First Steps with Light++

First Steps towards a Light C++ Main program

To create an image, you need (as in real life):

• A Scene, which contains all objects of interest and light sources shining on them (if there are no self illuminating objects)

• A Camera, which contains the viewing information, i.e. the observer position and the exposure time (also provides an automatic exposure time sensitometer).

• A Frame of the Camera, which contains information on how to render the image (quality, raytracing mode) and the `film', i.e. the image device; the film may be a graphics file (currently Targa [preferred] and Jpeg supported) or a graphics window (very rudimentary support)

• A Lens, which defines how the scenery is seen by the camera. A standard lens may be used for wideangle views and small angle view down to telescopic view angles, until the numerical resolution limit is reached. Additional, a fisheye lens is provided by the library. It may be used to create round view images of 180° view angle (which is no possible with the standard lens) and even with view angles of 360° and more - which is not possible with real cameras and lenses. Moreover, images created by the fisheye lens may be used later as Material maps for other images using the inverse fisheye projection.

The Scene

Constructing a Scene is simple:

Scene	World;

This defines a Scene object called World. Class Scene is defined in 3D/Scene.hpp, don't forget to include this header file.

You may now add objects and light sources to the scene.

The Objects

Any object has to be given a Material. The Material must therefore be defined before an object can be defined:

The Material

Construction of a Material is quite a complex thing, since the Material parameters determine the sort of material, like plastic, metal, glass, air, clouds, and even more. At this stage, only the simplest case will be explained, the case of a non-transparent plastic medium. For simplicity, this kind of material is predefined and reuse is easy, the mere required parameter is the Material color:

Material	Red ( rgb_real(1,0,0) );

This defines a Material object called Red, the color for diffuse reflection is set to (red=1.0, green=0.0, blue=0.0). The rest of the Material parameters are taken from the Material structure pointed to by Material*Materials_default, which is initialized at program start with some plastic material.

Class Material is defined in <3D/Material.hpp>, don't forget to include this header file.

Object definition

Now back to the objects. There are many kinds of objects, the definitions of objects in the Light C++ library may be found in 3D/objects/. The simplest object is the Sphere, defined in <3D/objects/Sphere.hpp>, it requires a Material structure, the center point and the radius of the sphere:

Sphere	Centralsphere( Red, vector3(0,0,0), 0.1 );

The newly defined object may now be added to the Scene:

	World.add(Centralsphere);

Hereby the object is made part of the Scene.

The Light Sources

To see the objects, we need some light. Various basic light sources are predefined in <3D/Lights.hpp>, e.g. a light source at infinite distance, shining in the given color from the given direction:

InfiniteLight	Lsinf( rgb_real(1.,1.,1.), vector3(0,0,1));

This makes a white light source at infinite distance shining from above downwards. To make the light source part of the Scene, it has to be switched on within the World object:

	Lsinf.On(World);

Light sources and objects may only be part of one scene. If there exists more than one scene and a light source or an object is added to one scene, it will be deleted from a previous scene.

The Camera

Construction the camera requires the position of the observer and the view point:

vector3	Observer(1,-1,0);
vector3	Viewpoint(0,0,0);

Camera  Kamera(Observer, Viewpoint);

The Camera provides some more properties, which are not explained here.

The Camera's Frame

A Camera's Frame may be constructed by a predefined way of command line arguments:

main(int argc,const char*argv[])
{
	...
Camera::Frame	  frame(argc,argv);

	...
}

The Lens

The Standard Lens

The Fisheye Lens

The User Lenses

How to construct your own lens?

Rendering

The Program

include <3D/Scene.hpp>
include <3D/Material.hpp>
include <3D/objects/Sphere.hpp>
include <3D/Lights.hpp>
include <3D/Camera.hpp>

main(int argc,const char*argv[])
{
Scene	World;

Material	Red ( rgb_real(1,0,0) );

Sphere	Centralsphere( Red, vector3(0,0,0), 0.1 );
	World.add(Centralsphere);

InfiniteLight	Lsinf( rgb_real(1.,1.,1.), vector3(0,0,1));
	Lsinf.On(World);

vector3	Observer(1,-1,0);
vector3	Viewpoint(0,0,0);

Camera  Kamera(Observer, Viewpoint);
Camera::Frame	  frame(argc,argv);
Standardobjektiv  Stdlens(40);

	Kamera.use(Stdlens);
	Kamera.expose(World,frame);

	return 0;
}

Program invocation

main 300x300 main.jpg