LightSource Class Reference

Abstract base class for LightSources. More...

#include <LightSource.h>

Inheritance diagram for LightSource:

Public Member Functions
virtual Colour	getIlluminationAt (const Point &point) const =0
	Determine how much light reaches a Point from this LightSource. More...
virtual double	getDistanceToLight (const Point &point) const =0
	Determine how far away the light source is from a given Point. More...
virtual Direction	getLightDirection (const Point &point) const =0
	Direction from light source to a point. More...

Protected Member Functions
	LightSource (const Colour &colour)
	LightSource constructor. More...
	LightSource (const LightSource &lightSource)
	LightSource copy constructor. More...
virtual	~LightSource ()
	LightSource destructor. More...
LightSource &	operator= (const LightSource &lightSource)
	LightSource assignment operator. More...

Protected Attributes
Colour	colour_
	The Colour of this LightSource's illumination. More...

Detailed Description

Abstract base class for LightSources.

LightSources provide illumination to the scene. All light sources have a Colour, but other properties may vary.

As an abstract base class, you cannot create a LightSource directly. Instead one of its concrete subclasses must be created.

Constructor & Destructor Documentation

LightSource() [1/2]

LightSource::LightSource ( const Colour &  colour )

protected

LightSource constructor.

Parameters

colour

The Colour of this LightSource's illumination.

LightSource() [2/2]

LightSource::LightSource ( const LightSource &  lightSource )

protected

LightSource copy constructor.

Parameters

lightSource

The LightSource to copy.

~LightSource()

LightSource::~LightSource ( )

protectedvirtual

LightSource destructor.

Member Function Documentation

getDistanceToLight()

virtual double LightSource::getDistanceToLight ( const Point &  point ) const

pure virtual

Determine how far away the light source is from a given Point.

This is a bit tricky, to get around the fact that there are several general types of light. There are basically three types we are interested in:

• AmbientLightSource, which does not have a location, and which does not create shadows.
• PointLightSource and SpotLightSource, which have a fixed location, so cast shadows when an object is between the point of interest and the light source's location.
• DirectionalLightSource, which does not have a specific location, and casts shadows if there's anything blocking that direction to the point of interest.

For a PointLightSource or SpotLightSource the direction is well defined. For a DirectionalLightSource we can return infinity. For an AmbientLightSource we can return -1. This is never a valid distance, so can be used to indicate that we can skip the lighting computations for this source.

Returns

The distance to the light source (with special values as above).

See also

getDirectionToLight()

Implemented in PointLightSource, DirectionalLightSource, and AmbientLightSource.

getIlluminationAt()

virtual Colour LightSource::getIlluminationAt ( const Point &  point ) const

pure virtual

Determine how much light reaches a Point from this LightSource.

The amount of light emitted by a LightSource is determined by its colour property, but this generally varies across the Scene. This method returns a scaled value to apply to the colour of the light at a given Point in the Scene.

Parameters

point

The Point at which light is measured.

Returns

The illumination that reaches the Point.

Implemented in PointLightSource, DirectionalLightSource, and AmbientLightSource.

getLightDirection()

virtual Direction LightSource::getLightDirection ( const Point &  point ) const

pure virtual

Direction from light source to a point.

Return a Direction pointing from the given point towards the light source. For most light sources this is well-defined, but for AmbientLightSources it is not. This Direction is used for lighting and shadow calculations, however, so this is not a problem. We can return any value for AmbientLightSource, since it will never be used.

Parameters

point

The point where the ray is being computed.

Returns

The Direction from the point towards the light.

See also

getDistanceToLight()

Implemented in PointLightSource, DirectionalLightSource, and AmbientLightSource.

operator=()

LightSource & LightSource::operator= ( const LightSource &  lightSource )

protected

LightSource assignment operator.

Parameters

lightSource

The LightSource to assign to this.

Returns

A reference to this to allow for chaining of assignment.

Member Data Documentation

colour_

Colour LightSource::colour_

protected

The Colour of this LightSource's illumination.

---

The documentation for this class was generated from the following files:

• LightSource.h
• LightSource.cpp