[ REQ 5836]: how can I set the "ADD" instead of "REPLACE" mode in my external module?

[han at iris.usc.edu]

Hi,

I am writing some external modules, and I want to add the second geom
to the camera, instead of repacing the previous one. How can I control 
this mode? 

Thanks,

Song
USC
Los Angeles

PS: Currently, when I write out the second geom, the previous one will 
disappear. If I write our 100 geom, I can only see the last one, with 
all 99 previous geoms gone. I want all 100 geoms stay there on the screen.