Signal 15 and Lighting

[Knobi der Rechnerschrat]

Hallo everybody,

  we have seen the 'killed by signal 15' problem several times on a 70/GT
running 3.1D. It can usually be tracked down to a severe corruption of the
Matrix stack (doing 500 pushmatrix calls without popmatrix and vice versa).
I can understand that the window system gets problems in this cases, but
probably an error message at user level would be more appropriate than
'flatening' the graphics systems.

  Tim Hall wrote something about a lighting problem he has. We see a similar
problem. We have an application with two light sources positioned roughly at
the z-axis at +/- infinity. The whole application runs in MVIEWING mode, and
I'm loading identity matrices hen it is neccessary. Usually we have coordinates
that fit into ortho(-30.,30.,-30.,30.,-30.,30.). For one reason we change the
ortho to 'screen coordinates' using ortho2(0,(float)XMAXSCREEN,
  0.,(float)YMAXSCREEN). When resetting the ortho to our 'normal' values, the
light sources have changed from z-direction to x-direction and the shading
appears to be some kind of 'dirty'. The ortho change is accompanied by a
mode change to and from OVERDRAW mode. Unfortunatelly the sequence in question
is called from several places, but the error occurs only on half of the
occasions. I know this description is not sufficient to describe the problem
fully, but perhaps somebody has a hint.

Regards
Martin Knoblauch

TH-Darmstadt
Physical Chemistry 1
Petersenstrasse 20
D-6100 Darmstadt, FRG

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