From 88785e36f6c3bc876deebebd81a26c0198f85479 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Fri, 13 Sep 2013 16:26:44 +0300
Subject: [PATCH] Compensate for chromatic aberration in the Oculus Rift
 combiner

---
 source/oculusriftcombiner.cpp | 39 ++++++++++++++++++++++++++++-------
 source/oculusriftcombiner.h   |  3 +++
 2 files changed, 35 insertions(+), 7 deletions(-)

diff --git a/source/oculusriftcombiner.cpp b/source/oculusriftcombiner.cpp
index 771f3b8..6d5ebf1 100644
--- a/source/oculusriftcombiner.cpp
+++ b/source/oculusriftcombiner.cpp
@@ -21,21 +21,23 @@ const char vs_source[] =
 const char fs_source[] =
 	"uniform sampler2D texture;\n"
 	"uniform vec4 distortion;\n"
+	"uniform vec4 chromatic;\n"
 	"uniform vec2 eye_center;\n"
 	"uniform vec3 scale;\n"
 	"varying vec2 texcoord;\n"
-	"vec2 distort(vec2 coord)\n"
-	"{\n"
-	"	float r_sq = dot(coord, coord);\n"
-	"	return coord*dot(distortion, vec4(1.0, r_sq, r_sq*r_sq, r_sq*r_sq*r_sq));\n"
-	"}\n"
 	"void main()\n"
 	"{\n"
-	"	vec2 dtc = (distort(texcoord)-eye_center)/(scale.xy*scale.z)+0.5;\n"
+	"	float r_sq = dot(texcoord, texcoord);\n"
+	"	float f = dot(distortion, vec4(1.0, r_sq, r_sq*r_sq, r_sq*r_sq*r_sq));\n"
+	"	vec2 dtc = (texcoord*f-eye_center)/(scale.xy*scale.z)+0.5;\n"
 	"	if(dtc.x<0.0 || dtc.y<0.0 || dtc.x>1.0 || dtc.y>1.0)\n"
 	"		gl_FragColor = vec4(0.0);\n"
 	"	else\n"
-	"		gl_FragColor = texture2D(texture, dtc);\n"
+	"	{\n"
+	"		vec2 red_dtc = (texcoord*f*(chromatic[0]+chromatic[1]*r_sq)-eye_center)/(scale.xy*scale.z)+0.5;\n"
+	"		vec2 blue_dtc = (texcoord*f*(chromatic[2]+chromatic[3]*r_sq)-eye_center)/(scale.xy*scale.z)+0.5;\n"
+	"		gl_FragColor = vec4(texture2D(texture, red_dtc).r, texture2D(texture, dtc).g, texture2D(texture, blue_dtc).b, 1.0);\n"
+	"	}\n"
 	"}\n";
 
 }
@@ -59,6 +61,11 @@ OculusRiftCombiner::OculusRiftCombiner():
 	right_shdata.uniform("texture", 0);
 	right_shdata.uniform("offset", 0.5f);
 
+	chromatic[0] = 1.0f;
+	chromatic[1] = 0.0f;
+	chromatic[2] = 1.0f;
+	chromatic[3] = 0.0f;
+
 	// This will also call update_parameters
 	set_distortion(1.0f, 0.22f, 0.24f);
 
@@ -99,6 +106,22 @@ void OculusRiftCombiner::set_distortion(float d0, float d1, float d2, float d3)
 	update_parameters();
 }
 
+void OculusRiftCombiner::set_red_aberration(float c0, float c1)
+{
+	chromatic[0] = c0;
+	chromatic[1] = c1;
+
+	update_parameters();
+}
+
+void OculusRiftCombiner::set_blue_aberration(float c2, float c3)
+{
+	chromatic[2] = c2;
+	chromatic[3] = c3;
+
+	update_parameters();
+}
+
 void OculusRiftCombiner::set_fill_factor(float f)
 {
 	fill_factor = f;
@@ -108,7 +131,9 @@ void OculusRiftCombiner::set_fill_factor(float f)
 void OculusRiftCombiner::update_parameters()
 {
 	left_shdata.uniform4("distortion", distortion);
+	left_shdata.uniform4("chromatic", chromatic);
 	right_shdata.uniform4("distortion", distortion);
+	right_shdata.uniform4("chromatic", chromatic);
 
 	// Set lens center positions, in output texture coordinates
 	left_shdata.uniform("lens_center", 1.0f-lens_separation, 0.5);
diff --git a/source/oculusriftcombiner.h b/source/oculusriftcombiner.h
index a204c3e..afb5573 100644
--- a/source/oculusriftcombiner.h
+++ b/source/oculusriftcombiner.h
@@ -24,6 +24,7 @@ private:
 	float lens_separation;
 	float eye_separation;
 	float distortion[4];
+	float chromatic[4];
 	float fill_factor;
 
 public:
@@ -33,6 +34,8 @@ public:
 	void set_lens_separation(float);
 	void set_eye_separation(float);
 	void set_distortion(float = 1.0f, float = 0.0f, float = 0.0f, float = 0.0f);
+	void set_red_aberration(float = 1.0f, float = 0.0f);
+	void set_blue_aberration(float = 1.0f, float = 0.0f);
 	void set_fill_factor(float);
 private:
 	void update_parameters();
-- 
2.43.0