[vtkusers] Where is the math behind world to display coordinates and vice versa, implemented in vtk?

[Allie Vacanti]

VTK uses the standard transformation process used in OpenGL. There are a
few tutorials online that give an overview of this, one that I've found
useful in the past is here:

http://www.songho.ca/opengl/gl_transform.html

As for the VTK-specific implementation, the code that implements this
process is spread out across several locations in vtkOpenGLCamera,
vtkRenderer, and vtkViewport. The class vtkCoordinate provides a convenient
API to convert coordinates between display/world or to any intermediate
coordinate system.

If you're only concerned with world <-> display and are interested in
seeing the math used, a more compact replication of this transformation
logic can be found in the (internal) FastDepthAwareCoordinateConverter
class here:

https://github.com/Kitware/VTK/blob/master/Rendering/Core/vtkBillboardTextActor3D.cxx#L62-L193

HTH,
Allie

On Wed, Jan 31, 2018 at 2:08 AM, vinmean <iamdpak at gmail.com> wrote:

> I want to recreate the transformation from display to world and world to
> display coordinate system.  Where is the math behind coordinate conversion
> implemented? I am unable to trace it from the viewport class that provides
> the member function WorldToDisplay and DisplayToWorld.
>
>         renderer->SetWorldPoint(wrld_cord);
>         renderer->WorldToDisplay();
>         renderer->GetDisplayPoint(scr_cord);
>
> Please point me to the math either in the code or in some tutorials.
>
>
>
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