[vtkusers] [Fwd: Re: Using OpenGl with VTK]

[Utkarsh Ayachit]

Please keep the questions to the mailing list, so that others can
benefit/contribute as well.

To add New():
* take a look at any concrete class in VTK eg. vtkCollection (the New is
  declared in the header and defined using
vtkStandardNewMacro(vtkCollection); in the cxx.

* not using the viewport in the RenderOpaqueGeometry should not be a
problem. It's only provided if needed.

Utkarsh




Mohammed Amine SAHTARI wrote:
> Thank you very much Utkarsh.
> 
> I am tring to implement your solution but I have some problems.
> 
> 1) I create vtkMyDerivedProp.h and vtkMyDerivedProp.cxx
> 
>  I subclass vtkProp :
>        - I copy the class code of vtkProp3D (.h and .c files)
>        - I replace all the words :
>                vtkProp3D /by/ /vtkMyDerivedProp /and Prop3D by 
> /MyDerivedProp/
>        - I include /"vtkGl.h"/ in vtkMyDerivedProp.h
>        - I add RenderOpaqueGeometry() in vtkMyDerivedProp.h like this :
>                /virtual int RenderOpaqueGeometry(vtkViewPort* )
>                {/
> 
> /             glBegin (GL_LINES);
> 
>              glVertex2f (-2.5, 2.5);
> 
>              glVertex2f (2.5, -2.5);
> 
> 
>              glEnd ();/
> 
> /               }/
> 
> 2) In my program :  
> 
>  - I include and instantiate vtkMyDerivedProp :
> 
>     /  //# include "vtkMyDerivedProp.h"
>       vtkMyDerivedProp *MyDerivedProp;/
> 
> -         I use  vtkMyDerivedProp :
> 
> /     vtkRenderer  *renderer = vtkRenderer  ::New();/
> 
> /      vtkMyDerivedProp-> RenderOpaqueGeometry(renderer);/
> 
> /      renderer->AddProp(vtkMyDerivedProp);/
> 
> 
> *Problem *: vtkMyDerivedProp is used without been defined!
> 
> *Question 1 :* How can I define it ?   (vtkMyDerivedProp::New()  doesn't 
> work)
> 
> *Question 2 :*  RenderOpaqueGeometry has vtkViewPort* in input but 
> doesn't use it. Is it a problem ?
> 
> How can I fix this?
> 
> Looking forward to hear from you soon,
> 
> Amine**
> 
> 
> 
> 
>  
> 
> 
> 2008/8/14 Utkarsh Ayachit <utkarsh.ayachit at kitware.com 
> <mailto:utkarsh.ayachit at kitware.com>>
> 
>     iren->Start() results in repeated calls to renWin->Render() on
>     interaction. This will clear whatever you had drawn. A better
>     approach is to subclass vtkProp(or one of it's subclasses) and put
>     your rendering code in RenderOpaqueGeometry() /
>     RenderTranslucentPolygonalGeometry()/ RenderOverlay() etc. depending
>     upon what pass you want it to be rendered and then add the prop to
>     the renderer. That way every time the renderer re-renders, your code
>     will be executed.
> 
> 
>     Utkarsh
> 
>     Mohammed Amine SAHTARI wrote:
> 
> 
>         I want to add an OpenGl code in an application of VTK.
> 
>         For this purpose, I try to draw lines using commands OpenGL.:
> 
>         *1) I add this on the top of the program :*
> 
>         #include <GL/gl.h>
>         *2) I place my OpenGL commands after renWin->Render() but before
>         iren->Start()** :  *
> 
> 
>         renWin->Render();
> 
>            glBegin (GL_LINES);
>               glVertex2f (-2.5, 2.5);
>               glVertex2f (2.5, -2.5);
>             glEnd ();
> 
>         iren->Start();
> 
> 
>         *But it doesn't appears.*
> 
>         did I miss something ? How can I do this work ?
>         Looking forward to hear from you soon,
> 
>         Amine
> 
> 
> 
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