D3PLOT 22.1

Point Light Sources (Positional & Directional)

Point light sources (positional & directional)

Up to 8 point light sources may be defined, each of which is independently controllable. At the top level of the lighting panel they may be turned on/off and have their intensity set from 0 - 100%. To change any other attributes use the SET... button.

SET... Setting detailed light attributes

The following detailed attributes for each light may be set:

OFF/ON Turns this light on or off.

Brightness Sets the light brightness in the range 0 - 100%. (nb: it is more efficient to turn a light OFF than to use 0% Brightness .)

PRESETS >

Provides some pre-computed positions for lights.

These may not give exactly the locations you want, but they can form a good starting point.

(The default light in D3PLOT, light 1, is positioned at "Right Shoulder".)

Theta/Phi

Spherical Coordinates control for the Vector of the specific light you are currently on.

This lets you experiment with the direction in which that light is facing more easily than selecting a specific vector via the textbox.

Definition Method

Positional or Directional (by vector)

Example of Positional light

A "positional" light is defined by its location in space, and this method is generally used for lights close to the object.

This example shows a dummy with a positional light in its lap. (The light itself has been added artificially here, it would not normally be visible on a plot.)

Because the light is "local" it (correctly) does not illuminate the tops of the arms or the front of the legs.

Positional lighting is slightly more expensive than directional to compute, but is necessary if the true effects of lights close to the object are to be simulated.

Example of Directional light

A "directional" light is defined only by its vector, and assumed to be infinitely distant (like the sun).

This is the same model as above, but now the light is directional, defined by a vector pointing through the previous light source position towards the dummy. (The vector arrow has been added artificially, it would not appear on a plot.)

The differences are clear: the whole of the front of the dummy has been illuminated, as have the surfaces which previously were dark.

This is a little bit cheaper to compute than the positional equivalent, as "local" vectors from facet to light source need not be computed.

Defined lights as Tied to Model and Screen space systems

Light Tied to Model space

<== Before ..transform .. After ==>

When a light is tied to Model space it is transformed along with the object.

Light Tied to Screen space
<== Before ..transform .. After ==>
When a light is tied to Screen space it remains fixed in space as the object is transformed.

(In these examples the light sources have been added artificially to illustrate their positions. They would not appear on an actual plot.)

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