Page 21/36 position of the light to the maximum distance the light slowly diminishes. This is called light attenuation. Lights do not cast shadows. If you have a sphere in front of the plane there will be no shadow on the plane, the light rays will seem to pass through the sphere without any interference. You have to use other techniques to obtain shadows. Lightmaps, Z-shadows or shadow volumes for instance. There are three types of lights: 1.  Omni light  – this is a light located in one point radiating light rays equally to all directions. You can thing of omni light as of an electric bulb hanging on a cable freely in the air. 2.  Spot light – spot light shines a beam or a cone of light in one direction. You can change the width or angle of the cone. A 360º cone would become an omni light. Example of spot light is a torch light. 3.  Parallel light – uniform mass of parallel light rays with same direction shining from a plane in infinite distance form a parallel light. You can change position of parallel light but it has no effect whatsoever. Parallel light is usually used to simulate sunshine. TGLDummyCube GLScene also has helper objects. Helper object is an invisible object that is used for organizing other objects in groups, to show distances, directions and positions in space. You should learn how to use dummy cube as much as possible because it can simplify a lot of things. Dummy cube can be used to store objects as its children. If you want to for example move all of the objects just move the dummy cube. If you want to delete the objects just call DeleteChildren function of the dummy cube. Dummy cube can simplify rotations. You can create joints with dummy cubes where each dummy cube will have restricted rotation only in one axis. You can make dummy cube visible run time with  VisibleAtRuntime  property. Dummy cube is represented by cube outlined with dotted lines. Basic geometry Basic geometry objects are simple objects with hard coded geometry. The geometry can be described with mathematical formulas. You can change individual parameters of the object but the basic shape will always stay the same. TGLSprite Sprite is a 2D image mapped on a plane that always faces the camera. Unlike HUD sprite TGLSprite is placed in 3D world and can be moved closer or further from the camera. If the sprite gets too close to the camera it can create unwanted visual errors. A transparent texture is usually used with sprites. The image can turn around its center by changing Rotation property. TGLPoints You can create array of points or just one point with this object. Points are dots in space. They have Size parameter which determines how many pixels in diameter the point will have on screen. If the point has size 3 it will be represented by 3 pixels on screen whether the point may be close to the camera or far away from the camera. Perspective does not apply here. Points can be rounded or squared and antialiased. GLScene beginner's guide, Jan Zizka, 2005