From 77e510bd907dcf83b8b403e1ee8e689837f4c72d Mon Sep 17 00:00:00 2001
From: "Unknown W. Brackets" <checkins@unknownbrackets.org>
Date: Sun, 4 Dec 2022 19:27:23 -0800
Subject: [PATCH] GPU: Use accurate depth for depth range hack.

This should be easier to ensure stays well tested.
---
 GPU/GLES/GPU_GLES.cpp          |  5 -----
 GPU/GLES/ShaderManagerGLES.cpp | 32 --------------------------------
 GPU/GPUCommon.cpp              |  5 +++++
 GPU/GPUState.cpp               |  6 +++---
 GPU/GPUState.h                 |  2 +-
 5 files changed, 9 insertions(+), 41 deletions(-)

diff --git a/GPU/GLES/GPU_GLES.cpp b/GPU/GLES/GPU_GLES.cpp
index a707915eb1..380fe2d2c7 100644
--- a/GPU/GLES/GPU_GLES.cpp
+++ b/GPU/GLES/GPU_GLES.cpp
@@ -173,11 +173,6 @@ u32 GPU_GLES::CheckGPUFeatures() const {
 	if (gl_extensions.ARB_texture_float || gl_extensions.OES_texture_float)
 		features |= GPU_USE_TEXTURE_FLOAT;
 
-	// The Phantasy Star hack :(
-	if (PSP_CoreParameter().compat.flags().DepthRangeHack && (features & GPU_USE_ACCURATE_DEPTH) == 0) {
-		features |= GPU_USE_DEPTH_RANGE_HACK;
-	}
-
 	if (!draw_->GetShaderLanguageDesc().bitwiseOps) {
 		features |= GPU_USE_FRAGMENT_TEST_CACHE;
 	}
diff --git a/GPU/GLES/ShaderManagerGLES.cpp b/GPU/GLES/ShaderManagerGLES.cpp
index 7e4ae0f881..cc5211a19f 100644
--- a/GPU/GLES/ShaderManagerGLES.cpp
+++ b/GPU/GLES/ShaderManagerGLES.cpp
@@ -319,38 +319,6 @@ static inline void FlipProjMatrix(Matrix4x4 &in, bool useBufferedRendering) {
 		in[8] = -in[8];
 		in[12] = -in[12];
 	}
-
-	// In Phantasy Star Portable 2, depth range sometimes goes negative and is clamped by glDepthRange to 0,
-	// causing graphics clipping glitch (issue #1788). This hack modifies the projection matrix to work around it.
-	if (gstate_c.Use(GPU_USE_DEPTH_RANGE_HACK)) {
-		float zScale = gstate.getViewportZScale() / 65535.0f;
-		float zCenter = gstate.getViewportZCenter() / 65535.0f;
-
-		// if far depth range < 0
-		if (zCenter + zScale < 0.0f) {
-			// if perspective projection
-			if (in[11] < 0.0f) {
-				float depthMax = gstate.getDepthRangeMax() / 65535.0f;
-				float depthMin = gstate.getDepthRangeMin() / 65535.0f;
-
-				float a = in[10];
-				float b = in[14];
-
-				float n = b / (a - 1.0f);
-				float f = b / (a + 1.0f);
-
-				f = (n * f) / (n + ((zCenter + zScale) * (n - f) / (depthMax - depthMin)));
-
-				a = (n + f) / (n - f);
-				b = (2.0f * n * f) / (n - f);
-
-				if (!my_isnan(a) && !my_isnan(b)) {
-					in[10] = a;
-					in[14] = b;
-				}
-			}
-		}
-	}
 }
 
 static inline bool GuessVRDrawingHUD(bool is2D, bool flatScreen) {
diff --git a/GPU/GPUCommon.cpp b/GPU/GPUCommon.cpp
index 20d97649df..bbfa7f3090 100644
--- a/GPU/GPUCommon.cpp
+++ b/GPU/GPUCommon.cpp
@@ -3537,6 +3537,11 @@ u32 GPUCommon::CheckGPUFeatures() const {
 		features |= GPU_USE_CLEAR_RAM_HACK;
 	}
 
+	// Even without depth clamp, force accurate depth on for some games that break without it.
+	if (PSP_CoreParameter().compat.flags().DepthRangeHack) {
+		features |= GPU_USE_ACCURATE_DEPTH;
+	}
+
 	return features;
 }
 
diff --git a/GPU/GPUState.cpp b/GPU/GPUState.cpp
index 95568e1e93..ba0e650bb6 100644
--- a/GPU/GPUState.cpp
+++ b/GPU/GPUState.cpp
@@ -375,7 +375,7 @@ static const char *const gpuUseFlagNames[32] = {
 	"GPU_USE_VS_RANGE_CULLING",
 	"GPU_USE_BLEND_MINMAX",
 	"GPU_USE_LOGIC_OP",
-	"GPU_USE_DEPTH_RANGE_HACK",
+	"N/A",
 	"GPU_USE_TEXTURE_NPOT",
 	"GPU_USE_ANISOTROPY",
 	"GPU_USE_CLEAR_RAM_HACK",
@@ -388,7 +388,7 @@ static const char *const gpuUseFlagNames[32] = {
 	"GPU_USE_DEPTH_TEXTURE",
 	"GPU_USE_ACCURATE_DEPTH",
 	"GPU_USE_GS_CULLING",
-	"GPU_USE_REVERSE_COLOR_ORDER",
+	"N/A",
 	"GPU_USE_FRAMEBUFFER_FETCH",
 	"GPU_SCALE_DEPTH_FROM_24BIT_TO_16BIT",
 	"GPU_ROUND_FRAGMENT_DEPTH_TO_16BIT",
@@ -409,4 +409,4 @@ const char *GpuUseFlagToString(int useFlag) {
 	} else {
 		return "N/A";
 	}
-}
\ No newline at end of file
+}
diff --git a/GPU/GPUState.h b/GPU/GPUState.h
index 02fba9c309..e5acb39a18 100644
--- a/GPU/GPUState.h
+++ b/GPU/GPUState.h
@@ -478,7 +478,7 @@ enum {
 	GPU_USE_VS_RANGE_CULLING = FLAG_BIT(3),
 	GPU_USE_BLEND_MINMAX = FLAG_BIT(4),
 	GPU_USE_LOGIC_OP = FLAG_BIT(5),
-	GPU_USE_DEPTH_RANGE_HACK = FLAG_BIT(6),
+	// Bit 6 is free.
 	GPU_USE_TEXTURE_NPOT = FLAG_BIT(7),
 	GPU_USE_ANISOTROPY = FLAG_BIT(8),
 	GPU_USE_CLEAR_RAM_HACK = FLAG_BIT(9),