BeamTest User Manual

A library module from the Persistence of Vision Ray Tracer (POV-Ray) Object Collection.

Abstract

[Demo] Sometimes, it is desirable to know the behavior of light refracting through or reflecting off a transparent or specular object before incorporating the object into a scene. Examples could be a gem cut or a lens system. BeamTest provides for optical testing of such objects by shooting beams of light at two-dimensional slices of objects.

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Overview

Downloaded Files

Key Files
File Description
beamtest.html The user manual (this document)
beamtest.inc The BeamTest software
beamtest.jpg Sample output
beamtest.pov An example scene file
READMEnnnnnn.html Important information that you need to know
Other Files
File Description
beamtest.css A support file for the user manual
beamtest_cc-lgpl.png A support file for the user manual
beamtest_description.txt A brief description of BeamTest
beamtest_keywords.txt A list of keywords
beamtest_prereqs.txt Prerequisites (empty file)
beamtest_thumbnail.png Sample output
cc-LGPL-a.png Administrative support file
Versionnnnnnn.js Administrative support file

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Usage

Include this file once prior to using any of the macros: 

#include "beamtest.inc"

Including the file more than once is harmless, though unnecessary.

A camera is set up automatically.

Light fixtures are arrayed along the left side of the image. The user chooses the height, aiming, and color of the lights.

The objects to be tested should be placed on the right (x > 0), with the slice to be tested along the x-y plane. All tested objects must be declared as a photons { target }; in addition, refractive objects must be declared hollow.

Prerequisites

None.

Name Space Compliance

All file names, global identifiers, and local identifiers comply with the Object Collection revised naming standards. The prefixes for this module are “beamtest” and “beam.”

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Parameters

The following parameters may be modified by declaring them prior to including beamtest.inc.

Parameter Description Default
Beam_extinction Scattering extinction of the environmental media. This value may need to be increased if Beam_image_depth is increased. A practical maximum appears to be 0.1. 0.0
Beam_field_of_view Camera angle, in degrees 15.0
Beam_fixture_length Length of each light fixture, in POV units 0.6
Beam_fixture_radius Radius of each light fixture, in POV units 0.1
Beam_fixture_shadow Whether or not the light fixtures cast shadows. Set this parameter to no if the fixtures interfere with the light beams. yes
Beam_fixture_x Horizontal position of the light fixtures -5.0
Beam_image_depth Depth (in the z-direction) of the environmental media, in POV units. Set a large value if a test object deflects light outside the x-y plane. (Warning: This may slow render times and oversaturate deflected light beams.) Slightly more than twice Beam_radius
Beam_image_width Width of the image, in POV units 32/3
Beam_max_trace Maximum trace level 15
Beam_photons
  • If greater than 1.0, the photon count;
  • Otherwise, if greater than 0.0, the photon spacing;
  • Otherwise photons are not used.
0.005
Beam_photons_media Media photons max steps 200
Beam_radius Radius of each light beam, including the falloff, in POV units 0.05
Beam_umbra The width of the bright core of each light beam, i.e., without the falloff, as a fraction of the total diameter 0.5

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Macros

Beam_angled (Height, Color, Angle)

A light beam with fixture, aimed by angle.

Arguments:

Height:
The height of the fixture, with 0.0 at the middle of the image.
Color:
The color of the light.
Angle:
The angle of the light beam from the horizontal.

Beam_sloped (Height, Color, Slope)

A light beam with fixture, aimed by mathematical slope.

Arguments:

Height:
The height of the fixture, with 0.0 at the middle of the image.
Color:
The color of the light.
Slope:
The slope of the light beam, Δvertical ÷ Δhorizontal.

Beam_targeted (Height, Color, Target)

A light beam with fixture, aimed at a target point.

Arguments:

Height:
The height of the fixture, with 0.0 at the middle of the image.
Color:
The color of the light.
Target:
The target point. If the z-coordinate is non-zero, the result is undefined.

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Other Public Identifiers

Identifier Type Description
Beam_media media The media used for the test environment

Any identifiers not documented in this manual are subject to change or elimination in a future update.

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About BeamTest

© 2008 Richard Callwood III. Some rights reserved. Licensed under the Creative Commons-GNU Lesser General Purpose License.

Change Log

Version Date Notes
n/a November 21, 2007 Software is created.
1.0 July 30, 2008 Software is adapted for the Object Collection.
1.0.1 August 4, 2008 User manual is edited; software is unmodified.
1.1 September 1, 2008 Namespace compliance is extended to local identifiers.

User Manual (this document) updated September 1, 2008.

Acknowledgements

Many thanks to Warp (who will recognize his parabolic mirror) and to Blue Herring.

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