Create Elementary cellular automata

Cellular automata now makes a new row
every frame and resets at the top.

1 files changed, 98 insertions, 34 deletions

diff --git a/main.fab b/main.fab
index 8624f9d..a47ec27 100644
--- a/main.fab
+++ b/main.fab
@@ -1,54 +1,118 @@
 vars
-  U[8] buf      // A buffer that can store the current and next row
-  U row_a = 0   // We swap back and forth between these two offsets for each row
-  U row_b = 4
-  UU drawing_row_offset = 0// Use this to track which row we're drawing
+  U[64] buf         // A buffer that can store the current and next row
+  U curr_gen = 0       // Swap these offsets back and forth per generation
+  U next_gen = 32
+  UU drawing_row_offset = 0  // Use this to track which row we're drawing
   U current_rule = %00011110
-  U next_cell = 0
 
 fn init_screen()
-  ppu_reset_addr($2000)
+  // Scroll to attributes
+  ppu_reset_addr($2000 + 960)
+  // Set attributes for background
+  for U i = 0; i < 64; i+= 1
+    {PPUDATA}(%11111111)
 
-  // Set background tiles
-  for UU i = 0; i < 960; i += 1
-    {PPUDATA}(1)
+  //// Init the buffers to 0
+  //for i = 0; i < 64; i += 1
+  //  buf[i] = 0
 
-  U i = 0
-  // Set attributes for background
-  for i = 0; i < 64; i+= 1
-    {PPUDATA}(%00011011)
+  // Init the buffer to zero
+  buf = U[64]()
+  // Add an initial cell
+  buf[16] = 1
 
-  // Init the buffers to 0
-  for i = 0; i < 8; i += 1
-    buf[i] = 0
 
-fn calc_and_upload_next_row()
-  // "scroll" to the row we're at
-  UU row_start = $2000
-  row_start += (drawing_row_offset * 32)
-  ppu_reset_addr(row_start)
+fn assemble_code(U left, U middle, U right) U
+  U out = %00000000
+  out |= left << 2
+  out |= middle << 1
+  out |= right
+  return out
 
-  for UU i = 0; i < 32; i += 1
-    //next_cell = 0 //get_next_gen(i)
-    {PPUDATA}(next_cell)
+fn calc_next_cell(U left, U middle, U right) U
+  U code = assemble_code(left, middle, right)
+  ct U mask7 = %10000000
+  ct U mask6 = %01000000
+  ct U mask5 = %00100000
+  ct U mask4 = %00010000
+  ct U mask3 = %00001000
+  ct U mask2 = %00000100
+  ct U mask1 = %00000010
+  ct U mask0 = %00000001
+  switch code
+    case %00000111
+      return (current_rule & mask7) >> 7
+    case %00000110
+      return (current_rule & mask6) >> 6
+    case %00000101
+      return (current_rule & mask5) >> 5
+    case %00000100
+      return (current_rule & mask4) >> 4
+    case %00000011
+      return (current_rule & mask3) >> 3
+    case %00000010
+      return (current_rule & mask2) >> 2
+    case %00000001
+      return (current_rule & mask1) >> 1
+    case %00000000
+      return (current_rule & mask0) >> 0
 
-  drawing_row_offset += 1
+fn calc_and_advance_gen()
+  // Calculate the next row's values
+  U left_ind = 0
+  U right_ind = 0
+  U left_cell = 0
+  U mid_cell = 0
+  U right_cell = 0
+  U next_cell = 0
+  for U i = 0; i < 32; i += 1
+    // Calculate indices for left and right of cell
+    if i == 0
+      left_ind = 31
+    else
+      left_ind = i - 1
+    if i == 31
+      right_ind = 0
+    else
+      right_ind = i + 1
+    // Get left and right of cell
+    left_cell = buf[curr_gen + left_ind]
+    mid_cell = buf[curr_gen + i]
+    right_cell = buf[curr_gen + right_ind]
+    // Calc next cell
+    next_cell = calc_next_cell(left_cell, mid_cell, right_cell)
+    // Set next cell
+    buf[next_gen + i] = next_cell
 
+  // Advance next generation
+  if curr_gen == 0
+    curr_gen = 32
+    next_gen = 0
+  else
+    curr_gen = 0
+    next_gen = 32
+
+  // advance drawing row offset, looping back to top
+  drawing_row_offset += 1
   if drawing_row_offset == 30
     drawing_row_offset = 0
-    if next_cell
-      next_cell = 0
-    else
-      next_cell = 1
 
-nmi main_nmi()
-  ppu_upload_oam_poll_pads(0)
+fn upload_curr_gen()
+  // "scroll" to the row we're at
+  UU row_start = $2000
+  row_start += (drawing_row_offset * 32)
+  ppu_reset_addr(row_start)
+  for U i = 0; i < 32; i += 1 //32 columns
+    //next_cell = 0 //get_next_gen(i)
+    {PPUDATA}(buf[i+curr_gen])
 
-  calc_and_upload_next_row()
 
+nmi main_nmi()
   // Turn on rendering sprites and bg
   {PPUMASK}(PPUMASK_ON | PPUMASK_NO_CLIP)
 
+  upload_curr_gen()
+
   ppu_reset_scroll(0, 0)
 
 
@@ -58,7 +122,7 @@ mode main()
   palette = example_palette
   ppu_upload_palette()
 
-  // Load the background
+  // Initialize the screen
   init_screen()
 
   // Turn the NMI on
@@ -66,8 +130,8 @@ mode main()
 
   // Loop forever:
   while true
-    update_pads()
     nmi
+    calc_and_advance_gen()
 
 // Define the tileset (commonly called CHR):
 chrrom