Strange Performer behaviour combined with glDrawPixels.

Graham Jones (graham.jones++at++sharp.co.uk)
Thu, 05 Sep 1996 18:10:48 +0100

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Here goes ....

The first problem is this.

I have a two pass rendering system where a scene is drawn into a
channel. After that the scene is grabbed as a texture and drawn into a
second window using a stencil mask and mucking about with the colour
mask as well. The stencil is stored as an image which is written to the
channel using glDrawPixels. The texture is drawn onto a simple geoset.

I have having problems drawing the stencil mask into the window. If
texturing is enabled then it seems random as to whether the stencil
image is drawn when I call glDrawPixels in the draw callback for the
channel - I am enabling stenciling and, I think, setting other
appropriate things.

Sometimes the image is drawn and the program behaves correctly,
sometimes it doesn't. So I might be rotating an object, or moving
through a scene and the resulting picture will jump between the
correctly stencilled version and something incorrect, when the stencil
was not written.

However, if I disable textures (the simulation is based on perfly so I
just hit 't') everything works perfectly.

Is this meant to happen (seems strange if it is) or is either me or
Performer doing something wrong? If it's not Performer could someone
point me in a direction I might look to solve this.

Secondly ........

I've created a channel which is only displayed if I use the APPCULLDRAW
process model (all in one process) if I split into separate processes
(any model) the channel is not displayed and it's draw callback is not
called. The callback is being setup, the channel created and viewport
set, but I get no channel. I do get the other two channels I am
creating.

Again, any suggestions?

Graham.
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