MantisBT - VTK
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ID	Project	Category	View Status	Date Submitted	Last Update
0001158	VTK	(No Category)	public	2004-09-13 11:12	2013-04-05 19:56

Reporter	ovi
Assigned To	Lisa Avila
Priority	urgent	Severity	major	Reproducibility	always
Status	closed	Resolution	fixed
Platform		OS		OS Version
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Target Version		Fixed in Version
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Summary	0001158: vtkFloorFuncMacro produces incorrect results on i386
Description	In file Rendering/vtkVolumeRayCastMapper.h there is a function named vtkFloorFuncMacro. This function does not produce correct results for all inputs on a platform that does not use the "quick-and-dirty" solution: inline int vtkFloorFuncMacro(double x) { #if defined i386 \|\| defined _M_IX86 double tempval; // use 52-bit precision of IEEE double to round (x - 0.25) to // the nearest multiple of 0.5, according to prevailing rounding // mode which is IEEE round-to-nearest,even tempval = (x - 0.25) + 3377699720527872.0; // (2*51)1.5 // extract mantissa, use shift to divide by 2 and hence get rid // of the bit that gets messed up because the FPU uses // round-to-nearest,even mode instead of round-to-nearest,+infinity return ((int*)&tempval)[0] >> 1; #else // quick-and-dirty, assumes x >= 0 return (int)(x); #endif } As an example take vtkFloorFuncMacro(0.99989) which should return 0. Instead it returns 1, which is wrong. Because of failures like this, volume rendering that uses vtkVolumeRayCastMapper can produce random crashes. After I replaced the body of this function with the standard "floor(x)" all the random crashes I experienced before are gone.
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Issue History
Date Modified	Username	Field	Change
2011-06-16 13:11	Zack Galbreath	Category	=> (No Category)
2013-04-05 19:56	Berk Geveci	Status	customer review => closed

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