From 1ce53491999e8d72219dcfa10d45c6fb87014984 Mon Sep 17 00:00:00 2001
From: kd-11 <karokidii@gmail.com>
Date: Mon, 20 Dec 2021 00:48:47 +0300
Subject: [PATCH] rsx: Remove zclip hackery

- Calculates precise Z value as requested by the game
- Works properly if the underlying Z format matches the PS3 1:1 but may cause minor problems otherwise
---
 rpcs3/Emu/RSX/Program/GLSLCommon.cpp | 24 ++++++++----------------
 1 file changed, 8 insertions(+), 16 deletions(-)

diff --git a/rpcs3/Emu/RSX/Program/GLSLCommon.cpp b/rpcs3/Emu/RSX/Program/GLSLCommon.cpp
index d8c0689323..3af0c083b7 100644
--- a/rpcs3/Emu/RSX/Program/GLSLCommon.cpp
+++ b/rpcs3/Emu/RSX/Program/GLSLCommon.cpp
@@ -603,27 +603,19 @@ namespace glsl
 		{
 			if (props.emulate_depth_clip_only)
 			{
-				// Declare rcp_precise. Requires f64 support in the drivers.
-				// This is required to handle precision drift during division for extended depth range.
-				OS <<
-				"double rcp_precise(double x)\n"
-				"{\n"
-				"	double scaled = x * 0.0009765625;\n"
-				"	double inv = 1.0 / scaled;\n"
-				"	return inv * 0.0009765625;\n"
-				"}\n"
-				"\n"
 				// Technically the depth value here is the 'final' depth that should be stored in the Z buffer.
 				// Forward mapping eqn is d' = d * (f - n) + n, where d' is the stored Z value (this) and d is the normalized API value.
+				OS <<
 				"vec4 apply_zclip_xform(const in vec4 pos, const in float near_plane, const in float far_plane)\n"
 				"{\n"
-				"	if (far_plane != 0.0 && pos.w != 0.0)\n"
+				"	if (pos.w != 0.0)\n"
 				"	{\n"
-				"		double z_range = (far_plane > near_plane)? (far_plane - near_plane) : far_plane;\n"
-				"		double inv_range = rcp_precise(z_range);\n"
-				"		float d = float(pos.z * rcp_precise(pos.w));\n"
-				"		float new_d = (d - near_plane) * float(inv_range);\n"
-				"		return vec4(pos.x, pos.y, (new_d * pos.w), pos.w);\n"
+				"		const float real_n = min(far_plane, near_plane);\n"
+				"		const float real_f = max(far_plane, near_plane);\n"
+				"		const double depth_range = double(real_f - real_n);\n"
+				"		const double inv_range = (depth_range > 0.0) ? (1.0 / (depth_range * pos.w)) : 0.0;\n"
+				"		const double d = (double(pos.z) - real_n) * inv_range;\n"
+				"		return vec4(pos.xy, float(d * pos.w), pos.w);\n"
 				"	}\n"
 				"	else\n"
 				"	{\n"