Maximum Intensity Projection (MIP) is a technique that visualizes only the voxels with the maximum intensity encountered along each ray within volumetric data onto the screen. Huygens current version avoids typical aliasing artifacts and ensures the highest possible MIP rendering quality by combining advanced ray tracing with a unique perfect interpolation technique.

Huygens MIP Renderers optimally support GPU acceleration, which greatly reduces render times. Rendered results are identical between CPU and GPU, and thus enables dynamic switching. Due to the nature of the high quality ray tracing algorithm, rendered MIP images always show a certain amount of perspective. This means that objects farther away from the viewpoint appear smaller and that parallel lines converge.

Image Description:
The Huygens MIP renderer window showing a Paramecium in color mode depth-coding in z. Regions of the image with a lower z value appear blue whereas region with a higher z value appear red. Image courtesy of A. Aubusson-Fleury CNRS, Gif sur Yvette, Paris.

A maximum intensity projection (MIP) is a simple ray-tracing technique where the maximum intensity encountered along each ray is projected onto the screen. Rays are cast from a virtual viewpoint and pass through the object. Along each ray, the maximum intensity is recorded and projected onto a virtual canvas. As you can see in this diagram, objects in the background can be projected through objects in the foreground as long as they have a higher intensity. By doing this, you are always looking at the most significant objects in the sample.




Image Description:
A schematic overview of MIP rendering. The maximum intensities along rays originating in the view point are projected.

Since the 19.10 version of Huygens, the MIP Renderer has two special color modes that do not appear in the other renderers: Depth-coding and Depth-coding Z. In these modes each point is given a hue based on the depth at which the maximum intensity was found. This depth can either be the distance to the viewpoint (in case of Depth-coding , viewing-angle dependent), or simply the true z depth in the sample (in case of Depth-coding Z, not dependent on viewing angle). The hues are automatically spread out over the complete range of depths visible in the current view. By adding a Hue bar, the relation between color and depth is shown. An example of a depth-colored image with a Hue bar can be seen in the image below.

Image Description:
The MIP renderer in color mode depth-coding showing a Paramecium. Regions of the image close to the viewpoint appear blue whereas region far away appear red. Image courtesy of A. Aubusson-Fleury CNRS, Gif sur Yvette, Paris.

Rendering a movie

The Huygens Movie Maker allows you to create sophisticated animations using the MIP, SFP and Surface renderers. However, the MIP renderer can also create simple animations on its own by transitioning between two custom keyframes.

Movie Description:
Animated MIP rendering of an isolated Rat Hepatocyte couplet recorded by Dr. Permsin Marbet at the Department of Anatomy, University of Basel, Switzerland, in the lab of Prof. Lukas Landmann.