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#409 Crash when rendering a blobby near of camera plane

Jose M. Espadero


I am rendering an animation that makes use of Blobby and found several cases that makes aqsis to crash.
The cash seem to happen when a blobby cross the plane of the camera, at a early stage of render,
Blobbies that are near of the camera but does not cross the plane will do aqsis to hang without rendering anything after several hours, even for a very simple scene.
So, my test case is a Blobby segment that goes from -1.0 to 1.0 in the Z axis, and have a radius 0.5, so the blobby surface will extend from -1.5 to 1.5.

When the camera is far (0,0,5) the blobby is rendered correctly
Moving the camera to (0,0,2), near of the blobby, will increase the render time, but sill works.
Moving the camera to (0,0,1.5), even near of the surface. Will hang aqsis.
Moving the camera in a way that its plane cuts the blobby will drop a "Floating point exception". This happens at (0,0,1.4) , (0,0,1) and even at (0, 30, 1), Moving the camera in the Z range 1.5 ..-1.5 will end always with a crash

I attach the example with camera at (0,0,1), which will crash aqsis. Please, move the camera to points given in the report to see the behavior at these points.



  • I forgot to say that I tested it on 1.6.0 version, both in linux and windows. With the same result.

  • Chris Foster
    Chris Foster

    Looking at the blobby code, the blobby bounding box is clipped to the near clipping plane. However, the example RIB file doesn't set any clipping planes, and the default near clipping is only epsilon away from the camera!

    This implies a humongous size of the blobby bounding box in screen space, and a huge grid to do the implicit surface calculations on.

    An easy workaround should be to use the Clipping command, for example, to set the near clipping plane to a z distance of 1, and the far plane to 1000:

    Clipping 1 1000

    To avoid the crash in the code, we should probably impose some limits on the size of the grid used for the blobby calculation...



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