From bf6b4e2e8ebb63f6b8466bc98650ce75f3bdc79f Mon Sep 17 00:00:00 2001
From: Alejandro Soto <alejandro@34project.org>
Date: Sun, 12 Nov 2023 01:37:02 -0600
Subject: rtl/gfx: implement fragment shading

---
 rtl/gfx/gfx_frag_shade.sv | 53 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)
 create mode 100644 rtl/gfx/gfx_frag_shade.sv

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

diff --git a/rtl/gfx/gfx_frag_shade.sv b/rtl/gfx/gfx_frag_shade.sv
new file mode 100644
index 0000000..d2ad7ce
--- /dev/null
+++ b/rtl/gfx/gfx_frag_shade.sv
@@ -0,0 +1,53 @@
+`include "gfx/gfx_defs.sv"
+
+module gfx_frag_shade
+(
+	input  logic            clk,
+
+	input  fixed            b1,
+	                        b2,
+	input  color_lerp_lanes argb0,
+	                        argb1_argb0,
+	                        argb2_argb0,
+	input  logic            stall,
+
+	output rgb32            color
+);
+
+	struct packed
+	{
+		logic                                    sign;
+		logic[$bits(fixed) - `FIXED_FRAC - 2:0]  out_of_range;
+		color8                                   color;
+		logic[`FIXED_FRAC - $bits(color8) - 1:0] sub;
+	} lerped[`COLOR_CHANNELS];
+
+	fixed channel_lerp[`COLOR_CHANNELS];
+	color8[`COLOR_CHANNELS - 1:0] out;
+
+	assign color = out;
+
+	genvar i;
+	generate
+		for (i = 0; i < `COLOR_CHANNELS; ++i) begin: channels
+			assign lerped[i] = channel_lerp[i];
+
+			gfx_lerp lerp
+			(
+				.q(channel_lerp[i]),
+				.q0(argb0[i]),
+				.q1_q0(argb1_argb0[i]),
+				.q2_q0(argb2_argb0[i]),
+				.*
+			);
+
+			always_ff @(posedge clk)
+				if (!stall) begin
+					out[i] <= lerped[i].color;
+					if (lerped[i].sign || |lerped[i].out_of_range)
+						out[i] <= {($bits(color8)){!lerped[i].sign}};
+				end
+		end
+	endgenerate
+
+endmodule
-- 
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