From b2c8b2238877f76cdea184cca70336b15ddb78d9 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Fri, 28 Oct 2016 19:34:10 +0300
Subject: [PATCH] Refactor TextureCube face information functions with lookup
 tables

---
 source/texturecube.cpp | 76 +++++++++++++++++++++---------------------
 source/texturecube.h   |  4 +++
 2 files changed, 42 insertions(+), 38 deletions(-)

diff --git a/source/texturecube.cpp b/source/texturecube.cpp
index e767423f..833ef28f 100644
--- a/source/texturecube.cpp
+++ b/source/texturecube.cpp
@@ -13,6 +13,16 @@ using namespace std;
 namespace Msp {
 namespace GL {
 
+TextureCubeFace TextureCube::face_order[6] =
+{
+	POSITIVE_X,
+	NEGATIVE_X,
+	POSITIVE_Y,
+	NEGATIVE_Y,
+	POSITIVE_Z,
+	NEGATIVE_Z
+};
+
 Vector3 TextureCube::directions[6] =
 {
 	Vector3(1, 0, 0),
@@ -23,6 +33,16 @@ Vector3 TextureCube::directions[6] =
 	Vector3(0, 0, -1)
 };
 
+unsigned TextureCube::orientations[12] =
+{
+	5, 3,
+	4, 3,
+	0, 4,
+	0, 5,
+	0, 3,
+	1, 3
+};
+
 TextureCube::TextureCube():
 	Texture(GL_TEXTURE_CUBE_MAP),
 	ifmt(RGB),
@@ -166,58 +186,38 @@ unsigned TextureCube::get_level_size(unsigned level) const
 
 TextureCubeFace TextureCube::enumerate_faces(unsigned i)
 {
-	switch(i)
-	{
-	case 0: return POSITIVE_X;
-	case 1: return NEGATIVE_X;
-	case 2: return POSITIVE_Y;
-	case 3: return NEGATIVE_Y;
-	case 4: return POSITIVE_Z;
-	case 5: return NEGATIVE_Z;
-	default: throw out_of_range("TextureCube::enumerate_faces");
-	}
+	if(i>=6)
+		throw out_of_range("TextureCube::enumerate_faces");
+	return face_order[i];
 }
 
-const Vector3 &TextureCube::get_face_direction(TextureCubeFace face)
+unsigned TextureCube::get_face_index(TextureCubeFace face)
 {
 	switch(face)
 	{
-	case POSITIVE_X: return directions[0];
-	case NEGATIVE_X: return directions[1];
-	case POSITIVE_Y: return directions[2];
-	case NEGATIVE_Y: return directions[3];
-	case POSITIVE_Z: return directions[4];
-	case NEGATIVE_Z: return directions[5];
-	default: throw invalid_argument("TextureCube::get_face_direction");
+	case POSITIVE_X: return 0;
+	case NEGATIVE_X: return 1;
+	case POSITIVE_Y: return 2;
+	case NEGATIVE_Y: return 3;
+	case POSITIVE_Z: return 4;
+	case NEGATIVE_Z: return 5;
+	default: throw invalid_argument("TextureCube::get_face_index");
 	}
 }
 
+const Vector3 &TextureCube::get_face_direction(TextureCubeFace face)
+{
+	return directions[get_face_index(face)];
+}
+
 const Vector3 &TextureCube::get_s_direction(TextureCubeFace face)
 {
-	switch(face)
-	{
-	case POSITIVE_X: return directions[5];
-	case NEGATIVE_X: return directions[4];
-	case POSITIVE_Y: return directions[0];
-	case NEGATIVE_Y: return directions[0];
-	case POSITIVE_Z: return directions[0];
-	case NEGATIVE_Z: return directions[1];
-	default: throw invalid_argument("TextureCube::get_s_direction");
-	}
+	return directions[orientations[get_face_index(face)*2]];
 }
 
 const Vector3 &TextureCube::get_t_direction(TextureCubeFace face)
 {
-	switch(face)
-	{
-	case POSITIVE_X: return directions[3];
-	case NEGATIVE_X: return directions[3];
-	case POSITIVE_Y: return directions[4];
-	case NEGATIVE_Y: return directions[5];
-	case POSITIVE_Z: return directions[3];
-	case NEGATIVE_Z: return directions[3];
-	default: throw invalid_argument("TextureCube::get_t_direction");
-	}
+	return directions[orientations[get_face_index(face)*2+1]];
 }
 
 Vector3 TextureCube::get_texel_direction(TextureCubeFace face, unsigned u, unsigned v)
diff --git a/source/texturecube.h b/source/texturecube.h
index 62f1189a..9ce216fd 100644
--- a/source/texturecube.h
+++ b/source/texturecube.h
@@ -53,7 +53,9 @@ private:
 	unsigned size;
 	unsigned allocated;
 
+	static TextureCubeFace face_order[6];
 	static Vector3 directions[6];
+	static unsigned orientations[12];
 
 public:
 	TextureCube();
@@ -93,6 +95,8 @@ public:
 	and 5, inclusive. */
 	static TextureCubeFace enumerate_faces(unsigned);
 
+	static unsigned get_face_index(TextureCubeFace);
+
 	/** Returns a vector pointing out of the face. */
 	static const Vector3 &get_face_direction(TextureCubeFace);
 
-- 
2.45.2