## Planet coordinates

Started by rcallicotte, February 28, 2007, 02:41:25 pm

#### rcallicotte

##### February 28, 2007, 02:41:25 pm
How do the planet Heading, Elevation, and Distance values relate to the Centre coordinates as far as geometry calculations?  I'm no mathematician, so I need it in easy terms, if you can.
So this is Disney World.  Can we live here?

#### Oshyan

##### February 28, 2007, 03:34:15 pm #1
These settings are relative to the 0,0,0 coordinate origin that starts on the surface of the planet in the default scene and are referenced from the center of the planet itself. That's why the distance starts out as 6.378e+006, which is exactly equal to the radius - or one half the diameter of the planet - placing the 0,0,0 point just on the surface of the planet.

Distance simply controls the distance of the center of the planet from 0,0,0. Elevation is elevation of the planet above or below the x,z plane relative to the 0,0,0 coordinate origin. Heading is essentially the same - 360 degrees of heading relative to 0,0,0. These are all similar to the sun controls incidentally. Thus if the planet is *at* 0,0,0 Elevation and Heading have no effect. So you can't use these controls to rotate the planet. The effect is greater the further distant from 0,0,0 the planet is.

- Oshyan

#### rcallicotte

##### February 28, 2007, 03:42:33 pm #2
Thanks, Oshyan.

Is this true for planet objects I create or is everything created (for example, more planets) referenced to that 0, 0, 0 on the first planet?
So this is Disney World.  Can we live here?

#### Oshyan

##### February 28, 2007, 03:50:39 pm #3
Everything should be relative to 0,0,0, the coordinate origin.

- Oshyan

#### rcallicotte

##### February 28, 2007, 03:55:59 pm #4
Thanks!
So this is Disney World.  Can we live here?

#### Will

##### February 28, 2007, 04:04:28 pm #5
A question about craters. If you put them on the side of anouther planets thats not at 0,0 do they still work?

Regards,

Will
The world is round... so you have to use spherical projection.

#### Oshyan

##### February 28, 2007, 04:50:09 pm #6
I haven't had much luck getting crater shaders to work on other planets, but that doesn't mean it's not possible.

- Oshyan

#### Will

##### February 28, 2007, 04:52:48 pm #7
darn...anyone else have an idea on how to get this to work?

Regards,

Will
The world is round... so you have to use spherical projection.

#### Arandil

##### March 01, 2007, 09:36:46 pm #8
Quote from: calico on February 28, 2007, 02:41:25 pm
How do the planet Heading, Elevation, and Distance values relate to the Centre coordinates as far as geometry calculations?  I'm no mathematician, so I need it in easy terms, if you can.

I believe you can consider the values to represent the x, y, z offset from 0, 0, 0, in meters.  The documentation may specify, can't recall.

#### rcallicotte

##### March 01, 2007, 10:51:34 pm #9
Thanks.  It's beginning to make clearer sense.  Out in "deep space" it tends to be sort of challenging to figure out placement, but it must be a mathematical possibility.  Right?

Quote from: Arandil on March 01, 2007, 09:36:46 pm
Quote from: calico on February 28, 2007, 02:41:25 pm
How do the planet Heading, Elevation, and Distance values relate to the Centre coordinates as far as geometry calculations?  I'm no mathematician, so I need it in easy terms, if you can.

I believe you can consider the values to represent the x, y, z offset from 0, 0, 0, in meters.  The documentation may specify, can't recall.
So this is Disney World.  Can we live here?

#### Arandil

##### March 02, 2007, 03:38:41 pm #10
Quote from: calico on March 01, 2007, 10:51:34 pm
Thanks.  It's beginning to make clearer sense.  Out in "deep space" it tends to be sort of challenging to figure out placement, but it must be a mathematical possibility.  Right?

Sure.  What do you want to do?  Set a camera and place a planet in some particular piece of the visual sky there?  Figure out how far a moon/planet COULD be, considering the physics involved?

#### rcallicotte

##### March 02, 2007, 04:00:23 pm #11
I'm working on a program to create an asteroid ring that is somewhat close to realistic.  I'm having trouble loading the TGC, though, and it could be anything.  The basic structure looks sound, but I might be misplacing asteroids or doing something that can't physically be done.

Oshyan, what is the limit on the size of a TGC?  10M or 15M sound feasible?
So this is Disney World.  Can we live here?

#### Oshyan

##### March 04, 2007, 06:09:01 pm #12
Calico, I'm not aware of any specific limit on the size of a .tgc however 10MB sounds well beyond what I would think would be feasible given the slowdowns I've had with larger networks that would have to be much smaller than that. Even a 1MB .tgc would equate to a whole lot of nodes which would be a UI issue if nothing else. So I'm guessing that's where your problem is coming from. Doing asteroids as individual planetoids is probably not the way to go for now...

- Oshyan