Direct Vs Indirect Methods

Volume Visualization | | Iso Surfaces

Direct vs. Indirect Volume Visualization Methods:

Direct Method: Direct Volume Rendering is the reversal of the scanning process: It used the stack of images to produces a virtual X-Ray image for a particular point of view.

Indirect Method: An iso surface is the set of points ot the data set that have the same iso value. The point set forms a closed surface, which can be extracted and represented by a triangle mesh. This procedure is called iso surface extraction.

DVR absorption rendering (left), isosurface extraction by Marching Cubes Algorithm (right):

Angio-VR vs. Angio-IsoSurface

Advantages of DVR:

  • Interactive display of the entire data set.

Disadvantage of DVR:

  • Requires hi-end graphics hardware.

Advantages of iso surfaces:

  • Occlusion of hidden surfaces.
  • Triangle mesh can be shaded.

Disadvantages of iso surfaces:

  • Not the entire data visible, only parts with a respective iso value.
  • Mesh extraction is not interactive.

Volume Visualization | | Iso Surfaces