From 3cdc195408626066c033868a68a3f50a3d9c6e95 Mon Sep 17 00:00:00 2001
From: Tomas Frydrych <tf@openedhand.com>
Date: Tue, 26 Jun 2007 16:07:14 +0000
Subject: [PATCH] tweaked z_camera constant for default 60 deg perspective
 angle

---
 gl/cogl.c   | 30 +++++++++++++++++++++++++-----
 gles/cogl.c | 21 ++++++++++++++++-----
 2 files changed, 41 insertions(+), 10 deletions(-)

diff --git a/gl/cogl.c b/gl/cogl.c
index d99649917..c8a3cda29 100644
--- a/gl/cogl.c
+++ b/gl/cogl.c
@@ -494,7 +494,6 @@ cogl_setup_viewport (guint        width,
 		     ClutterFixed z_far)
 {
   GLfloat z_camera;
-  ClutterFixed fovy_rad = CFX_MUL (fovy, CFX_PI) / 180;
   
   GE( glViewport (0, 0, width, height) );
   
@@ -506,10 +505,31 @@ cogl_setup_viewport (guint        width,
   GE( glMatrixMode (GL_MODELVIEW) );
   GE( glLoadIdentity () );
 
-  /* camera distance from screen, 0.5 * tan (FOV) */
-#define DEFAULT_Z_CAMERA 0.866025404f
-  z_camera = CLUTTER_FIXED_TO_FLOAT (CFX_DIV (clutter_sinx (fovy_rad),
-					      clutter_cosx (fovy_rad)) >> 1);
+  /*
+   * camera distance from screen, 0.5 * tan (FOV)
+   *
+   * We have been having some problems with this; the theoretically correct
+   * value of 0.866025404f for the default 60 deg fovy angle happens to be
+   * touch to small in reality, which on full-screen stage with an actor of
+   * the same size results in about 1px on the left and top edges of the
+   * actor being offscreen. Perhaps more significantly, it also causes
+   * hinting artifacts when rendering text.
+   *
+   * So for the default 60 deg angle we worked out that the value of 0.8699
+   * is giving correct stretch and no noticeable artifacts on text.
+   */
+#define DEFAULT_Z_CAMERA 0.8699f
+  z_camera = DEFAULT_Z_CAMERA;
+
+  if (fovy != CFX_60)
+  {
+    ClutterFixed fovy_rad = CFX_MUL (fovy, CFX_PI) / 180;
+
+    z_camera =
+      CLUTTER_FIXED_TO_FLOAT (CFX_DIV (clutter_sinx (fovy_rad),
+				       clutter_cosx (fovy_rad)) >> 1);
+  }
+  
   GE( glTranslatef (-0.5f, -0.5f, -z_camera) );
   GE( glScalef ( 1.0f / width, 
  	    -1.0f / height, 
diff --git a/gles/cogl.c b/gles/cogl.c
index b279df59e..3fb1631aa 100644
--- a/gles/cogl.c
+++ b/gles/cogl.c
@@ -502,7 +502,6 @@ cogl_setup_viewport (guint        w,
   gint width = (gint) w;
   gint height = (gint) h;
   ClutterFixed z_camera;
-  ClutterFixed fovy_rad = CFX_MUL (fovy, CFX_PI) / 180;
   
   GE( glViewport (0, 0, width, height) );
   GE( glMatrixMode (GL_PROJECTION) );
@@ -517,10 +516,22 @@ cogl_setup_viewport (guint        w,
   GE( glMatrixMode (GL_MODELVIEW) );
   GE( glLoadIdentity () );
 
-  /* camera distance from screen, 0.5 * tan (FOV) */
-#define DEFAULT_Z_CAMERA 0.866025404f
-  z_camera = CFX_DIV (clutter_sinx (fovy_rad),
-		      clutter_cosx (fovy_rad)) >> 1;
+  /*
+   * camera distance from screen, 0.5 * tan (FOV)
+   *
+   * See comments in ../gl/cogl.c
+   */
+#define DEFAULT_Z_CAMERA 0.8699f
+  z_camera = CLUTTER_FLOAT_TO_FIXED (DEFAULT_Z_CAMERA);
+
+  if (fovy != CFX_60)
+  {
+    ClutterFixed fovy_rad = CFX_MUL (fovy, CFX_PI) / 180;
+  
+    z_camera = CFX_DIV (clutter_sinx (fovy_rad),
+			clutter_cosx (fovy_rad)) >> 1;
+  }
+  
 
   GE( glTranslatex (-1 << 15, -1 << 15, -z_camera));