rtl/gfx: implement triangle setup

1 files changed, 73 insertions, 0 deletions

diff --git a/rtl/gfx/gfx_setup_bounds.sv b/rtl/gfx/gfx_setup_bounds.sv
new file mode 100644
index 0000000..6a93db2
--- /dev/null
+++ b/rtl/gfx/gfx_setup_bounds.sv
@@ -0,0 +1,73 @@
+`include "gfx/gfx_defs.sv"
+
+module gfx_setup_bounds
+(
+	input  logic      clk,
+
+	input  raster_xy  vertex_a,
+	                  vertex_b,
+	                  vertex_c,
+	input  logic      stall,
+
+	output raster_xy  reference,
+	output coarse_dim span_x,
+	                  span_y
+);
+
+	logic x_a_lt_b, x_a_lt_c, x_b_lt_c, y_a_lt_b, y_a_lt_c, y_b_lt_c;
+	raster_xy min, max, hold_a, hold_b, hold_c;
+	coarse_dim ref_x, ref_y;
+	raster_xy_prec min_prec, max_prec, ref_prec;
+
+	assign min_prec = min;
+	assign max_prec = max;
+	assign reference = ref_prec;
+
+	assign ref_prec.x.sub = 0;
+	assign ref_prec.x.fine = 0;
+	assign ref_prec.x.coarse = ref_x;
+	assign ref_prec.x.padding = 0;
+
+	assign ref_prec.y.sub = 0;
+	assign ref_prec.y.fine = 0;
+	assign ref_prec.y.coarse = ref_y;
+	assign ref_prec.y.padding = 0;
+
+	always_ff @(posedge clk)
+		if (!stall) begin
+			hold_a <= vertex_a;
+			hold_b <= vertex_b;
+			hold_c <= vertex_c;
+
+			x_a_lt_b <= vertex_a.x < vertex_b.x;
+			x_a_lt_c <= vertex_a.x < vertex_c.x;
+			x_b_lt_c <= vertex_b.x < vertex_c.x;
+
+			y_a_lt_b <= vertex_a.y < vertex_b.y;
+			y_a_lt_c <= vertex_a.y < vertex_c.y;
+			y_b_lt_c <= vertex_b.y < vertex_c.y;
+
+			if (x_a_lt_b) begin
+				min.x <= x_a_lt_c ? hold_a.x : hold_c.x;
+				max.x <= x_b_lt_c ? hold_c.x : hold_b.x;
+			end else begin
+				min.x <= x_b_lt_c ? hold_b.x : hold_c.x;
+				max.x <= x_a_lt_c ? hold_c.x : hold_a.x;
+			end
+
+			if (y_a_lt_b) begin
+				min.y <= y_a_lt_c ? hold_a.y : hold_c.y;
+				max.y <= y_b_lt_c ? hold_c.y : hold_b.y;
+			end else begin
+				min.y <= y_b_lt_c ? hold_b.y : hold_c.y;
+				max.y <= y_a_lt_c ? hold_c.y : hold_a.y;
+			end
+
+			ref_x <= min_prec.x.coarse;
+			ref_y <= min_prec.y.coarse;
+
+			span_x <= max_prec.x.coarse - min_prec.x.coarse;
+			span_y <= max_prec.y.coarse - min_prec.y.coarse;
+		end
+
+endmodule