Volume rendering Guide, Meaning , Facts, Information and Description
Volume rendering is a technique used to display a 2D projection of a 3D discretely sampled data set.A typical 3D data set is a group of 2D slice images acquired by a CT or MRI scanner. Usually these are acquired in a regular pattern (e.g., one slice every millimeter) and usually have a regular number of image pixels in a regular pattern. This is an example of a regular volumetric grid, with each volume element, or voxel represented by a single value that is obtained by sampling the immediate area surrounding the voxel.
To render a 2D projection of the 3D data set, one first needs to define a camera in space relative to the volume. Also, one needs to define the opacity and color of every voxel. This is usually defined using an RGBA (for red, green, blue, alpha) transfer function that defines the RGBA value for every possible voxel value.
The simplest way to project the image is to cast rays through the volume using ray casting.
In this technique, a ray is generated for each desired image pixel. Using a simple camera model,
the ray starts at the center of the projection of the camera (usually the eye point) and
passes through the image pixel on the imaginary image plane floating in front of the camera
but before the volume to be rendered. The ray is clipped by the boundaries of the volume to save
time then the ray is sampled at regular intervals throughout the volume. The data is interpolated
at each sample point, the transfer function applied to form an RGBA sample, the sample is
composited onto the accumulated RGBA of the ray, and the process repeated until
the ray exits the volume. The RGBA color is converted to an RGB color and deposited in the
corresponding image pixel. The process is repeated for every pixel on the screen to form the
completed image.
This is an Article on Volume rendering. Page Contains Information, Facts Details or Explanation Guide About Volume rendering