private PointF Project(Vector3D v)
{
    float scale = 400 / (v.Z + 300);
    return new PointF(
        ClientSize.Width / 2 + v.X * scale,
        ClientSize.Height / 2 + v.Y * scale
    );
}

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Windows.Forms;

namespace CSharpGraphicsApp
{
    public class Task22_RotatingCube : Form
    {
        private float rotX = 0, rotY = 0, rotZ = 0;
        private readonly Timer timer = new Timer();
        private Vector3D[] cubeVerts = new Vector3D[8];
        private Vector3D[] projected = new Vector3D[8];

        public class Vector3D
        {
            public float X, Y, Z;
            public Vector3D(float x, float y, float z) { X = x; Y = y; Z = z; }
        }

        public Task22_RotatingCube()
        {
            Text = "Задание 22 — Вращающийся 3D-куб (Rotating Cube)";
            Size = new Size(700, 600);
            BackColor = Color.Black;
            DoubleBuffered = true;
            Paint += Form_Paint;

            float s = 100;
            cubeVerts[0] = new Vector3D(-s, -s, -s); cubeVerts[1] = new Vector3D(s, -s, -s);
            cubeVerts[2] = new Vector3D(s,  s, -s); cubeVerts[3] = new Vector3D(-s,  s, -s);
            cubeVerts[4] = new Vector3D(-s, -s,  s); cubeVerts[5] = new Vector3D(s, -s,  s);
            cubeVerts[6] = new Vector3D(s,  s,  s); cubeVerts[7] = new Vector3D(-s,  s,  s);

            timer.Interval = 16;
            timer.Tick += (s2, e) => { rotX += 0.01f; rotY += 0.015f; rotZ += 0.005f; Invalidate(); };
            timer.Start();
            FormClosed += (s2, e) => timer.Stop();
        }

        private Vector3D RotateX(Vector3D v, float a)
        {
            float c = (float)Math.Cos(a), s = (float)Math.Sin(a);
            return new Vector3D(v.X, v.Y * c - v.Z * s, v.Y * s + v.Z * c);
        }
        private Vector3D RotateY(Vector3D v, float a)
        {
            float c = (float)Math.Cos(a), s = (float)Math.Sin(a);
            return new Vector3D(v.X * c + v.Z * s, v.Y, -v.X * s + v.Z * c);
        }
        private Vector3D RotateZ(Vector3D v, float a)
        {
            float c = (float)Math.Cos(a), s = (float)Math.Sin(a);
            return new Vector3D(v.X * c - v.Y * s, v.X * s + v.Y * c, v.Z);
        }

        private PointF Project(Vector3D v)
        {
            float scale = 400 / (v.Z + 300);
            return new PointF(
                ClientSize.Width / 2 + v.X * scale,
                ClientSize.Height / 2 + v.Y * scale);
        }

        private void Form_Paint(object sender, PaintEventArgs e)
        {
            e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;
            e.Graphics.Clear(Color.Black);

            for (int i = 0; i < cubeVerts.Length; i++)
            {
                var v = RotateX(cubeVerts[i], rotX);
                v = RotateY(v, rotY);
                v = RotateZ(v, rotZ);
                projected[i] = v;
            }

            using (var pen = new Pen(Color.Cyan, 2))
            {
                // передняя грань
                DrawEdge(e.Graphics, pen, 0, 1); DrawEdge(e.Graphics, pen, 1, 2);
                DrawEdge(e.Graphics, pen, 2, 3); DrawEdge(e.Graphics, pen, 3, 0);
                // задняя грань
                DrawEdge(e.Graphics, pen, 4, 5); DrawEdge(e.Graphics, pen, 5, 6);
                DrawEdge(e.Graphics, pen, 6, 7); DrawEdge(e.Graphics, pen, 7, 4);
                // боковые рёбра
                DrawEdge(e.Graphics, pen, 0, 4); DrawEdge(e.Graphics, pen, 1, 5);
                DrawEdge(e.Graphics, pen, 2, 6); DrawEdge(e.Graphics, pen, 3, 7);
            }

            using (var brush = new SolidBrush(Color.Yellow))
            {
                foreach (var v in projected)
                {
                    var p = Project(v);
                    e.Graphics.FillEllipse(brush, p.X - 4, p.Y - 4, 8, 8);
                }
            }
            e.Graphics.DrawString("Вращающийся 3D-куб",
                new Font("Segoe UI", 10, FontStyle.Bold), Brushes.Lime, 10, 10);
        }

        private void DrawEdge(Graphics g, Pen pen, int i1, int i2)
        {
            g.DrawLine(pen, Project(projected[i1]), Project(projected[i2]));
        }
    }
}