Beam tracing

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Beam tracing

Beam tracing is a derivative of the ray tracing

Ray tracing

In computer graphics, ray tracing is a technique for generating an digital image by tracing the path of light through pixel in an . The technique is capable of producing a very high degree of photorealism; usually higher than that of typical scanline rendering methods, but at a greater computation time....
algorithm

Algorithm

In mathematics, computing, linguistics and related subjects, an algorithm is a sequence of finite instructions, often used for calculation and data processing....
that replaces rays, which have no thickness, with beams. Beams are shaped like unbounded pyramids, with (possibly complex

Complex polygon

The term complex polygon can mean two different things:*In computer graphics, as a polygon which is neither convex polygon nor concave polygon.*In geometry, as a polygon in the unitary space plane, which has two complex number dimensions....
) polygon

Polygon

In geometry a polygon is traditionally a plane Shape that is bounded by a closed curve path or circuit, composed of a finite sequence of straight line segments ....
al cross sections. Beam tracing was first proposed by Paul Heckbert and Pat Hanrahan

Pat Hanrahan

Pat Hanrahan is a computer graphics researcher, the Canon USA Professor of Computer Science and Electrical Engineering in the Computer Graphics Laboratory at Stanford University....
.

In beam tracing, a pyramidal beam is initially cast through the entire viewing frustum

Viewing frustum

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Encyclopedia

Beam tracing is a derivative of the ray tracing

Ray tracing

Algorithm

Complex polygon

Polygon

Pat Hanrahan

Viewing frustum

In 3D computer graphics, the viewing frustum or view frustum is the region of space in the modeled world that may appear on the screen; it is the field of view of the notional camera....
. This initial viewing beam is intersected with each polygon in the environment, from nearest to farthest. Each polygon that intersects with the beam must be visible, and is removed from the shape of the beam and added to a render queue. When a beam intersects with a reflective or refractive polygon, a new beam is created in a similar fashion to ray-tracing.

A variant of beam tracing casts a pyramidal beam through each pixel

Pixel

In digital imaging, a pixel is the smallest item of information in an image. Pixels are normally arranged in a 2-dimensional grid, and are often represented using dots, squares, or rectangles....
of the image plane

Image plane

In 3D computer graphics, the image plane is that Plane in the world which is identified with the plane of the monitor. If one makes the analogy of taking a photograph to rendering a 3D image, the surface of the film is the image plane....
. This is then split up into sub-beams based on its intersection with scene geometry. Reflection

Reflection (physics)

Reflection is the change in direction of a wavefront at an wiktionary:interface between two differentmedium so that the wavefront returns into the medium from which it originated....
and transmission (refraction

Refraction

Refraction is the change in direction of a wave due to a change in its speed. This is most commonly observed when a wave passes from one optical medium to another....
) rays are also replaced by beams. This sort of implementation is rarely used, as the geometric processes involved are much more complex and therefore expensive than simply casting more rays through the pixel.

Beam tracing solves certain problems related to sampling and aliasing

Aliasing

In statistics, signal processing, computer graphics and related disciplines, aliasing refers to an effect that causes different continuous signals to become indistinguishable when sampling ....
, which can plague conventional ray tracing. However, the additional computational complexity that beams create has made them unpopular. In recent years, increases in computer speed have made Monte Carlo

Monte Carlo method

Monte Carlo methods are a class of computational algorithms that rely on repeated random sampling to compute their results. Monte Carlo methods are often used when computer simulation physics and mathematics systems....
algorithms like distributed ray tracing

Distributed ray tracing

Distributed ray tracing, also called distribution ray tracing and stochastic ray tracing, is a refinement of ray tracing that allows for the rendering of "soft" phenomena....
much more viable than beam tracing.

However, beam tracing has had a renaissance in the field of acoustic modelling, in which beams are used as an efficient way to track deep reflections from sound source to receiver (or vice-versa), a field where ray tracing is notoriously prone to sampling errors.

Beam tracing is related in concept to cone tracing

Cone tracing

Cone tracing is a derivative of the ray tracing algorithm that replaces rays, which have no thickness, with cones. Cone tracing is related to beam tracing, but uses circular rather than polygonal cross sections....
.

Beam tracing

See also