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Maxwell Render 2.5 User Manual

Chapter 18. Appendix V. Glossary | 160

Attenuation distance: Attenuation is the reduction in amplitude and intensity of a signal.

As light travels through a material, it loses energy. The Attenuation distance parameter

in Maxwell Render allows you to specify how far light can move through an object before

losing half its energy. For example, if you have a 2 cm thick glass window, and you set the

Attenuation distance to 2 cm, the light shining through the glass on the other side will be

half as bright.

BSDF: BSDF, or Bidirectional Scattering Distribution Function, is a set of mathematical

functions that describe how light interacts with a material. These functions can describe

opaque, transparent and translucent materials and their surface properties such as

roughness, color etc.

Burn: An image is burned when its contrast is raised too much, and it results in the image

containing uniform blobs of color, black, or white where there actually should be detail.

In Maxwell Render, Burn is a tone-mapping parameter that controls how fast the image

is over-exposed.

Camera Frustum: Generally, the eld of view of the camera. The Camera Frustum in

Maxwell Render is indicated by a yellow frame. Anything inside this frame will be rendered.

Channels: Rendering information can be stored separately in different images or

channels, and this is usually done for compositing purposes. Maxwell Render can split

the information obtained during the rendering process and produce independent Shadow

channels, Alpha channels, Material Id channels, Object Id channels, Z-buffer channels,

Motion Vector channels, Diffuse channels, and Reection channel, as well as the

complete composed image.

Clip map: A texture with completely black or completely white pixels only. It can be

used in Maxwell Render as a Layer weight to determine which parts of a material should

be made visible (white areas) or invisible (black areas).

Depth of Field: Depth of Field, or DOF, is the area in front and beyond the camera

focal distance (the camera target) where the objects will appear in focus. The camera

parameters that affect the DOF the most are the f-Stop and focal length settings. Other

variables such as lm width/ height and distance of the camera to the subject will also

affect the DOF.

Diaphragm: In photography, a diaphragm is a thin opaque structure with an opening

(aperture) at its center. The role of the diaphragm is to stop the passage of light, except

for the light passing through the aperture. The diaphragm is placed in the light path of a

lens or objective, and the size of the aperture regulates the amount of light that passes

through the lens. Its diameter is controlled by the f-Stop parameter. The smaller the f-Stop

value, the bigger the diaphragm opening, and viceversa.

Diffraction: This is an effect that happens when light goes through small holes, causing

interference patterns. All lenses exhibit diffraction, especially when the camera lens is

pointing straight at a strong light source such as the sun. Diffraction is also known as

glare.

Diffuse: The reection of light from an uneven or granular surface, resulting in an

incoming light wave being reected at a number of angles. Diffuse reection is the

opposite of specular reection. It is the difference between glossy (specular) and matte

(diffuse) paints.

Dispersion: The effect seen when a beam of light passes through a prism and is split up

into different wavelengths of light.

Efcacy: Refers to the amount of light produced by a light source, usually measured in

lumens. Efcacy species how many lumens are emitted per watt and thus how efciently

electricity is converted into visible light.

Emitter: In Maxwell Render, “emitter” refers to geometry that has an emitter material

applied to it.

Focal length: The focal length of a lens refers to the distance between the lens itself

and its focal point (where the light will be focused, usually where the lm is). The focal

length of a lens determines the eld of view (FOV), or how much you see of your scene,

and also the DOF. A small focal length lens (15-24mm) is said to be a wide-angle lens

because it captures a lot of the scene (it has a wide FOV), and its DOF is wide (almost

all the objects in the scene will be in focus). A large focal length lens (80-200mm) is said

to be a telephoto lens as it acts like a binocular, “zooming” in to a particular area of your

scene (it has a small FOV) and the DOF will be very narrow (only a small portion of your

scene will be in focus).

FPS: An abbreviation for “frames per second”.

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