Opened 17 months ago

Last modified 17 months ago

#1226 new defect

aliasing problem in 2D q rotation?

Reported by: pkienzle Owned by:
Priority: major Milestone: sasmodels 1.0
Component: SasView Keywords:
Cc: Work Package: Plotting/Graphing Enhancements

Description

Consider the following image: there appears to be an aliasing problem depending on quadrant.

Created using:

 sascomp ellipsoid -2d -nq=128 theta=60 phi=45 -pars -midq radius_polar=250 theta_pd=5 -double!

The problem persists in single precision running on the GPU and long double precision running on the CPU.  It is still there for -nq=127. It is less visible for -nq=256.   It does not appear to be a plotting issue.

Attachments (1)

ellipsoid-2d.png (50.8 KB) - added by pkienzle 17 months ago.

Download all attachments as: .zip

Change History (5)

Changed 17 months ago by pkienzle

comment:1 Changed 17 months ago by pkienzle


comment:2 Changed 17 months ago by pkienzle

It is not the model, and not the jitter:

sascomp parallelepiped -2d -nq=128 theta=60 phi=45 -pars -lowq

comment:3 Changed 17 months ago by pkienzle

  • Priority changed from major to minor

Okay, not a modelling issue. The problem comes from the rebinning algorithm in the plotter, which takes arbitrary qx,qy,I data and puts it into a regular mesh. The code is in sasmodels.data._build_matrix, which was copied and modified from sas.sasgui.plottools.PlotPanel.

This should still be fixed, but it is a minor problem.

comment:4 Changed 17 months ago by butler

  • Component changed from sasmodels to SasView
  • Priority changed from minor to major
  • Work Package changed from SasModels Redesign to Plotting/Graphing Enhancements
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