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straaljager

Creating smooth curve from imported curve geometry

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Hello,

I'm new to Houdini and have searched on the net for answers to my problem, but couldn't find any. I am trying to visualize a brain tractography (white matter fiber tracts) dataset which was exported from Blender as FBX mesh (Blender automatically converts curves to meshes when exporting to FBX). When importing this file into Houdini, it shows up as a ribbon of long quads, which can be reduced to a point line with a polyspline node. Rendering the polyspline directly with Arnold does not nearly look as good as Houdini's native curve primitives (left in the screenshot below). Is it possible to obtain a smooth curve that goes through the points or stays close to them, without resulting in artefacts like the segments in the picture?

 

Tractography mesh exported from Blender

houdini_dti_mesh.thumb.jpg.aa467f5b69a1634b6ab922fadcda0f6a.jpg

The tracts are represented by quad ribbons:

houdini_dti_mesh_close_up.thumb.jpg.acd9cc0e6c072543da2db64f4c43c8cf.jpg

Close-up of one ribbon after polyspline (right) and native curve primitive in Houdini (left):

houdini_curve_test_points.thumb.jpg.a9d60e9890b4d0c2af4d9d2b58ede34d.jpg

Rendering the polyspline with Arnold shows the individual segments:

houdini_curve_test.thumb.jpg.2eb22056178c5ff805b4bc05681b3a1a.jpg

 

Edited by straaljager

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Hey, Welcome to Houdini!

May I suggest using the convert SOP (converting it to third order NURBS)
you may also find it useful to:

  • use the facet SOP using the "Remove Inline Points" toggle and then play with the distance to remove some "oversampling"
  • use the fuse SOP to merge nearby points in corners (to avoid having sharp corners using convert)
  • resample with a large value for "Maximum Segment Length" to reduce the noise in your samples

Or alternatively, you can also keep your geometry at polygons with the resample SOP, setting the "Treat Polygon As" dropdown to "Subdivision Curves"

image.png.0466c3a390e1463b7cf4abbe2c602460.png

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