[vtkusers] Drawing a single triangle

[flymolo at gmail.com]

After updating the positions, call Grid->Modified(), that should keep it in  
sync.

On Jan 11, 2009 2:03pm, Kerry Loux <louxkr at gmail.com> wrote:
> Gerrick,
>
> Thanks for the response. I'm using C++, and created this method to create  
a triangle object:
>
> // Create the objects
> Points = vtkPoints::New();
> Array = vtkFloatArray::New();
> Triangle = vtkTriangle::New();
>
> Grid = vtkUnstructuredGrid::New();
> TriangleMapper = vtkDataSetMapper::New();
> aTriangle = vtkActor::New();
>
> // Triangles have three points
> Points->SetNumberOfPoints(3);
>
> // Add some dummy points to the vtkPoints object
>
> Points->InsertPoint(0, 0.0, 0.0, 0.0);
> Points->InsertPoint(1, 0.0, 0.0, 0.0);
> Points->InsertPoint(2, 0.0, 0.0, 0.0);
>
> // Set up the float array
> Array->SetNumberOfComponents(3);
>
> Array->SetNumberOfTuples(3);
> Array->InsertTuple3(0, 1, 1, 1);
> Array->InsertTuple3(1, 2, 2, 2);
> Array->InsertTuple3(2, 3, 3, 3);
>
> // Set up the triangle object
> Triangle->GetPointIds()->SetId(0, 0);
>
> Triangle->GetPointIds()->SetId(1, 1);
> Triangle->GetPointIds()->SetId(2, 2);
>
> // Set up the unstructured grid object
> Grid->Allocate(1, 1);
> Grid->InsertNextCell(Triangle->GetCellType(), Triangle->GetPointIds());
>
> Grid->SetPoints(Points);
> Grid->GetPointData()->SetTCoords(Array);
>
> // Set up the mapper
> TriangleMapper->SetInput(Grid);
>
> // Set up the Actor
> aTriangle->SetMapper(TriangleMapper);
>
>
> aTriangle->GetProperty()->SetColor(1.0, 1.0, 0.0);// Yellow
>
> // Add it to the scene
> Renderer->GetRenderer()->AddActor(aTriangle);
>
> After I create the triangle, I call an update method that does this:
>
>
> Points->SetPoint(0, Node1.X, Node1.Y, Node1.Z);
> Points->SetPoint(1, Node2.X, Node2.Y, Node2.Z);
> Points->SetPoint(2, Node3.X, Node3.Y, Node3.Z);
>
> // Re-render the scene
> Renderer->GetRenderer()->Render();
>
>
> The first time I call this update function, the triangle is displayed  
correctly. Subsequent calls, however, do not update the position of the  
triangle. I tried changing the update method to include most of the  
procedure for creating the object, but I still get no change in the  
object's position. Is there something I can do to update the position of  
the triangle after it has been created? Do you know why my update function  
works the first time but has no effect after the first time it is called?
>
>
> Thanks for your help!
>
> -Kerry
>
> On Wed, Jan 7, 2009 at 9:31 PM, Gerrick Bivins  
gbivins at objectreservoir.com> wrote:
>
>
>
>
>
>
> You have to create a data set (vtkPolyData) and add the triangle as a  
cell and the points are specified as well.
>
> Look hear for an example:
>
>  
http://public.kitware.com/cgi-bin/viewcvs.cgi/*checkout*/Examples/DataManipulation/Python/BuildUGrid.py?root=VTK&content-type=text/plain
>
>
>
>
> Gerrick
>
>
>
>
> On 1/7/09 8:18 PM, "Kerry Loux" louxkr at gmail.com> wrote:
>
>
>
>
>
>
> Hello,
>
>
>
> For my application, I need to display a single triangle in 3-space. The  
triangle is not necessarily equilateral. What is the easiest way to create  
a triangle object? I considered vtkTriangle and vtkTriangleStrip, but I'm  
not clear on how to assign the locations of the vertices. Also, as far as I  
can tell the vtkTriangle (and vtkCell) classes don't have any kind of  
GetOutput() function. How do you map these classes to an actor? I was  
hoping for some kind of primitive shape source, similar to vtkCyliderSource  
or vtkSphereSource, but there doesn't seem to be any.
>
>
>
>
> I'm still using the 5.0.4 release.
>
>
>
> Thanks for your advice!
>
>
>
> -Kerry
>
>
>
>
>
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