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<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=227450814-04022004>Hi
John,</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=227450814-04022004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=227450814-04022004>Just a
guess, but in OpenGL specifications, the behaviour is undefined when
drawing concave polygons. OpenGL says that all polygons must be convex and if
you want to draw concave shapes, you must tessellate
youself.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=227450814-04022004>But I
don't know how this is handled in VTK.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=227450814-04022004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=227450814-04022004>Hope
it helps,</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=227450814-04022004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=227450814-04022004>--
Julien</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=227450814-04022004></SPAN></FONT> </DIV><FONT face=Tahoma>
<DIV><BR><FONT size=2><SPAN class=227450814-04022004> </SPAN>-----Message
d'origine-----<BR><B>De :</B> John Platt
[mailto:jcplatt@lineone.net]<BR><B>Envoyé :</B> mercredi 4 février 2004
15:00<BR><B>À :</B> vtkusers@vtk.org<BR><B>Objet :</B> [vtkusers]
Concaved Polygon edge shown straight<BR><BR></DIV></FONT></FONT>
<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px">
<DIV class=Section1>
<P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-GB
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Hi users,</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-GB
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-GB
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">I have a single, plane,
curvilinear quadrilateral with 2 straight sides, 1 concaved side and 1
convexed side. This is defined using 6 points and VTK_POLYGON. This is the
only cell in vtkUnstructuredGrid which is input to
vtkDataSetMapper.</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-GB
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-GB
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">The concaved edge is displayed
straight while all other edges are shown correctly. If the polygon is rotated,
evidence of the correct shape can be seen at certain
orientations.</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-GB
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-GB
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">What am I missing? I have attached
the cpp file used with vtk 4.5.0.</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-GB
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-GB
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Many thanks.</SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-GB
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face=Arial size=2><SPAN lang=EN-GB
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">John Platt</SPAN></FONT></P>
<P class=MsoPlainText><FONT face=Arial size=2><SPAN lang=EN-GB
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">#include "stdafx.h"</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">#include "vtkPoints.h" </SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">#include "vtkIdList.h"</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">#include "vtkCellType.h"</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">#include "vtkUnstructuredGrid.h"</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">#include "vtkDataSetMapper.h"</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">#include "vtkActor.h"</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">#include "vtkProperty.h"</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">#include
"vtkRenderWindowInteractor.h"</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">#include "vtkRenderWindow.h"</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">#include "vtkRenderer.h"</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">int APIENTRY WinMain(HINSTANCE
hInstance,</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
HINSTANCE hPrevInstance,</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
LPSTR lpCmdLine,</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
int nCmdShow)</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">{</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> // Define points.</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> vtkPoints* globalCoords =
vtkPoints::New();</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
globalCoords->Initialize();</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
globalCoords->InsertNextPoint( 0, 0, 0 );</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
globalCoords->InsertNextPoint( 1, 0.5, 0 ); // concave</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
globalCoords->InsertNextPoint( 2, 0, 0 );</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
globalCoords->InsertNextPoint( 2, 2, 0 );</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
globalCoords->InsertNextPoint( 1, 2.5, 0 ); // convexed</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
globalCoords->InsertNextPoint( 0, 2, 0 );</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> // Define the polygon
topology.</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> vtkIdList* topology =
vtkIdList::New();</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> for ( int nPts = 0; nPts < 6; nPts++
)</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> topology->InsertNextId(
nPts );</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> // Add the points and the single cell to
an unstructired grid.</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> vtkUnstructuredGrid* UGrid =
vtkUnstructuredGrid::New();</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> UGrid->SetPoints( globalCoords
);</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> UGrid->InsertNextCell( VTK_POLYGON,
topology );</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> // Convert the cell to graphic
primitives.</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> vtkDataSetMapper* faceMapper =
vtkDataSetMapper::New();</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> faceMapper->SetInput( UGrid
);</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
faceMapper->ScalarVisibilityOff();</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> // Create an actor to represent the cell
faces.</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> vtkActor* faceActor =
vtkActor::New();</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> faceActor->SetMapper( faceMapper
);</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> faceActor->GetProperty()->SetColor(
1, 0, 0 );</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> // Create the Renderer, RenderWindow, and
RenderWindowInteractor.</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> vtkRenderer* renderer =
vtkRenderer::New();</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> renderer->AddActor( faceActor
);</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> vtkRenderWindow* renderWin =
vtkRenderWindow::New();</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> renderWin->AddRenderer( renderer
);</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> vtkRenderWindowInteractor* interactor =
vtkRenderWindowInteractor::New();</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> interactor->SetRenderWindow( renderWin
);</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
interactor->Initialize();</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> renderWin->Render();</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> // Main message
loop:</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> MSG
msg;</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> while
(GetMessage(&msg, NULL, 0, 0)) </SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> {</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
TranslateMessage(&msg);</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">
DispatchMessage(&msg);</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> }</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> </SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"> return 0;</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt">}</SPAN></FONT></P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"></SPAN></FONT> </P>
<P class=MsoPlainText><FONT face="Courier New" size=2><SPAN
style="FONT-SIZE: 10pt"></SPAN></FONT> </P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN lang=EN-GB
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT> </P></DIV></BLOCKQUOTE></BODY></HTML>