trick to simulate an elevation. It's actually the elevation one can interpolate from data available. I guess one could create a normal map from this work... (and again I believe it's not an easy task but eventually it would be great to have such workflow...)

Christophe,

BJ's method is not a quick trick, but nevertheless it is a familiar one to derive altitude information. As I wrote, there is NO way to do without! I suppose you realize that BJ's method requires for each view a PAIR of stereo images whose displacement allows to effectively reconstruct the elevation. Such specialized image pairs are indeed available sometimes. I have seen such red-green image pairs from Cassini before.

Incidentally, the method is effectively identical to some previous measurements of planetary/lunar elevations from satellites. It just sounds a little different
For example, the topography of the Moon has been measured by the methods of laser altimetry and stereo image analysis, most recently from data obtained during the Clementine mission.

I don't see how you imagine in practice a "workflow" for doing all this within the Celestia community. This requires a lot of specific know how and insider information about the imaging data. It's certainly harder than using ISIS3 for assembling planetary images in particular projections from raw data. As to ISIS3 only cartrite and myself worked with the available resources.

Fridger

[t00fri]

Christophe,

here is another argument that normalmaps are not too important for now in the official Celestia distribution:

As long as Celestia restricts it's hires texture distribution to max 4k sized images only, the rendered textures are necessarily to stay far away from the observer. (For close-ups you need a much better resolution like 64k or similar!).

As an example: The above beautiful Enceladus photo was taken at a distance of ONLY 25 km above the surface. Now we all know that with a texture resolution as low as 4k, 25 km is far too close to see anything sharply focussed!

+++++++++++++++++++++++
Hence at such far distances from the surface as required from the restriction to 4k textures, elevations are not really visible and normalmaps are thus rather unimportant => redundant!
+++++++++++++++++++++++

Fridger