User manual

© Next Limit Technologies 2010
Maxwell Render 2.5 User Manual
Chapter 18. Appendix V. Glossary | 161
Fresnel Effect: The apparent increase/ decrease of a surface’s reectance based on
viewing angle. The Fresnel effect is dependent on the IOR of the material. The higher the
IOR, the more reective a material becomes at all angles. This means the Fresnel effect
diminishes because the material becomes equally reective at all angles. The effect has
been named after the French physicist who described it.
f-Stop: An important notion in optics, f-Stop expresses the diameter of the diaphragm of
the lens in terms of the effective focal length of the lens. f-Stop is the quantitative measure
of lens speed in photography. The smaller the f-Stop, the bigger the diaphragm opening
(aperture) of the lens is, allowing more light in and making the DOF narrower, meaning
only a small area of the image will be in focus.
GMT: Refers to “Greenwich Mean Time”, generally used as a universal time zone.
IBL: Stands for Image Based Lighting. You can light your scene with a high dynamic
range image (HDR, MXI, EXR). The image used should be in a longitude-latitude
format to work correctly in Maxwell Render. It will be mapped to a virtual sphere that
encompasses your scene. IBL images recreate lighting from real-world light sources to
create realistic lighting environments.
Illuminance: Illuminance is specied in lux, which is dened as one lumen per square
meter. It is a useful setting in Maxwell Render if you want to increase/ decrease the size
of an emitter, and have it emit more or less light with the changed size of the emitter. For
example, if an amount of light is emitted over a larger area, it will give the impression that
the light is weaker.
IOR (complex/full): IOR stands for “Index Of Refraction” and is a measure of how
much the speed of light is reduced as it passes from a vacuum into a material. Complex
or full IOR data are collected from precise measurements in laboratories and describe the
optical properties of a material to the highest degree of accuracy. These materials are
extremely realistic.
ISO: Film ISO, or lm speed, is the measure of a photographic lm’s sensitivity to light.
The lower the ISO, the lower the lm’s sensitivity, requiring a longer exposure, while a lm
with a high ISO needs only a short exposure to light.
Lambertian: Lambertian reectance means that light falling on a surface is scattered
in such a way that the apparent brightness of the surface is the same, regardless of the
observer’s angle of view. In other words: the surface’s luminance is the same regardless
of angle of view. Many rough surfaces, such as unnished wood, exhibit Lambertian
reectance. In Maxwell Render, Lambertian behavior is seen when Roughness is set to
100.
Latitude: Describes a location north or south of the equator. Technically, it is an angular
measurement in degrees ranging from 0 degrees at the equator, to 90 degrees at the
poles. Latitude can be combined with longitude to give a precise position on the Earth’s
surface.
Longitude: Describes a location east or west of a north-south line called the Prime
Meridian. Longitude is given as an angular measurement ranging from 0 degrees at the
Prime Meridian to +180 degrees eastward and -180 degrees westward. Longitude and
latitude together can point to a specic location on the Earth’s surface.
Lumens: Lumens (lm) is the SI unit for luminous ux. It is a common way to specify how
much light is emitted. Light manufacturers usually supply this data.
Luminous intensity: Luminous intensity is the power of light emitted in a certain
direction, and it is specied in candela (cd).
Maxwell.exe: Previously known as MXCL, it is the core rendering application. Whether
you launch your render via the plug-in from your 3D platform or from Studio, Maxwell.
exe is the application that performs the actual rendering. Maxwell.exe also provides tools
for image editing, Multilight controls, scripting features, etc.
Motion blur: The apparent streaking of rapidly moving objects in a still image or a
sequence of images such as a movie. When a camera creates an image, that image does
not represent a single instant of time, but a series of instants over a period of time. As
objects in a scene move, an image of that scene must represent an integration of all
positions of those objects, over the period of exposure determined by the shutter speed
(or shutter angle in the case of an animation). In such an image, an object moving with
respect to the camera will look blurred or smeared along the direction of the relative
motion.
Multilight: Multilight™ is a special feature of Maxwell Render that allows the user to
change intensities of individual lights in the scene during and after the rendering process.
This feature is the rst of its kind in a commercial render engine and it is extremely