Көлемдік деректерді бейнелеудің сәулелік қабаттау әдісі

Image based volume rendering technique
Volume ray casting, sometimes called volumetric ray casting, volumetric ray tracing, or volume ray marching, is an image based volume rendering technique. It computes 2D images from 3D volumetric data sets (3D scalar fields). Volume ray casting, which processes volume data, must not be mistaken with ray casting in the sense used in ray tracing, which processes surface data. In the volumetric variant, the computation doesn't stop at the surface but "pushes through" the object, sampling the object along the ray. Unlike ray tracing, volume ray casting does not spawn secondary rays. Because ray marching does not necessarily require an exact solution to ray intersection and collisions, it is suitable for real time computing for many applications for which ray tracing is unsuitable.

The technique of volume ray casting can be derived directly from the rendering equation. It provides results of very high quality rendering. Volume ray casting is classified as an image based volume rendering technique, as the computation emanates from the output image and not the input volume data, as is the case with object based techniques.

The adaptive sampling strategy dramatically reduces the rendering time for high quality rendering – the higher the quality and/or size of the data set, the more significant the advantage over the regular/even sampling strategy. an intersection point is approximated between the ray and a surface defined by a signed distance function (SDF). The SDF is evaluated for each iteration in order to be able take as large steps as possible without missing any part of the surface. A threshold is used to cancel further iteration when a point has reached that is close enough to the surface. This method is often used for 3D fractal rendering. When rendering screen space effects, such as screen space reflection (SSR) and screen space shadows, rays are traced using G buffers, where depth and surface normal data is stored per each 2D pixel.