[vtk-developers] Multiple sets of texture coordinates with OpenGL2 backend

Ken Martin ken.martin at kitware.com
Wed Dec 20 08:53:56 EST 2017


Have you tried?

  /**
   * Select a data array from the point/cell data
   * and map it to a generic vertex attribute.
   * vertexAttributeName is the name of the vertex attribute.
   * dataArrayName is the name of the data array.
   * fieldAssociation indicates when the data array is a point data array or
   * cell data array (vtkDataObject::FIELD_ASSOCIATION_POINTS or
   * (vtkDataObject::FIELD_ASSOCIATION_CELLS).
   * componentno indicates which component from the data array must be
passed as
   * the attribute. If -1, then all components are passed.
   */
  virtual void MapDataArrayToVertexAttribute(
    const char* vertexAttributeName,
    const char* dataArrayName, int fieldAssociation, int componentno = -1);


You will need to do something with that attribute in the shader code. I
believe only point association is supported.  All textures will
automatically get bound in order with names starting with texture_0 and
going up.



On Tue, Dec 19, 2017 at 11:32 PM, Simon Drouin <drouin.simon at gmail.com>
wrote:

> Is there any way to have multiple sets of texture coordinates on a
> vtkPolyData with the OpenGL2 backend?
>
> In the legacy OpenGL backend, it used to be possible to have multiple sets
> of texture coordinates on a vtkPolyData by adding multiple arrays, each
> containing a set of texture coordinates, to the point data of the polydata,
> by doing something like this:
>
> polyData->GetPointData()->AddArray( tcoordArray )
>
> And then associating the array to one of the textures with:
>
> polyDataMapper->MapDataArrayToMultiTextureAttribute( textureUnit,
> arrayName );
>
> This behavior is not implemented in the OpenGL2 backend. The mapper
> considers only the array returned by polyData->GetPointData()->GetTCoord()
> as texture coordinates and uses it for all textures. Initially, I thought I
> could do the job by modifying the shader program used to render the
> polydata, but the mapper doesn't seem to pack the extra arrays from the
> point data into the VBO, so the data is not there for the shader.
>
> Any solution?
>
> Thanks in advance.
>
> s.
>
>
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-- 
Ken Martin PhD
Distinguished Engineer
Kitware Inc.
28 Corporate Drive
Clifton Park NY 12065

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