[jitter] rtt,ctt and fbo example file crashes max 5

the file jit.gl.slab-float-readback.maxpat, found in the jitter 1.7
examples/render/slab folder causes max to crash.  there isn't a render
destination in the patch.  what confuses me is that when i place a
destination (a jit.window or pwindow) in the patch it still crashes.  can
someone tell me why?


i'm intrigued to get a better understanding of the rtt fbo and ctt readback
mechanisms, but am not convinced that this patch will provide the answers.
can someone explain how these operate in jitter together with the advantages
of each, or point me to somewhere that has a succinct explanation?


as i understand these mechanisms:

a) copy to texture (ctt), is a basic gl operation that copies the back
buffer and and uses it to replace the previous texture that was rendered.

b) render to texture (rtt) bypasses the buffer and renders directly to a
texture.

c) the frame buffer object (fbo) has textures rendered to it before calling
the rtt step, and this operation speeds up the overall rendering of a scene.


presumably when a message is sent to jitter to use the fbo the set up for
the object is injected into the rendering process.  But, if this operation
speeds up rendering why not use it all the time in place of other the other
options?  why does it need an explicit instruction? or are there occasions
when using a fbo is pointless, eg when not using depth testing?


thanks


pelado


i'm on a mac powerbook, ATI radeon 9700, using OSX 10.4.11
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