[vtkusers] (no subject) - Arrows

[Simon J. Rees]

If you don't want just the line produced by vtkHedgeHog and want a complete arrow you can join a cylinder and cone using vtkAppendPolyData before putting it through vktGlyph3D. You can change the appearance (lines vs surfaces) by adjusting the parameters of the cone and cylinder and setting the representation to wireframe or surface. Setting the cone resolution to 2 just gives two orthogonal triangles that are useful for a simple arrow head. For example:

vtkCylinderSource cyl
    #cyl SetResolution 10 ;# for complex arrows
    cyl SetResolution 1
    cyl SetRadius .02
    cyl SetHeight 2

vtkTransform cylTrans
    cylTrans Identity
    cylTrans RotateZ  90
    cylTrans Translate  0 -1.0 0

vtkTransformPolyDataFilter cylTransFilter
    cylTransFilter SetInput [cyl GetOutput ]
    cylTransFilter SetTransform cylTrans

vtkConeSource cone
    #cone SetResolution 10  ;# for complex arrows
    cone SetResolution 2
vtkTransform coneTrans
    coneTrans Identity
    coneTrans Translate  2.5 0 0
vtkTransformPolyDataFilter coneTransFilter
    coneTransFilter SetInput [cone GetOutput ]
    coneTransFilter SetTransform coneTrans

vtkAppendPolyData arrow
    arrow AddInput [cylTransFilter GetOutput ]
    arrow AddInput [coneTransFilter GetOutput]
    arrow Update
vtkGlyph3D arrows
    arrows SetInput [reader GetOutput]
    arrows SetSource [arrow GetOutput]
    arrows SetScaleFactor $vscale
    arrows SetScaleModeToScaleByVector
vtkLookupTable lut
    lut SetHueRange .667 0.0
    lut Build
vtkPolyDataMapper vecMapper
    vecMapper SetInput [arrows GetOutput]
    vecMapper SetScalarRange $minv $maxv
    vecMapper SetLookupTable lut
vtkActor vecActor
    vecActor SetMapper vecMapper

# for simple arrows
    [vecActor GetProperty] SetRepresentationToWireframe
    [vecActor GetProperty] SetAmbient 1
    [vecActor GetProperty] SetDiffuse 0
    [vecActor GetProperty] SetSpecular 0

# for complex arrows
 #   [vecActor GetProperty] SetRepresentationToSurface
#    [vecActor GetProperty] SetAmbient 0
  #  [vecActor GetProperty] SetDiffuse 1
  #  [vecActor GetProperty] SetSpecular 0

I find that ambient lighting is better for the simple type of arrows. Hope this helps

-sjr

  ----- Original Message ----- 
  From: Simon Bulman 
  To: vtkusers at public.kitware.com 
  Sent: Thursday, April 19, 2001 4:07 AM
  Subject: [vtkusers] (no subject)


  Hi All,

  I want to display vector orientation and magnitude using arrows.
  Is there a way to do this. I looked at the vtkHedgeHog class but this seems to draw lines
  only (no arrow tip). The vtkGlmph2D has an arrow but is of course only for 2D where as my
  data is 3D. The vtkGlmph3D can be used with a cone (for example) but I tried this a it looks
  messy to me (unless you use a high resolution for the cone, but this gets slow!)

  Any ideas??

  Thanks
  Simon

  ================================
  S.D.Bulman.
  Senior Research Officer.
  University of Wales Swansea.

  S.D.Bulman at swansea.ac.uk

  (W) +44 (0)1792 513179
  (H)  +44 (0)1792 511144
  ================================

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