From f30a8ee2a8e0317d11d70c348bdd9c7cd15844c8 Mon Sep 17 00:00:00 2001
From: gm-matthew <108370479+gm-matthew@users.noreply.github.com>
Date: Tue, 4 Jun 2024 16:40:36 +0100
Subject: [PATCH 1/2] Minor shader optimization If the mipmap level is 0.0, we
 only need to run texBiLinear() for the highest quality texture mipmap Adds
 around 10-20% more performance in Daytona 2

---
 Src/Graphics/New3D/R3DShaderCommon.h | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/Src/Graphics/New3D/R3DShaderCommon.h b/Src/Graphics/New3D/R3DShaderCommon.h
index df12c1b..df392ea 100644
--- a/Src/Graphics/New3D/R3DShaderCommon.h
+++ b/Src/Graphics/New3D/R3DShaderCommon.h
@@ -249,15 +249,22 @@ vec4 textureR3D(usampler2D texSampler, ivec2 wrapMode, ivec2 texSize, ivec2 texP
 	int iLevel = int(fLevel);
 
 	ivec2 texPos0 = GetTexturePosition(iLevel,texPos);
-	ivec2 texPos1 = GetTexturePosition(iLevel+1,texPos);
-
 	ivec2 texSize0 = GetTextureSize(iLevel, texSize);
-	ivec2 texSize1 = GetTextureSize(iLevel+1, texSize); 
 
-	vec4 texLevel0 = texBiLinear(texSampler, wrapMode, vec2(texSize0), texPos0, texCoord);
-	vec4 texLevel1 = texBiLinear(texSampler, wrapMode, vec2(texSize1), texPos1, texCoord);
+	if (fLevel > 0)
+	{
+		ivec2 texPos1 = GetTexturePosition(iLevel+1,texPos);
+		ivec2 texSize1 = GetTextureSize(iLevel+1, texSize); 
 
-	return mix(texLevel0, texLevel1, fract(fLevel));	// linear blend between our mipmap levels
+		vec4 texLevel0 = texBiLinear(texSampler, wrapMode, vec2(texSize0), texPos0, texCoord);
+		vec4 texLevel1 = texBiLinear(texSampler, wrapMode, vec2(texSize1), texPos1, texCoord);
+
+		return mix(texLevel0, texLevel1, fract(fLevel));	// linear blend between our mipmap levels
+	}
+	else
+	{
+		return texBiLinear(texSampler, wrapMode, vec2(texSize0), texPos0, texCoord);
+	}
 }
 
 vec4 GetTextureValue()

From 42e236be0dabf6cbda248e131d84459d8c268e6d Mon Sep 17 00:00:00 2001
From: gm-matthew <108370479+gm-matthew@users.noreply.github.com>
Date: Sun, 9 Jun 2024 22:04:53 +0100
Subject: [PATCH 2/2] Add comment briefly explaining optimization

---
 Src/Graphics/New3D/R3DShaderCommon.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Src/Graphics/New3D/R3DShaderCommon.h b/Src/Graphics/New3D/R3DShaderCommon.h
index df392ea..f1b39f1 100644
--- a/Src/Graphics/New3D/R3DShaderCommon.h
+++ b/Src/Graphics/New3D/R3DShaderCommon.h
@@ -263,6 +263,7 @@ vec4 textureR3D(usampler2D texSampler, ivec2 wrapMode, ivec2 texSize, ivec2 texP
 	}
 	else
 	{
+		// if fLevel is 0, no need to mix with next mipmap level; slight performance boost
 		return texBiLinear(texSampler, wrapMode, vec2(texSize0), texPos0, texCoord);
 	}
 }