| Re: Object Graphics: multiple Views of same model [message #28562 is a reply to message #28561] |
Tue, 18 December 2001 08:11   |
Martin Downing
Messages: 136
Registered: September 1998
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Senior Member |
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David Fanning wrote:
>
> I didn't mean to insult you the other day, Martin.
> I know perfectly well you know what you are doing with
> 3D graphics,
> but sometimes I like to overemphasize the
> point for our readers. :-)
Hi David,
Thats alright, no insult taken!
>
> If I wanted to see two or more views of the same
> polygon object, I think I would start by create
> two or more polygon objects that all shared the
> same data (with the SHARE_DATA keyword). Each
> object could go into its own model, each model
> into its own view, and the views could be
> collected into a scene, that I would display
> in my window.
The key for this application is that we want to set up fixed views in world
coordinates and then move the object model around relative to that, ie
linked transforms. Your method and explicitly ensuring linked model
transforms is the only way to do it that I can think of though. Just tried
it for 3 views and it certainly works. I am disappointed though that the way
RSI has implemented IDL graphics objects does not allow this type of
graphics tree, but there you go!
So currently I have 2 views, both as graphics roots. I cant for the life of
me work out what the purpose of Scenes or Viewgroups are!
>
> This scheme allows you to manipulate the models
> independently to get two or more views of the
> same polygon dataset.
>
> I have to admit, I've never had occasion to
> use the shared data trick, but it seems to me
> the application you describe is exactly why
> it is there.
>
I tried
obj2 = OBJ_NEW('IDLgrPolygon', SHARE_DATA = obj1, col=[255,0,0])
but the connectivity and normals were junk, so I have just repeated
generation of the object.
thanks,
Martin
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