From eee66720b7f0b5560da46c5edbaab8764b58c6bb Mon Sep 17 00:00:00 2001
From: "Zed A. Shaw" <zed.shaw@gmail.com>
Date: Mon, 13 Jan 2025 22:42:48 -0500
Subject: [PATCH] Annotate the ceiling/floor rendering.

---
 sfmlcaster.cpp | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/sfmlcaster.cpp b/sfmlcaster.cpp
index bf64b2e..66118b3 100644
--- a/sfmlcaster.cpp
+++ b/sfmlcaster.cpp
@@ -37,6 +37,9 @@ const float STEP_ANGLE = FOV / CASTED_RAYS;
 const int MAX_DEPTH = MAP_SIZE * TILE_SIZE;
 const float SCALE = (SCREEN_WIDTH / 2) / CASTED_RAYS;
 int PITCH=0;
+// I chose fixed textures for this instead
+const int floorTexture = 3;
+const int ceilingTexture = 6;
 
 float player_x = SCREEN_WIDTH / 4;
 float player_y = SCREEN_WIDTH / 4;
@@ -288,39 +291,60 @@ void draw_ceiling_floor(sf::RenderWindow &window) {
   int screenWidth = THREED_VIEW_HEIGHT;
 
   for(int y = screenHeight / 2 + 1; y < screenHeight; ++y) {
+    // rayDir for leftmost ray (x=0) and rightmost (x = w)
     float rayDirX0 = dirX - planeX;
     float rayDirY0 = dirY - planeY;
     float rayDirX1 = dirX + planeX;
     float rayDirY1 = dirY + planeY;
 
+    // current y position compared to the horizon
     int p = y - screenHeight / 2;
 
+    // vertical position of the camera
+    // 0.5 will the camera at the center horizon. For a
+    // different value you need a separate loop for ceiling
+    // and floor since they're no longer symmetrical.
     float posZ = 0.5 * screenHeight;
+
+    // horizontal distance from the camera to the floor for the current row
+    // 0.5 is the z position exactly in the middle between floor and ceiling
+    // See NOTE in Lode's code for more.
     float rowDistance = posZ / p;
 
+    // calculate the real world step vector we have to add for each x (parallel to camera plane)
+    // adding step by step avoids multiplications with a wight in the inner loop
     float floorStepX = rowDistance * (rayDirX1 - rayDirX0) / screenWidth;
     float floorStepY = rowDistance * (rayDirY1 - rayDirY0) / screenWidth;
 
+
+    // real world coordinates of the leftmost column.
+    // This will be updated as we step to the right
     float floorX = posX + rowDistance * rayDirX0;
     float floorY = posY + rowDistance * rayDirY0;
 
     for(int x = 0; x < screenWidth; ++x) {
+      // the cell coord is simply taken from the int parts of
+      // floorX and floorY.
       int cellX = int(floorX);
       int cellY = int(floorY);
 
+      // get the texture coordinat from the fractional part
       int tx = int(texWidth * (floorX - cellX)) & (texWidth - 1);
       int ty = int(texWidth * (floorY - cellY)) & (texHeight - 1);
 
       floorX += floorStepX;
       floorY += floorStepY;
 
-      int floorTexture = 3;
-      int ceilingTexture = 6;
-
+      // now get the pixel from the texture
       uint32_t color;
+      // this uses the previous ty/tx fractional parts of
+      // floorX cellX to find the texture x/y. How?
+
+      // FLOOR
       color = texture[floorTexture][texWidth * ty + tx];
       pixels[pixcoord(x, y)] = color;
 
+      // CEILING
       color = texture[ceilingTexture][texWidth * ty + tx];
       pixels[pixcoord(x, screenHeight - y - 1)] = color;
     }