From c1088c1abc1cf540eb7e1134b3bde9ae402b514b Mon Sep 17 00:00:00 2001
From: Flameshadowxeroshin <flameshadowxeroshin@gmail.com>
Date: Mon, 2 Oct 2017 07:54:05 -0500
Subject: [PATCH] Distance field EffectMode (#1546)

* Distance field EffectMode (supports MSDF and the regular sort)
---
 Data/Shaders/GLSL/Distance field.frag | 27 +++++++++++++++++++++++++++
 Data/Shaders/GLSL/Distance field.vert | 10 ++++++++++
 src/RageDisplay_OGL.cpp               |  8 ++++++++
 src/RageTypes.cpp                     |  4 +++-
 src/RageTypes.h                       |  1 +
 5 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 Data/Shaders/GLSL/Distance field.frag
 create mode 100644 Data/Shaders/GLSL/Distance field.vert

diff --git a/Data/Shaders/GLSL/Distance field.frag b/Data/Shaders/GLSL/Distance field.frag
new file mode 100644
index 0000000000..5853eeeb2e
--- /dev/null
+++ b/Data/Shaders/GLSL/Distance field.frag	
@@ -0,0 +1,27 @@
+uniform sampler2D Texture1;
+
+varying vec2 texCoords;
+varying vec4 vertexColor;
+
+float aastep(float threshold, float dist) {
+	float afwidth = 0.75 * length(vec2(dFdx(dist), dFdy(dist)));
+	return smoothstep(threshold - afwidth, threshold + afwidth, dist);
+}
+
+float median(float r, float g, float b) {
+	return max(min(r, g), min(max(r, g), b));
+}
+
+const float distanceThreshold = 0.5;
+
+float sample(vec2 tc) {
+	vec3 texel = texture2D(Texture1, tc).rgb;
+	float dist = median(texel.r, texel.g, texel.b);
+	return aastep(distanceThreshold, dist);
+}
+
+void main(void)
+{
+	float dfValue = sample(texCoords);
+	gl_FragColor = vec4(vertexColor.rgb, vertexColor.a * dfValue);
+}
diff --git a/Data/Shaders/GLSL/Distance field.vert b/Data/Shaders/GLSL/Distance field.vert
new file mode 100644
index 0000000000..1d8a59cf10
--- /dev/null
+++ b/Data/Shaders/GLSL/Distance field.vert	
@@ -0,0 +1,10 @@
+//We need this shader to pass the vertex color to the frag shader
+
+varying vec4 vertexColor;
+varying vec2 texCoords;
+
+void main(void) {
+	vertexColor = gl_Color;
+	texCoords = gl_MultiTexCoord0.st;
+	gl_Position = gl_Vertex * gl_ModelViewProjectionMatrix;
+}
diff --git a/src/RageDisplay_OGL.cpp b/src/RageDisplay_OGL.cpp
index cdfffd846d..e136fddc41 100644
--- a/src/RageDisplay_OGL.cpp
+++ b/src/RageDisplay_OGL.cpp
@@ -364,6 +364,8 @@ GLhandleARB LoadShader( GLenum ShaderType, RString sFile, vector<RString> asDefi
 		secondaryShader = CompileShader( GL_FRAGMENT_SHADER_ARB, "Data/Shaders/GLSL/Cel.frag", asDefines);
 	else if (sFile == "Data/Shaders/GLSL/Shell.vert")
 		secondaryShader = CompileShader( GL_FRAGMENT_SHADER_ARB, "Data/Shaders/GLSL/Shell.frag", asDefines);
+	else if (sFile == "Data/Shaders/GLSL/Distance field.vert")
+		secondaryShader = CompileShader( GL_FRAGMENT_SHADER_ARB, "Data/Shaders/GLSL/Distance field.frag", asDefines);
 	
 	GLhandleARB hShader = CompileShader( ShaderType, sFile, asDefines );
 	if (hShader == 0)
@@ -405,6 +407,7 @@ static GLhandleARB g_hScreenShader = 0;
 static GLhandleARB g_hYUYV422Shader = 0;
 static GLhandleARB g_gShellShader = 0;
 static GLhandleARB g_gCelShader = 0;
+static GLhandleARB g_gDistanceFieldShader = 0;
 
 void InitShaders()
 {
@@ -419,6 +422,7 @@ void InitShaders()
 	// these two are for dancing characters and are both actually shader pairs
 	g_gShellShader = LoadShader(			GL_VERTEX_SHADER_ARB, "Data/Shaders/GLSL/Shell.vert", asDefines );
 	g_gCelShader = LoadShader(			GL_VERTEX_SHADER_ARB, "Data/Shaders/GLSL/Cel.vert", asDefines );
+	g_gDistanceFieldShader	= LoadShader( GL_VERTEX_SHADER_ARB, "Data/Shaders/GLSL/Distance field.vert", asDefines );
 	
 	// effects
 	g_bUnpremultiplyShader	= LoadShader(	GL_FRAGMENT_SHADER_ARB, "Data/Shaders/GLSL/Unpremultiply.frag", asDefines );
@@ -1798,6 +1802,8 @@ void RageDisplay_Legacy::SetEffectMode( EffectMode effect )
 		case EffectMode_YUYV422:
 			hShader = g_hYUYV422Shader;
 			break;
+		case EffectMode_DistanceField:
+			hShader = g_gDistanceFieldShader;
 		default:
 			break;
 	}
@@ -1844,6 +1850,8 @@ bool RageDisplay_Legacy::IsEffectModeSupported( EffectMode effect )
 			return g_hScreenShader != 0;
 		case EffectMode_YUYV422:
 			return g_hYUYV422Shader != 0;
+		case EffectMode_DistanceField:
+			return g_gDistanceFieldShader != 0;
 		default:
 			return false;
 	}
diff --git a/src/RageTypes.cpp b/src/RageTypes.cpp
index b554a042e7..8f5477f02c 100644
--- a/src/RageTypes.cpp
+++ b/src/RageTypes.cpp
@@ -183,7 +183,9 @@ static const char *EffectModeNames[] =
 	"Overlay",
 	"Screen",
 
-	"YUYV422"
+	"YUYV422",
+	/* Draws a graphic from a signed distance field. */
+	"DistanceField"
 };
 XToString( EffectMode );
 LuaXType( EffectMode );
diff --git a/src/RageTypes.h b/src/RageTypes.h
index 40af928dc3..c66f635d86 100644
--- a/src/RageTypes.h
+++ b/src/RageTypes.h
@@ -51,6 +51,7 @@ enum EffectMode
 	EffectMode_Overlay,
 	EffectMode_Screen,
 	EffectMode_YUYV422,
+	EffectMode_DistanceField,
 	NUM_EffectMode,
 	EffectMode_Invalid
 };