MantisBT - VTK
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ID	Project	Category	View Status	Date Submitted	Last Update
0002862	VTK	(No Category)	public	2006-02-08 16:05	2016-08-12 09:54

Reporter	Nick Gnedin
Assigned To	Will Schroeder
Priority	normal	Severity	major	Reproducibility	always
Status	closed	Resolution	moved
Platform		OS		OS Version
Product Version
Target Version		Fixed in Version
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Type

Summary	0002862: Possible loss of precision
Description	I might have discovered a possible bug in VTK. The attached file gives a simple test where squares of decreasing size are placed in front of each other, so that smaller squares are in front of larger ones. Squares are sized by factors of 2, and there are 31 of them, so the smallest one has size of about 1e-9 of the largest one, and cannot be described by single precision coordinates. I use vtkPoints(VTK_DOUBLE) to insure that all coordinates are in double precision. Nevertheless, as you can see by running the test, the artifacts appear when the camera zooms to squares that are about 1e-7 of the largest ones, as if the coordinates are kept in floats despite being requested as doubles. I am not 100% sure it is a bug in VTK, but I did try this test on two different video cards, one NVIDIA (under Linux) and another ATI (under Windows), to reduce a chance that the bug is in the OpenGL implementation. The same behaviour appears under VTK 4.4.2 and 5.0.0.
Steps To Reproduce
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Attached Files	Test.cpp (2,710) 1969-12-31 19:00 https://www.vtk.org/Bug/file/5458/Test.cpp

Issue History
Date Modified	Username	Field	Change
2011-06-16 13:11	Zack Galbreath	Category	=> (No Category)
2016-08-12 09:54	Kitware Robot	Note Added: 0036825
2016-08-12 09:54	Kitware Robot	Status	expired => closed
2016-08-12 09:54	Kitware Robot	Resolution	open => moved

Notes