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Re: [Nel] 3DSMax question : lightmaps parameters

From: Cyril 'Hulud' Corvazier
Subject: Re: [Nel] 3DSMax question : lightmaps parameters
Date: Wed, 11 Sep 2002 11:10:13 +0200

Hi Mr Phlam! :-)

> As far as I understand, here is the simplest process to get lightmaps on 
> a mesh in the Object Viewer :

> . Assign a NeL material to the mesh and set its Shader type to 
> 'LightMap', select a lightmap texture channel 2.

Yes. You can use any mapping channel.

> . Assign an UVW map modifier to the mesh, with the following parameters 
> : Box mapping,  mapping channel #2

You can map your UVW2 channel like you want (using any mapping plugin) 
to avoid wrapping artifacts.

> . Create a light (omni or spotlight), set its Color, Multiplier, Cast 
> shadow, Far Attenuation ('start' value / 'end' value / 'use' checkbox)

Yes, the light must have its far attenuation activated to be used by the 
lighting system.
If you want shadows, check cast shadows.

> . Check the Utilities / NeL Export / Options : 'Export lighting' and 
> 'Shadow' checkboxes

Yes, this global options allow you to disable the lighting system to get a 
quick preview in the viewer.
Manual export form NeLExport are affected by this options too.

Build_gamedata exports are not affected by this option but by the quality 
option in the file build_gamedata/cfg/site.cfg.
Build_gamedata has 2 quality mode : DRAFT and FINAL.
In FINAL mode, lightmaps are generated.
In DRAFT mode, lightmaps are not generated. 

> . If you select the mesh(es) and push Utilities / NeL Export / View the 
> Scene, you should get a nice rendering in the Object Viewer.

You got it.

> . How can I have soft shadows ? All I can get is sharp raytraced-like 
> shadows, even if the 'Light method' parameter is set to 'Soft Shadow' in 
> the Options

Soft shadows are implemented only for directionnal lights. It's working.

> . The NeL material(s) that has/have the 'Lightmap' shader type must have 
> a Diffuse bitmap (NeL Textures rollout) or the lightmaps won't be calculated

Yes, for the moment, the material must have a diffuse bitmap to use lightmap.
It could be done without but it doesn't work today.

>   . Does the soft shadow radius work ?
>   . What does 'Soft shadow cone length' mean ?
> For a light

Yes, it is used by directionnal light when soft shadow is activated.
Soft shadow are a modified raytracing algorithm.
It not clip ray, but 3d cone. The lumel intensity is proportionnal to
the non-clipped cone area. Shadow radius and shadow length are
the parameters of this clipped cone.

>   . what is the difference between 'Realtime light' and 'Realtime Sun 
> light' ?

Ok, this affect the dynamic lighting system. The flag 'Realtime light' tells to
the export system that this light is a dynamic light, ie, can light objects 
at runtime. 'Realtime Sun  light' tells to the export system that this light
is a Sun light and must be modulate by the current scene sun color.

Dynamic light informations are stored in the .zone files for 
landscape and in .ig files for interiors.

Objects (like people, weapons, ie, non-lighmapped objects) placed
in the NeL engine can be affected by the dynamic lighting system.

For the moment, there is no dynamic shadows, but it should coming
in the next monthes.

>   . what is the difference between 'Realtime light' and 'Animated 
> dynamic light' ?

>   . what is the meaning of the Lightmap Name ? Changing it doesn't 
> change the generated lightmap filename

No, but a lightmap will be generated for each lightmap name.

If you have 2 lights with 2 different lightmap names, your object
will get 2 lightmaps. Then in NeL, you will be able to control
the lightmaps intensity independenlty (by multiply each lightmap with a color) 
at runtime. To find the proper lightmap, you will use its lightmap name.

For exemple, you can put 2 light groups in your scenes, some with
name "day" and some with the name "night". In your client, you will be
able to activate day or night by multipling the proper lightmaps
with Black or White color.

Thanks for asking good questions ! :-)

Cyril Corvazier.

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