VTK/Geovis vision toolkit

Requirements

There are two parts to the project:

• Video / related meta data rendering and interactions.
• Displaying video / meta data in geospatial context.

As per our discussion we have gathered following requirements for the project.

• Easy to put together.
• Provides 2D and 3D mode where in 2D it will allow quick validation, manipulation abilities.
• Provides the ability to visualize, video, track, and associated ranking.
• Ability to provide input as sequence of images or a video file.
• Provides the ability to manipulate track data. User should be able to insert a new one, modify the existing one.
• Provides the ability to select a region with pixel level accuracy and draw a track on top of it.
• Provides the ability to play many video files (small or large video) files.
• Provides a layout for the videos in space so that each can be seen clearly for a view point.
• Allows the videos to play individually or globally.1
• Provides the ability to toggle different layers of information.
• Provides geo spatial context.

Design

• vtkVideoElementRepresentation would contain all the information layers and make sure that they are in sink.

Also this is the representation thats responsible for consuming the data for each video.

• vtkVisStrategyRepresentation

<source lang="cpp">

// Interface for this class is not as clear as it should be. Basically it transforms all layers // associated with any given vtkVideoElementRepresentation and represents this transformation via // some geometry. class vtkVisStrategyRepresentation : public vtkRenderedRepresentation { public:

 // Return transformation matrix that can be used to offset any other representation. 
 vtkMatrix4x4 GetMatrix(); 

 virtual void PrepareForRendering(vtkRenderView* view); 

};

class vtkVideoElementRepresentation : public vtkRenderedRepresentation { public:

 void AddTrackRepresentation(vtkTrackRepresentation* tr); 
 void AddVideoRepresentation(vtkVideoRepresentation* vr); 
 void SetVisStrategyRepresentation(vtkVisStrategyRepresentation* vsr);

 // Update all the layers and call \c PrepareForRendering(....) on each. 
 virtual void PrepareForRendering(vtkRenderView* view);

private:

Internal* Implementation; };

class vtkTrackRepresentation : public vtkRenderedRepresentation { public:

 virtual void PrepareForRendering(vtkRenderView* view);

}

class vtkVideoRepresentation : public vtkRenderedRepresentation { public:

 void SetScalarProperty(double value, double range[2]);

 // Can have 0 or many scalar representations. 
 void AddScalarRepresentation(ScalarRepMode);

 virtual void PrepareForRendering(vtkRenderView* view);

}

</source>

Geovis

• Dealing with precision issues

When dealing with large numbers (earth radius is 6357000) in rendering causes issues of Jitter. This is a known problem as the GPU uses single precision floats as the data type. There could be couple of ways this issue can be dealt with.

1. On the float change of origin 2. Piecewise change of origin 3. Using FO (floating approach as described in this paper link??. 4. Use lat / lon in radians and height in Km instead of meter.