Celestia Forums

I would appreciate basic drawing methods in Celx programming; Are they already implemented in Lua and available in Celx?

to begin with:
1-sort of markPoint(position,style,layer)
which permit to mark any 'point' in space as we already do with celestia objects
2-sort of drawLine(from,to,style,layer)
which could permit basic schetches superimposed over the Celestia scene, for educational purpose.(and for debugging too)
3-the use of layer item is the idea of an object fully dedicated to these 'abstract' sketches, who could be switched easily on/off over the 'natural' scene.

and later on:
4- sort of drawSphere(...),drawCircle(...), drawEllipse(...).
5- theses primitives could be used to define more elaborated methods like drawPolyLine(...),drawPlane(...),drawArc(...)

But first of all, are points 1- and 2- already available in any way?
Thanks
JPierre

Hi JPierre,

All graphic capabilities in Celestia are provided by the OpenGL library. To my knowledge, no drawing functions have been created for Celestia scripting in either language (Cel or Celx).

Until script drawing routines are available, you might consider creating appropriate 3D model files that display lines and points in Celestia.

If you're primarily interested in objects in the solar system, you could define the models as Nebulas in DSC files. They can be turned on and off by enabling and disabling the drawing of galaxies.

If you need to use them while viewing deep space objects, 3D objects can be created that are visible only from one side. To make them visible or invisible, you could use somewhat different viewpoints.

I hope these suggestions for workarounds help a little.

selden wrote:Until script drawing routines are available, you might consider creating appropriate 3D model files that display lines and points in Celestia.
If you're primarily interested in objects in the solar system, you could define the models as Nebulas in DSC files. They can be turned on and off by enabling and disabling the drawing of galaxies.

Thank for your workaround suggestions... of course it's better than nil !
But what I'll need is to define and draw 'abstract objects' , not 'real' ones with fixed geometry:
I mean I'll need lines, polygones and planes whose 'sommets' (extremities?) will be:
1) frame-dependant
2) time object-dependant
Let's imagin for exemple, That I would like to draw a representation of a time dependant plane wich is orthogonal to the line Earth-Sol, and tangent to the Earth surface, at any moment of the Year...
1>? Could it be done with the DSC files implementation???
2>? Anyway, could you give me some reference site on DSC file tehnology?
Thanks alot.
Jpierre

Jean-Pierre,

Unfortunately, objects defined in a DSC (Deep Space Catalog) are fixed in space relative to Celestia's "Universal" coordinate system. They don't move and don't have Beginning and Ending directives.

A plane which stays tangent to the Earth and orthogonal to the Earth-Sol vector would have to be defined in a SSC file (Solar System Catalog).

It would have to be defined as an object orbiting around the Earth, I think. Beginning and Ending directives could be used to make it visible and invisible.

Both SSC and STC descriptions can be found at http://members.fortunecity.com/guilpain/

I have some crude notes about the contents of DSC files at http://www.lns.cornell.edu/~seb/celestia/celestia_notes.html#11.0

Some examples of DSC file usage can be found at http://www.lns.cornell.edu/~seb/celestia/billboard.html

Does this help?