vtk bug: core dump in vtk{2.4,vtk-nightly} vtkRenderInteractor

[Michael Halle]

A core dump happens on X/OpenGL platforms using an
XRenderWindowInteractor if the RenderWindow's Render() method
isn't called before the interactor is Start()ed.  

My platform:

Sun Ultra, Solaris 2.6, Creator3D graphics, Workshop C++ .

Example:

Compile and run graphics/examplesCxx/Mace .  It works.  Now comment
out the "renWin->Render();" line.  Recompile and run.  Mace dumps
core.

The problem also shows up in the python examples by default, since at
least mace.py doesn't have that line.  The core dump happens when you
first interactor with the window (pretend you were rotating the mace).

What happens:

At least in the nightly release, the core dump happens when the
RotateCamera InteractorStyleTrackball accesses CurrentLight, which is
NULL.  It's null because Render() never had a chance to set up the
default light, using UpdateLights(); the interactor code assumes there
is at least one light.

The 2.4 code probably makes the same assumption, just in a different
part of the code.  

(I tracked the problem down while debugging the python bindings, so
I'm not positive exactly the same problem happens at exactly the same
place in the C++ code.  I'd guess it does, though.)


Michael Halle
mhalle at media.mit.edu


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