Light Map Options

 

Ambient:   The ambient color in lighting calculation.
Background: The back color of lightmap image, not related to lighting calculation.
Image Width, Image Height: The lightmap image resolution.
Sample spacing:   The Patch Size of surfaces namely.
Lightmap Number:  When the number is 0,the lightmap image number is determined by Sample spaceing and Image Width & Height; When the number is >0,the program will rectify the Patch Size of surfaces in order to limit the lightmap image number.
Texture Format: Changes light map texture format.
Cast shadow: Specifies whether to take into account shadows in ray tracing lighting calculation.
Mirror Lighting: Specifies whether take into account mirrors in ray tracing lighting calculation.
Enable Channel Filter: Specifies whether enable Lighting Channels in ray tracing lighting calculation.
Save float data: Specifies whether to save the float lighting data to disk file. Disabling this function will economize on disk space and the time of saving/loading scene file, but the Expose command function (in 'Post process') will become unusable if you do choose the no-float-lighting-data-saving setting. 
Brightness rectification:  Adjust the lightmap images brightness. It's image process only.
Blur: Specifies blurring of the bitmap image. It's a simple antialiasing method.
Expose: Control the lighting data conversion from FLOAT to BYTE. The formula for the conversion is float data  X  Expose Value.
Exposure coefficient:  Control the Exposure of radiosity lighting calculation
Render resolution: The render resolution of the radiosity solution. More resolution yields more detail, but of course far more render time too.
Curtness Mode: The Curtness Mode of radiosity can save a lot of computer time but it's imprecise.
AO Range: The detection distance for Ambient Occlusion calculating, less is fast.
Double Side Rendering: Also render back face for all mesh when do radiosity calculating, this can reduce lighting leak.