Interactive mandelbrot: use quadtree table for nicer previews

examples/mandelbrot/mandelbrot-interactive.csn

@@ -5,10 +5,6 @@
     (def H 768)
     (def MAXITER 50)
 
-    ; size of big pixels
-    (def COL_SKIP 8)
-    (def ROW_SKIP 8)
-
     (lds @cout "Interactive Mandelbrot\n")
     (lds @cout "----------------------\n")
     (lds @cout "Navigate using WASD, zoom using Q/E\n")
@@ -20,8 +16,46 @@
     (sym mb_y r3)
     (sym mb_s r4)
     (sym mb_row r5)
-    (sym mb_col_skip r6)
-    (sym mb_row_skip r7)
+
+    ; index into the skip/size table
+    (sym mb_skip_index r6)
+
+    ; size of big pixels
+    (def COL_SKIP 8)
+    (def ROW_SKIP 8)
+    ; incrementally renders 1x1, 2x2, 4x4, ...
+    (def MB_SKIP_TABLE_SIZE 80)
+    (def MB_SKIP_REPEAT_INDEX 16)
+    (sym mb_skip_table_x r7)
+    (sym mb_skip_table_y r8)
+    (sym mb_size_table r12)
+    (mkbf mb_skip_table_x (
+        0 4 0 4 2 6 0 2 4 6 2 6 0 2 4 6
+        ; 8x8 grid
+        1 3 5 7 1 3 5 7 1 3 5 7 1 3 5 7
+        0 2 4 6 0 2 4 6 0 2 4 6 0 2 4 6
+        1 3 5 7 1 3 5 7 1 3 5 7 1 3 5 7
+        ; do top left pixels again
+        0 2 4 6 0 2 4 6 0 2 4 6 0 2 4 6
+    ))
+    (mkbf mb_skip_table_y (
+        0 0 4 4 0 0 2 2 2 2 4 4 6 6 6 6
+        ; 8x8 grid
+        0 0 0 0 2 2 2 2 4 4 4 4 6 6 6 6
+        1 1 1 1 3 3 3 3 5 5 5 5 7 7 7 7
+        1 1 1 1 3 3 3 3 5 5 5 5 7 7 7 7
+        ; do top left pixels again
+        0 0 0 0 2 2 2 2 4 4 4 4 6 6 6 6
+    ))
+    (mkbf mb_size_table (
+        8 4 4 4 2 2 2 2 2 2 2 2 2 2 2 2
+        ; 8x8 grid
+        1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
+        1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
+        1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
+        ; do top left pixels again
+        1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
+    ))
 
     (ld mb_x 0.0)
     (ld mb_y 0.0)
@@ -31,13 +65,13 @@
     (ld is_first_render 1)
 
     ; render row
-    ; big - is this the first render? if yes, use big pixels
-    ; col - mb_col_skip column offset
+    ; size - pixel size
+    ; col - column offset
     ; px - offset x
     ; py - offset y
     ; scale - scaling
     ; row - row position
-    (proc render_row big col px py scale row
+    (proc render_row size col px py scale row
         (sym gradient r9)
         (mkbf gradient (
             0x421e0f 0x19071a 0x09012f 0x040449 0x000764 0x0c2c8a 0x1852b1 0x397dd1 
@@ -57,13 +91,7 @@
                 )
                 (else? (ld r0 0))
             )
-            (cmp big 1)
-            (j.ne :not_big)
-            (sc-rect x y COL_SKIP ROW_SKIP r0)
-            (j :was_big)
-            (:not_big)
-            (sc-wr x y r0)
-            (:was_big)
+            (sc-rect x y size size r0)
             (add x COL_SKIP)
             (cmp x W)
             (j.lt :col)
@@ -126,14 +154,19 @@
 
         ; mark this as a first render and reset col_skip and row_skip
         (ld is_first_render 1)
-        (ld mb_col_skip 0)
-        (ld mb_row_skip 0)
+        (ld mb_skip_index 0)
     (:did_not_move)
 
-    ; render row mb_row + mb_row_skip
+    (sym mb_col_skip r9)
+    (sym mb_row_skip r11)
+    (bfrd mb_col_skip @mb_skip_table_x mb_skip_index)
+    (bfrd mb_row_skip @mb_skip_table_y mb_skip_index)
+    (bfrd r1 @mb_size_table mb_skip_index)
+
+    ; render row mb_row + row skip
     (ld r0 mb_row)
     (add r0 mb_row_skip)
-    (call render_row is_first_render mb_col_skip mb_x mb_y mb_s r0)
+    (call render_row r1 mb_col_skip mb_x mb_y mb_s r0)
 
     (cmp mb_row H)
         (j.ge :render_done)
@@ -143,16 +176,14 @@
     (:render_done)
         ; otherwise, this frame is done
         (ld mb_row 0)
-        (add mb_col_skip 1)
+        (add mb_skip_index 1)
         (ld is_first_render 0)
-        (mod mb_col_skip COL_SKIP)
-
-        ; if mb_col_skip wrapped back to zero increase mb_row_skip
-        (cmp mb_col_skip 0)
-        (j.ne :not_col)
-        (add mb_row_skip 1)
-        (mod mb_row_skip ROW_SKIP)
-        (:not_col)
+
+        (cmp mb_skip_index MB_SKIP_TABLE_SIZE)
+            ; if skip index is out of bounds, go back to repeating area
+            (j.lt :not_end)
+            (ld mb_skip_index MB_SKIP_REPEAT_INDEX)
+        (:not_end)
     (:render_not_done)
     (j :slp)