[vtkusers] Texturing a surface triangle - how to?

[Tron Darvann]

Dear VTK-users,

Does anybody know how to accomplish the following:

I have 
1) a triangle defined as 3 points,
2) And I have a texture (a 2D image), and finally I have
3) the texture coordinates for 3 positions in the texture.

How do I paste my triangular patch of the image as a 2D texture
onto my triangle?

The simple example in TPlane_test.tcl pastes a texture onto a
vtkPlaneSource, but in that example the texture coordinates
are created by the vtkPlaneSource.  In my case the texture
coordinates are read from file and inserted e.g. into a 
vtkFloatArray (is that the way to do it?)  [I am aware of the
possibillites for creating texture coordinates through
vtkTextureMapToPlane, vtkTextureMapToSphere and vtkTextureMapToCylinder
and manipulation through vtkTransformTextureCoords, BUT since I
already have my coordinates explicitly defined, I do not need
these classes...]

(Eventually, when I know how to paste texture on a
single triangle, I can go on to texture all the triangles
in a surface scan of an object.)

Thanks for any suggestions.

Tron Darvann


Here some code to get the idea of what I'm trying to do:

# This script (modified from CreateStrip.tcl) 
# shows how to manually create a vtkPolyData with a
# triangle.  Then we paste a texture onto it using 
# three texture coordinates in an image...?

package require vtk
package require vtkinteraction

# First we'll create some points.
#
vtkPoints points
    points InsertPoint 0 0.0 0.0 0.0
    points InsertPoint 1 0.0 1.0 0.0
    points InsertPoint 2 1.0 0.0 0.0
 vtkCellArray strips
    strips InsertNextCell 3;#number of points
    strips InsertCellPoint 0
    strips InsertCellPoint 1
    strips InsertCellPoint 2
 vtkPolyData profile
    profile SetPoints points
    profile SetStrips strips
 vtkPolyDataMapper map
    map SetInput profile

vtkBMPReader bmpReader
  bmpReader SetFileName "C:/tron/projects/3dMD/export/050406092854.bmp"
vtkTexture atext
  atext SetInput [bmpReader GetOutput]
  atext InterpolateOn

vtkActor triangle
    triangle SetMapper map
    triangle SetTexture atext

# Explicitly specify texture coordinates: a triangular patch in the input texture.
vtkFloatArray texcoord
  texcoord SetNumberOfComponents 2
  texcoord SetNumberOfTuples 3
  texcoord SetTuple2 0 0.2348 0.7891
  texcoord SetTuple2 1 0.2454 0.7830
  texcoord SetTuple2 2 0.2128 0.7790

###### HERE MISSING CODE: TO APPLY THE TEXTURE COORDINATES !!!####
    
# Create the usual rendering stuff.
vtkRenderer ren1
vtkRenderWindow renWin
    renWin AddRenderer ren1
vtkRenderWindowInteractor iren
    iren SetRenderWindow renWin

# Add the actors to the renderer, set the background and size
#
ren1 AddActor triangle

ren1 SetBackground 1 1 1
renWin SetSize 250 250
renWin Render

# render the image
#
iren AddObserver UserEvent {wm deiconify .vtkInteract}

# prevent the tk window from showing up then start the event loop
wm withdraw .