doom from scratch - 2018/04/21

DoomFromScratch.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

using static System.Math;

namespace DoomFromScratch
{
    public partial class Form1 : Form
    {
        Graphics g1, g2, g3;

        private int
            wx1 = 4, wy1 = 4,
            wx2 = 292, wy2 = 292;

        private int
            vx1 = 140, vy1 = 40,
            vx2 = 140, vy2 = 140;

        private float px = 50, py = 50;
        private int plen = 10;
        private double angle = 0;

        public Form1()
        {
            InitializeComponent();

            g1 = panel1.CreateGraphics();
            g2 = panel2.CreateGraphics();
            g3 = panel3.CreateGraphics();

            this.Shown += (s, e) => this.Size = new Size(1100, Height);
        }

        private void panel1_Paint(object sender, PaintEventArgs e)
        {
            g1.DrawRectangle(Pens.Blue, wx1, wy1, wx2 - wx1, wy2 - wy1);
            g1.DrawLine(Pens.Yellow, vx1, vy1, vx2, vy2);
            g1.DrawLine(Pens.Gray, px, py,
                px + (float)Cos(angle) * plen, py + (float)Sin(angle) * plen);
            g1.FillRectangle(Brushes.White, px, py, 1, 1);
        }

        private void panel2_Paint(object sender, PaintEventArgs e)
        {
            float cos = (float)Cos(angle), sin = (float)Sin(angle);

            float cx = 150, cy = 150; // center
            float tx1 = vx1 - px, ty1 = vy1 - py,
                tx2 = vx2 - px, ty2 = vy2 - py;
            float tz1 = tx1 * cos + ty1 * sin;
            float tz2 = tx2 * cos + ty2 * sin;
            tx1 = tx1 * sin - ty1 * cos;
            tx2 = tx2 * sin - ty2 * cos;
            
            g2.DrawLine(Pens.Yellow, cx - tx1, cy - tz1, cx - tx2, cy - tz2);
            g2.DrawLine(Pens.Gray, cx, cy, cx, cy - plen);
            g2.FillRectangle(Brushes.White, cx, cy, 1, 1);
        }

        private void panel3_Paint(object sender, PaintEventArgs e)
        {
            float cos = (float)Cos(angle), sin = (float)Sin(angle);

            float cx = 150, cy = 150; // center
            float tx1 = vx1 - px, ty1 = vy1 - py,
                tx2 = vx2 - px, ty2 = vy2 - py;
            float tz1 = tx1 * cos + ty1 * sin;
            float tz2 = tx2 * cos + ty2 * sin;
            tx1 = tx1 * sin - ty1 * cos;
            tx2 = tx2 * sin - ty2 * cos;

            float height = 150;

            if (tz1 > 0 || tz2 > 0)
            {
                Intersect(tx1, tz1, tx2, tz2, -0.0001f, 0.0001f, -20, 5, out var ix1, out var iz1);
                Intersect(tx1, tz1, tx2, tz2, 0.0001f, 0.0001f, 20, 5, out var ix2, out var iz2);

                if (tz1 <= 0)
                {
                    if (iz1 > 0)
                    {
                        tx1 = ix1;
                        tz1 = iz1;
                    }
                    else
                    {
                        tx1 = ix2;
                        tz1 = iz2;
                    }
                }
                if (tz2 <= 0)
                {
                    if (iz1 > 0)
                    {
                        tx2 = ix1;
                        tz2 = iz1;
                    }
                    else
                    {
                        tx2 = ix2;
                        tz2 = iz2;
                    }
                }

                float x1 = -tx1 * 16 / tz1, y1a = -height / tz1, y1b = height / tz1;
                float x2 = -tx2 * 16 / tz2, y2a = -height / tz2, y2b = height / tz2;

                g3.DrawLine(Pens.Blue, cx + x1, cy + y1a, cx + x2, cy + y2a);
                g3.DrawLine(Pens.Blue, cx + x1, cy + y1b, cx + x2, cy + y2b);
                g3.DrawLine(Pens.Yellow, cx + x1, cy + y1a, cx + x1, cy + y1b);
                g3.DrawLine(Pens.Yellow, cx + x2, cy + y2a, cx + x2, cy + y2b);
            }
        }
        
        private void Form1_KeyDown(object sender, KeyEventArgs e)
        {
            switch (e.KeyCode)
            {
                case Keys.W:
                    px = px + (float)Cos(angle);
                    py = py + (float)Sin(angle);
                    break;
                case Keys.S:
                    px = px - (float)Cos(angle);
                    py = py - (float)Sin(angle);
                    break;
                case Keys.A:
                    px = px + (float)Sin(angle);
                    py = py - (float)Cos(angle);
                    break;
                case Keys.D:
                    px = px - (float)Sin(angle);
                    py = py + (float)Cos(angle);
                    break;
                case Keys.Q:
                    angle -= 0.1;
                    break;
                case Keys.E:
                    angle += 0.1;
                    break;
            }
            panel1.Invalidate();
            panel2.Invalidate();
            panel3.Invalidate();
        }

        private static float Cross(float x1, float y1, float x2, float y2)
            => x1 * y2 - y1 * x2;

        private static void Intersect(
            float x1, float y1, float x2, float y2,
            float x3, float y3, float x4, float y4,
            out float x, out float y)
        {
            x = Cross(x1, y1, x2, y2);
            y = Cross(x3, y3, x4, y4);
            var det = Cross(x1 - x2, y1 - y2, x3 - x4, y3 - y4);
            x = Cross(x, x1 - x2, y, x1 - x2) / det;
            y = Cross(x, y1 - y2, y, y3 - y4) / det;
        }
    }
}