7.2. Surface Versus Volume Rendering

In computing at least, “rendering” means “drawing”, and “visualisation” is the process of drawing a picture of data, so the terms “rendering” and “visualisation” are fairly interchangeable.

First, lets look at the two main types of rendering:

7.2.1. Surface Rendering

In this video, we see:

  • Contouring, drawing round objects of interest, labelling pixels, resulting in a segmented region.

  • Converting segmented regions into triangle meshes.

  • Reducing the numbers of triangles, to ensure rendering is fast enough.

  • Rendering such a surface, as a solid surface or as wireframe.

7.2.2. Volume Rendering

In this video, we see how volume rendering is different to surface rendering:

  • Volume rendering works on voxel data directly.

  • There is no explicit segmentation step.

  • The value of a pixel in the image is determined by what a ray of light travels through, and functions that map 3D image (e.g. MR/CT) intensity or gradient to opacity and colour.

7.2.3. Mixed Surface and Volume Rendering

You can also mix surface rendering and volume rendering: