Draw "walls" with corrected fish-eye

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

raycaster.c

@@ -98,8 +98,13 @@ void drawRays3D()
 {
   int r, mx, my, mp, dof;
 
-  // Ray x, y, ray angle
-  float rx, ry, ra, xo, yo;
+  // Ray x, y, angle
+  float rx, ry, ra;
+
+  float xo, yo;
+
+  // Final distance
+  float disT;
 
   // Let's initialize the ray angle n degrees from the player's facing position
   // ra = ray angle; pa = player angle; DR = degree radian; n = degrees to use
@@ -116,7 +121,7 @@ void drawRays3D()
   }
 
   // * Cast n rays
-  for (r = 0; r < 360; r++)
+  for (r = 0; r < 60; r++)
   {
     // * --- Check Horizontal Lines ---
     dof = 0;
@@ -281,12 +286,14 @@ void drawRays3D()
     {
       rx = vx;
       ry = vy;
+      disT = disV;
     }
 
     if (disH < disV)
     {
       rx = hx;
       ry = hy;
+      disT = disH;
     }
 
     // * Draw the shortest line
@@ -297,6 +304,47 @@ void drawRays3D()
     glVertex2i(rx, ry);
     glEnd();
 
+    // * --- Draw 3D Walls ---
+
+    // Correct the fish-eye effect
+
+    float ca = pa - ra;
+    if (ra < 0)
+    {
+      ra += 2 * PI;
+    }
+    if (ra > 2 * PI)
+    {
+      ra -= 2 * PI;
+    }
+
+    disT = disT * cos(ca);
+
+    // The window will be 320x160 px
+    // The formula for each line height will be the cube size (64) times our
+    // screen height (320), divided by the ray distance (disT).
+    // The further away, the larger the distance and the shorter the final line
+    // height will be.
+    float lineH = (mapS * 320) / disT;
+
+    // We need to offset the line to the middle of the screen
+    // That's the full window height, minus half the line height
+    float lineO = 160 - lineH / 2;
+
+    // Let's make sure the line doesn't exceed our vertical space, so we cap it
+    if (lineH > 320)
+    {
+      lineH = 320;
+    }
+
+    // * Draw the "wall" line
+    glLineWidth(8);
+    glBegin(GL_LINES);
+    // Draw the line every 8th pixel, and shift the viewport to the right by 530
+    glVertex2i(r * 8 + 530, lineO);
+    glVertex2i(r * 8 + 530, lineH + lineO);
+    glEnd();
+
     // * Increase the ray angle to draw the next ray
     ra += DR;
     if (ra < 0)