From 09fcdbe01553385658fe437dcb1777008c0ceb39 Mon Sep 17 00:00:00 2001
From: Alejandro Soto <alejandro@34project.org>
Date: Thu, 2 Nov 2023 22:05:48 -0600
Subject: rtl/gfx: implement fine rasterization

---
 rtl/gfx/gfx_fine.sv | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 rtl/gfx/gfx_fine.sv

(limited to 'rtl/gfx/gfx_fine.sv')

diff --git a/rtl/gfx/gfx_fine.sv b/rtl/gfx/gfx_fine.sv
new file mode 100644
index 0000000..21292f2
--- /dev/null
+++ b/rtl/gfx/gfx_fine.sv
@@ -0,0 +1,48 @@
+`include "gfx/gfx_defs.sv"
+
+module gfx_fine
+#(parameter X=0, Y=0)
+(
+	input  logic     clk,
+
+	input  raster_xy pos,
+	input  fixed     corner_a,
+	                 corner_b,
+	                 corner_c,
+	input  fixed     offsets_a[`GFX_RASTER_OFFSETS],
+	                 offsets_b[`GFX_RASTER_OFFSETS],
+	                 offsets_c[`GFX_RASTER_OFFSETS],
+	input  logic     stall,
+
+	output frag_xy   fragment,
+	output logic     paint
+);
+
+	localparam INDEX = Y * `GFX_RASTER_SIZE + X;
+
+	fixed edge_a, edge_b, edge_c, offset_a, offset_b, offset_c;
+	logic sign_a, sign_b, sign_c;
+	frag_xy fragment_hold;
+
+	assign offset_a = offsets_a[INDEX];
+	assign offset_b = offsets_b[INDEX];
+	assign offset_c = offsets_c[INDEX];
+
+	assign sign_a = edge_a[$bits(edge_a) - 1];
+	assign sign_b = edge_b[$bits(edge_b) - 1];
+	assign sign_c = edge_c[$bits(edge_c) - 1];
+
+	always_ff @(posedge clk)
+		if (!stall) begin
+			paint <= !sign_a && !sign_b && !sign_c;
+	
+			fragment <= fragment_hold;
+			fragment_hold.x <= pos.x.frag.num;
+			fragment_hold.y <= pos.y.frag.num;
+
+			edge_a <= corner_a + offset_a;
+			edge_b <= corner_b + offset_b;
+			edge_c <= corner_c + offset_c;
+		end
+
+endmodule
-- 
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