VRML Script Tutorial
VRML Interactive Tutorial
Let there be Light
Materials with Colored Lights
VRML File Structure
Drawing: Shape node
Hierarchical Node Structures
Defining and Instancing Nodes
Defining Levels of Detail
Events in VRML
Let the Music Play
Adding Realism to the world
Information about your world
Definition for Auxiliary Nodes
If you're new to lighting in VRML, there is a Lighting
section in this tutorial which discusses general features of lighting in
VRML. In here only the aspects which are particular to Spot Lights are
Spot Lights define a light source in a specified location pointed
at a particular direction. The light rays from this type of light
are constrained to the interior of a cone, the cone's apex coinciding with
the light's location. The following figure attempts to define a
Point Light graphically (the point where the light rays start is the light
The cone of light is defined by two fields: cutOffAngle and beamWidth.
The cutOffAngle defines the angle of the cone, in radians. The beamWidth
defines the angle of an inner cone within which the light intensity is
constant. The light rays which fall between the inner cone and the outer
cone have a decreasing intensity from the inner to the outer cone. If the
beamWidth is larger than the cutOffAngle then the light has a constant
intensity within the cone.
A Spot light lits all nodes regardless of their position in the file, i.e.
this light is not scoped. There is however a way of limiting the volume
which is lit by this light, one can specify a radius which defines
the maximum distance that the light rays can travel. Objects which are
further away from the light source than the radius, or lie outside
the outer cone are not lit by the light source.
There is still another way to control the attenuation. Using the
attenuation field one can specify how the light grows dimmer with distance,
within the sphere defined by the radius.
The following fields are present in this node:
on specifies if the light is active. This is a boolean field.
intensity has values between 0.0 and 1.0. Higher values specify
ambientIntensity specifies how much this light contributes to
the overall lighting .Values must be between 0.0 and 1.0
color is a RGB field to specify the color of the light.
location which specifies a vector in 3D defining the coordinates
of the light in your world.
direction which specifies a vector in 3D defining the aim of
attenuation is a 3D vector that specifies how the light looses
its intensity as distance from the light source increases. All vector values
must be greater than or equal to zero
radius specifies the maximum distance for the light rays to
travel. Must be greater than or equal to zero.
cutOffAngle specifies the cone within which the light rays are
constrained. Must be greater than or equal to zero, and less than or equal
to 180 degrees, approximately 1.57 radians.
beamWidth specifies an inner cone within which the light rays
have a uniform intensity . Must be greater than or equal to zero, and less
than or equal to 180 degrees, approximately 1.57 radians.
color 1 1 1
location 0 0 0
direction 0 0 0
attenuation 1 0 0
Note: Due to the default location and direction of the Spot
Light the initially loaded world is black. On the VRML world presented
as example the sphere is placed
at -2.5 0 0, the cone is placed
at the origin, and the cylinder
is placed at 2.5 0 0. If you're not familiar with placing shapes other
than at the origin see the Transform