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List:       flightgear-users
Subject:    Re: [Flightgear-users] Aircraft creation tutorial
From:       Wunder.Hans-Georg () t-online ! de (Hans-Georg Wunder)
Date:       2004-08-19 17:28:54
Message-ID: 4124E356.3010502 () t-online ! de
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Frederic Bouvier wrote:
> Hans-Georg Wunder wrote:
> 
> 
>>High all,
>>
>>since version 0.7.2 I played around with flightgear. Now I am writing a
>>little tutorial with pictures, how to create an aircraft.
>>Many things I am able to understand , but some things are mysterious. I
>>searched for informations in the mailing lists and howtos,
>>I analysed existing models, but I can't understand it. Here are my
>>questions:
>>
>>    - How can I add a light to a model (for example a green nav light)?
>>
>>
>>    - How can I add a light to an object in the scenery (for example
>>       a red light at the top of a tower) ?
> 
> 
> Lights are simulated in OpenGL by a material color that is not affected
> by ambient or diffuse light source. This way it can be see at night when
> there is no light source. This color is called 'emissive' or 'emission'
> for that purpose. In an AC3D aircraft or building or whatever models,
> the first lines describe material properties like this :
> 
> MATERIAL "AerialLight" rgb 1 1 1 amb 1 1 1 emis 1 1 1 spec 1 1 1 shi 72
> trans 0
> 
> note the keyword 'emis' follow by three '1' to say that 'AerialLight' is
> emitting white. ( beware, it is not a light source, so it has no effect
> on the surrounding, it is just plain white every time ).
> 
> Now, this material color must affected to a graphical object. Either a
> point, a billboarded quad or a solid. Ground light and airport lights are
> points. Radio tower lights are billboards that are growing with the distance
> from the viewer. Bay bridge lights are solids. Why ? because it appears that
> the OpenGL fog is fading lights to early to achieve the proper effect,
> so there are several strategies. For ground light, an alternate fog density
> is computed and set and the lights are drawn after the terrain.
> For 3d models, it is not (yet) possible to modify the fog on the fly so
> the size of the light objects is modified with the distance from the viewer.
> 
> So, to reply precisely to your question, you can add a light to a model
> by editing it with your 3d modeler, add an object that has the shape of
> your light, give it an emissive material color, and eventually, add
> a 'dist-scale' and/or a 'billboard' kind of animation to the animation
> xml file. If you want the light to blink, you can add a 'timed' animation
> to alternatively show two objects that have the same shape but with
> two different material color, one with emissive, the other without.
> 
> Regards,
> -Fred
> 

Thank you for your information. Now my aircraft has navigation lights.
But how is it possible to create a light with effect on the surrounding 
? For exsample a landing light ??
And how it is possible to illuminate a 2D-Panel ?

Kind regards

Hans-Georg





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