Question

I have a program that prints the cube and which can be rotated. Here’s the code.

public partial class ProjectorForm : Form
{
    Projector projector;
    Cube cube;
    float deltaRot;           



    public ProjectorForm()
    {            
        InitializeComponent();

    }

    private void ProjectorForm_Load(object sender, EventArgs e)
    {

        deltaRot = 0.01f;

        projector = new Projector();
        cube = new Cube(Vector3.UnitZ * 20*10, 10*10, 10*10, 15*10);

        updateTimer.Start();
    }

    private void updateTimer_Tick(object sender, EventArgs e)
    {
        if (rotXBox.Checked)
            cube.RotateX(deltaRot);
        if (rotYBox.Checked)
            cube.RotateY(deltaRot);
        if (rotZBox.Checked)
            cube.RotateZ(deltaRot);



        doubleBufferedPanel1.Invalidate();
    }



    private void doubleBufferedPanel1_Paint(object sender, PaintEventArgs e)
    {

        e.Graphics.Clear(Color.White);
        cube.Draw(projector, Color.Black, doubleBufferedPanel1.ClientSize.Width, doubleBufferedPanel1.ClientSize.Height, e.Graphics);


    }

    private void button1_Click(object sender, EventArgs e)
    {
        deltaRot = float.Parse(deltaRotBox.Text);
    }




}

class Projector
{
    public Vector3 cameraPosition;
    public float planeDistance;
    ProjectorForm n = new ProjectorForm();





    public Projector()
    {
        cameraPosition = Vector3.Zero;
        planeDistance = 256; //Here, multiply by 2 and the scaled cube, how to make that scale when you press the button.

    }

    public PointF Project(Vector3 point, float width, float height)
    {
        float x = cameraPosition.X + ((cameraPosition.Z + planeDistance) / (point.Z - cameraPosition.Z)) * (point.X - cameraPosition.X) + width / 2;
        float y = cameraPosition.Y + ((cameraPosition.Z + planeDistance) / (point.Z - cameraPosition.Z)) * (point.Y - cameraPosition.Y) + height / 2;
        return new PointF(x, y);
    }

    public void DrawLine(Color color, Vector3 p1, Vector3 p2, float width, float height, Graphics g)
    {
        g.DrawLine(new Pen(color), Project(p1, width, height), Project(p2, width, height));
    }

    public void FillPolygon(Color color, Vector3[] vertices, float width, float height, Graphics g)
    {
        PointF[] points = new PointF[vertices.Length];
        for (int i = 0; i < points.Length; i++)
            points[i] = Project(vertices[i], width, height);
        g.FillPolygon(new SolidBrush(color), points);
    }
}

How to make a cube can be scaled by pressing a button. I found the variable planeDistance in the class Projector, when it increased by 2 times the cube is scaled, but I do not know how it can be increased by means of a button.

Answer 1

The field planeDistance is public, so you can change it from outside the class. i.e. just add something like the following to the event handler of a button:

projector.planeDistance += 10; // Change 10 as appropriate

It’s worth noting that this doesn’t change the size of the cube, it changes how far away the camera is from it. So, while the cube appears to be changing in size, that’s just because the camera is moving closer / further away.

---

To actually change the size of the cube you would have to change fields in the cube class.
Since the size is defined by the vectors created in the constructor you don’t really have an easy way of changing them once the cube is created.

1. You could create a new cube whenever you want to change the size (keep track of the size in another variable on the form).
2. You could add a method to the cube class that creates new vectors that define the new size (it would look a bit like the constructor, only populating the arrays, not creating them).
3. You could add a size field to your cube, always create a unit cube (1, 1, 1) then when rendering multiply each vector by your size.