[C] give the earth some light

Antecedents feed

• WPF 3D preliminary
• Use the keyboard to control the camera angle of view
• Use the mouse to control the camera angle of view
• Make a for your second dimensional wives 3D Gallery
• use C# Rub an earth

Despite the creation of an earth , But I always feel something wrong , The key is that the light is given too evenly , From east to West , All parts of the earth have the same brightness , It's obviously unreasonable .

The reason for this problem , Because the light effect we have been using is AmbientLight, The characteristic of this lighting effect is to uniformly illuminate all objects . To make the Earth spin more real , Maybe a point light source is better , After all, the sun is a point .

Results after using point light , The effect is as follows

The code is easy to modify , That is, when the coordinate is $(5,-2,5)$ An all white light source is placed in the position of .

private void DefineLights(Model3DGroup group)
{
    
    var ptLight = new PointLight(Color.FromRgb(255,255,255), new Point3D(5, -2, 5));
    group.Children.Add(ptLight);
}

Of course , The sun is very far from the earth , To make the effect look more realistic , Or pull the point light further , For example, put it on $(50,-3,50)$ The location of ; Or don't point the light at all , Direct the last line light source . The effects of both are as follows

among , The definition method of linear light source is , among Vector3D Represents the direction of light .

private void DefineLights(Model3DGroup group)
{
    
    var white = Color.FromRgb(255, 255, 255);
    var dirLight = new DirectionalLight(white, new Vector3D(-50, 4, -50));
    group.Children.Add(dirLight);
}

Although line lights look more realistic , But it's not cool , If you call, the stage seems better .SpotLight Conical light effect , The effect is

The code is

private void DefineLights(Model3DGroup group)
{
    
    var white = Color.FromRgb(255, 255, 255);
    var spLight = new SpotLight(white, new Point3D(10, 10, 10),
        new Vector3D(-10, -10, -10), 10, 5);
    group.Children.Add(spLight);
}

among ,SpotLight On initialization , The input variables represent the position of the light source 、 Irradiation direction 、 Outer divergence angle and inner divergence angle .