rtl/gfx: implement perspective-corrected barycentric coordinates

4 files changed, 105 insertions, 14 deletions

diff --git a/gfx_hw.tcl b/gfx_hw.tcl
index 0836a80..ffe9a43 100644
--- a/gfx_hw.tcl
+++ b/gfx_hw.tcl
@@ -72,6 +72,7 @@ add_fileset_file gfx_clear.sv SYSTEM_VERILOG PATH rtl/gfx/gfx_clear.sv
 add_fileset_file gfx_lerp.sv SYSTEM_VERILOG PATH rtl/gfx/gfx_lerp.sv
 add_fileset_file gfx_frag.sv SYSTEM_VERILOG PATH rtl/gfx/gfx_frag.sv
 add_fileset_file gfx_frag_addr.sv SYSTEM_VERILOG PATH rtl/gfx/gfx_frag_addr.sv
+add_fileset_file gfx_frag_bary.sv SYSTEM_VERILOG PATH rtl/gfx/gfx_frag_bary.sv
 add_fileset_file gfx_frag_shade.sv SYSTEM_VERILOG PATH rtl/gfx/gfx_frag_shade.sv
 add_fileset_file gfx_frag_funnel.sv SYSTEM_VERILOG PATH rtl/gfx/gfx_frag_funnel.sv
 
diff --git a/rtl/gfx/gfx_defs.sv b/rtl/gfx/gfx_defs.sv
index bffbb1f..7da259a 100644
--- a/rtl/gfx/gfx_defs.sv
+++ b/rtl/gfx/gfx_defs.sv
@@ -67,6 +67,10 @@ typedef struct packed
 typedef logic signed[31:0] fixed;
 typedef fixed[2:0]         fixed_tri;
 
+`define EDGE_P0_TO_P1 0
+`define EDGE_P1_TO_P2 1
+`define EDGE_P2_TO_P0 2
+
 typedef struct packed
 {
 	fixed x, y;
@@ -134,6 +138,8 @@ typedef struct packed
 } frag_paint;
 
 `define GFX_FRAG_ADDR_STAGES  3
+`define GFX_FRAG_BARY_STAGES  (`FIXED_DIV_STAGES + 2 + `FIXED_DIV_STAGES)
 `define GFX_FRAG_SHADE_STAGES (`LERP_STAGES + 1)
+`define GFX_FRAG_STAGES       (`GFX_FRAG_BARY_STAGES + `GFX_FRAG_SHADE_STAGES)
 
 `endif
diff --git a/rtl/gfx/gfx_frag.sv b/rtl/gfx/gfx_frag.sv
index b4481ce..79fb2b4 100644
--- a/rtl/gfx/gfx_frag.sv
+++ b/rtl/gfx/gfx_frag.sv
@@ -20,17 +20,17 @@ module gfx_frag
 	gfx_frag_funnel funnel
 	(
 		.frag(funnel_frag),
-		.out_ready(addr_ready),
+		.out_ready(frag_ready),
 		.out_valid(funnel_valid),
 		.*
 	);
 
-	logic addr_ready, addr_stall;
+	logic frag_ready, frag_stall;
 
-	gfx_pipeline_flow #(.STAGES(`GFX_FRAG_SHADE_STAGES)) addr_flow
+	gfx_pipeline_flow #(.STAGES(`GFX_FRAG_STAGES)) addr_flow
 	(
-		.stall(addr_stall),
-		.in_ready(addr_ready),
+		.stall(frag_stall),
+		.in_ready(frag_ready),
 		.in_valid(funnel_valid),
 		.out_ready(1),
 		.out_valid(),
@@ -42,28 +42,34 @@ module gfx_frag
 	gfx_frag_addr addr
 	(
 		.frag(funnel_frag),
-		.stall(addr_stall),
+		.stall(frag_stall),
 		.*
 	);
 
-	localparam ADDR_WAIT_Z_STAGES = `GFX_FRAG_SHADE_STAGES - `GFX_FRAG_ADDR_STAGES;
+	localparam ADDR_WAIT_STAGES = `GFX_FRAG_STAGES - `GFX_FRAG_ADDR_STAGES;
 
-	gfx_pipes #(.WIDTH($bits(linear_coord)), .DEPTH(ADDR_WAIT_Z_STAGES)) addr_pipes
+	gfx_pipes #(.WIDTH($bits(linear_coord)), .DEPTH(ADDR_WAIT_STAGES)) addr_pipes
 	(
 		.in(linear),
 		.out(),
-		.stall(addr_stall),
+		.stall(frag_stall),
 		.*
 	);
 
-	gfx_frag_shade shade
+	fixed b1, b2;
+
+	gfx_frag_bary bary
 	(
-		.stall(addr_stall),
+		.ws(),
+		.edges(),
+		.stall(frag_stall),
+		.*
+	);
 
-		.b1(),
-		.b2(),
+	gfx_frag_shade shade
+	(
+		.stall(frag_stall),
 		.color(),
-
 		.argb0(),
 		.argb1_argb0(),
 		.argb2_argb0(),
diff --git a/rtl/gfx/gfx_frag_bary.sv b/rtl/gfx/gfx_frag_bary.sv
new file mode 100644
index 0000000..5004866
--- /dev/null
+++ b/rtl/gfx/gfx_frag_bary.sv
@@ -0,0 +1,78 @@
+`include "gfx/gfx_defs.sv"
+
+module gfx_frag_bary
+(
+	input  logic     clk,
+
+	input  fixed_tri edges,
+	                 ws,
+	input  logic     stall,
+
+	output fixed     b1,
+	                 b2
+);
+
+	fixed area, b0_w0, b1_w1, b2_w2, b1_w1_b2_w2, hold_b0_w0, hold_b1_w1, hold_b2_w2;
+	fixed_tri bs_ws, orthographic_bs;
+
+	assign b0_w0 = bs_ws[0];
+	assign b1_w1 = bs_ws[1];
+	assign b2_w2 = bs_ws[2];
+
+	assign orthographic_bs[0] = edges[`EDGE_P1_TO_P2];
+	assign orthographic_bs[1] = edges[`EDGE_P2_TO_P0];
+	assign orthographic_bs[2] = edges[`EDGE_P0_TO_P1];
+
+	genvar i;
+	generate
+		for (i = 0; i < 3; ++i) begin: vertices
+			gfx_fixed_div div_b_w
+			(
+				.z(orthographic_bs[i]),
+				.d(ws[i]),
+				.q(bs_ws[i]),
+				.*
+			);
+		end
+	endgenerate
+
+	localparam AREA_STAGES = 2;
+
+	gfx_pipes #(.WIDTH($bits(fixed)), .DEPTH(AREA_STAGES)) b1_w1_pipes
+	(
+		.in(b1_w1),
+		.out(hold_b1_w1),
+		.*
+	);
+
+	gfx_pipes #(.WIDTH($bits(fixed)), .DEPTH(AREA_STAGES)) b2_w2_pipes
+	(
+		.in(b2_w2),
+		.out(hold_b2_w2),
+		.*
+	);
+
+	gfx_fixed_div norm_b1
+	(
+		.z(hold_b1_w1),
+		.d(area),
+		.q(b1),
+		.*
+	);
+
+	gfx_fixed_div norm_b2
+	(
+		.z(hold_b2_w2),
+		.d(area),
+		.q(b2),
+		.*
+	);
+
+	always_ff @(posedge clk)
+		if (!stall) begin
+			area <= hold_b0_w0 + b1_w1_b2_w2;
+			hold_b0_w0 <= b0_w0;
+			b1_w1_b2_w2 <= b1_w1 + b2_w2;
+		end
+
+endmodule