Planet distance?

[helentr]

I was trying to make a Mars scene.
Not wanting to use the huge MOLA ones (which I haven't figured out yet BTW, despite Matt's explanations), I used the older and smaller DTM ones http://pdsimg.jpl.nasa.gov/data/vo1_vo2-m-vis-5-dtm-v1.0
I used 3DEM to save as TER and loaded into Terragen. So far, so good.
But Mars has a smaller radius than earth, so I changed the planet radius to 3397 km from 6000 something. The result was disastrous. The atmosphere disappeared and the terrain went wild. It took me some time to think of moving the camera away from the planet and see that the terrain was on a height of more than 3000 km.(Look at the first image)
Changing the planet distance to the same value as the radius, made the terrain "sit" on the planet surface. (See second image)
I thought planet distance only affected the planet distance from the camera, so by changing it, the planet would move further away, but that the terrain would stay on the planet (or at least planet 01).

I don't know if this is a bug or a feature (or maybe I haven't understood what planet distance means), but should be useful to anyone attempting to do a Mars render.

Helen

[rcallicotte]

Planet radius is 6.378e+006 and the center of the default planet is -6.378e+006.  The planet distance is therefore the distance from the default camera to the center of the default planet.

[Will]

hmm thats good to know, I wish it was distance from the sun though (I know the sun is not an acual object in Terregen).

Regards,

Will

[helentr]

Well, what you say makes sense.
But, why should the distance from the center of the planet to the camera (both default), or - in other words - from point "zero" (0,0,0), affect the terrain placement? Doesn't the terrain sit on the -default- planet? That is what appears from the node network.

Helen

[rcallicotte]

Helen, that's the part I don't completely understand.  If the sun were an actual object, then everything else (in my opinion) would make easier sense.  But, like Will said, the TG2 sun is spoofed. 

This part "seems" like a bug - "Changing the planet distance to the same value as the radius..."

[helentr]

The sun isn't an actual object - it is a point distant light source. This is something many 3D programs use AFAIK (POV-Ray, BMRT and probably Blender).
In Terragen, it seems strange, because we are dealing with planets and would like the sun(s) to be actual objects.
So, I can understand that part, although I wish it were different. Maybe then, the sun would look better, if included in the image.
This "flying terrain" problem, also happens with a fractal terrain, although I haven't been able to find a point of view that would show it from afar. As soon as you change the planet radius to a smaller number, after you have added a fractal terrain, the camera goes underground.

Helen

[Will]

I was expermenting with using light sources as a sun a while back, it works just as well as the currerent system and it would make distace and easyer thing.

Regards,

Will

[dhavalmistry]

maybe you wanna check this post out!

http://forums.planetside.co.uk/index.php?topic=1256.msg12582#msg12582