Fix gaps and incorrect geometry at large sizes

Signed-off-by: Warrick Lo <wlo@warricklo.net>

1 files changed, 11 insertions, 7 deletions

diff --git a/task4/reuleaux.sv b/task4/reuleaux.sv
index dbf57f8..cc89f4f 100644
--- a/task4/reuleaux.sv
+++ b/task4/reuleaux.sv
@@ -20,10 +20,10 @@ module reuleaux(clk, rst_n, colour, centre_x, centre_y, diameter, start, done,
 	 * 8-bit and 13-bit numbers together. */
 	logic [20:0] diameter_scaled;
 
-	/* One bit larger since these are signed. */
-	logic signed [7:0] vga_y_next, offset_y, offset_y_next,
+	/* Extra bits to fix incorrect geometry when drawing at large radii. */
+	logic signed [8:0] vga_y_next, offset_y, offset_y_next,
 		centre_y1, centre_y2, centre_y3;
-	logic signed [8:0] vga_x_next, offset_x, offset_x_next,
+	logic signed [9:0] vga_x_next, offset_x, offset_x_next,
 		centre_x1, centre_x2, centre_x3, crit, crit_next, radius;
 
 	assign vga_colour = clear ? 3'b000 : colour;
@@ -79,9 +79,13 @@ module reuleaux(clk, rst_n, colour, centre_x, centre_y, diameter, start, done,
 	/* Only plot the pixels of the triangle. */
 	always_comb begin
 		vga_plot_next = 1'b0;
-		/* Pixels of circle 1 that are below the centre of 2 or 3. */
-		if ((octant == 3'd0) || (octant == 3'd1))
-			if (vga_y_next > centre_y2)
+		/* Pixels of circle 1 that are between the centres
+		 * of circle 2 and 3. */
+		if (octant == 3'd0)
+			if (vga_x_next <= centre_x2)
+				vga_plot_next = 1'b1;
+		if (octant == 3'd1)
+			if (vga_x_next >= centre_x3)
 				vga_plot_next = 1'b1;
 		/* Pixels of circle 2 that are to the left of the centre. */
 		if ((octant == 3'd2) || (octant == 3'd3))
@@ -141,7 +145,7 @@ module reuleaux(clk, rst_n, colour, centre_x, centre_y, diameter, start, done,
 		end else if (ready && start && ~done) begin
 			ready <= 1'b0;
 			octant <= 3'b0;
-			offset_y <= 8'b0;
+			offset_y <= 9'b0;
 			offset_x <= radius;
 			crit <= 1 - radius;
 		/* Draw the circle using the Bresenham circle algorithm. */