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currently work is done on support for multiple windows.


+ each gemwindow represents a window - specifically an on-screen window or an output (ieee1394, file, ?)

+ there should be objects to output to other resssources (e.g. pbuffer,...) - offscreen rendering shouldn't have to worry about framerates, because it's assumed they are used every rendercycle

+ rendering is controlled by gemcontrol

+ it should be possible to attach gemheads to certain "rendering contexts", e.g. to render a gemlist only to a specific window - offscreen windows probably need to be treated differently, because there can be multiple offscreen windows rendered in the same pass; but we still want to be able to associate more than one gem chain to an offscreen...probably we should associate onscreen windows by a name/symbol, and offscreens by a range of rendering priorities (ie. gemhead 46-52 go to offscreen 1, but 53-55 got to offscreen 2, then offscreen 1 and 2 are rendered to [gemhead 60 firstscreen]?)

+ RenderTrigger: each gem-object should receive a trigger message once a render-cycle. if several GemOutputs are connected to one gemcontrol, gem-objects will receive the trigger-message only once and not for each GemOutput.

problems and possible solutions:

timing issues

what if several "contexts" run at different speed

solution: just do it: compile each gemhead into a display-list and rebuild it only, if it was modified (what for do we have the setModified()-thingie)

sharing display-lists:

display-lists are server-based and can only be shared on one display/server. it is impossible to share display-lists across several (remote) displays (might only be of interest for linux)

possible solution: (non-invasive!, so we don't need to care)


a big MUST is compatibility with prior versions of Gem.

solution: use gemwindow and gemcontrol to simulate a gemwin

associating gemlists with contexts.

see ContextNames

objects involved:


gemwindow, GemOutput


GemBase (?)

controlling the rendering GemcontrolGemoutput

code that is affected:

obviously: GemOutput, gemwindow

obviously: GemMan, gemcontrol

GemCache: currently rather useless; might get important again, see RenderTrigger

lighting ! (lights used to be allocated globally, this will not work at all for multiple openGL-contexts,...)

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