[cogl] Add a cogl_matrix_init_from_euler function

[Neil Roberts <nroberts src gnome org>]

commit e66d9965897999a4889063f6df9a20ea6abf97fe
Author: Neil Roberts <neil linux intel com>
Date:   Thu May 17 19:18:58 2012 +0100

    Add a cogl_matrix_init_from_euler function
    
    This creates a matrix to represent the given euler rotation. This
    should be more efficient than creating the matrix by doing three
    separate rotations because no separate intermediate matrices are
    created and no matrix multiplication is needed.
    
    Reviewed-by: Robert Bragg <robert linux intel com>

 cogl/cogl-matrix.c                     |   78 ++++++++++++++++++++++++++++++++
 cogl/cogl-matrix.h                     |   11 +++++
 doc/reference/cogl2/cogl2-sections.txt |    2 +
 3 files changed, 91 insertions(+), 0 deletions(-)
---
diff --git a/cogl/cogl-matrix.c b/cogl/cogl-matrix.c
index 154203a..b9b72ee 100644
--- a/cogl/cogl-matrix.c
+++ b/cogl/cogl-matrix.c
@@ -1751,6 +1751,84 @@ cogl_matrix_init_from_quaternion (CoglMatrix *matrix,
   _cogl_matrix_init_from_quaternion (matrix, quaternion);
 }
 
+void
+cogl_matrix_init_from_euler (CoglMatrix *matrix,
+                             const CoglEuler *euler)
+{
+  /* Convert angles to radians */
+  float heading_rad = euler->heading / 180.0f * G_PI;
+  float pitch_rad = euler->pitch / 180.0f * G_PI;
+  float roll_rad = euler->roll / 180.0f * G_PI;
+  /* Pre-calculate the sin and cos */
+  float sin_heading = sinf (heading_rad);
+  float cos_heading = cosf (heading_rad);
+  float sin_pitch = sinf (pitch_rad);
+  float cos_pitch = cosf (pitch_rad);
+  float sin_roll = sinf (roll_rad);
+  float cos_roll = cosf (roll_rad);
+
+  /* These calculations are based on the following website but they
+   * use a different order for the rotations so it has been modified
+   * slightly.
+   * http://www.euclideanspace.com/maths/geometry/
+   *        rotations/conversions/eulerToMatrix/index.htm
+   */
+
+  /* Heading rotation x=0, y=1, z=0 gives:
+   *
+   * [ ch   0   sh   0 ]
+   * [ 0    1   0    0 ]
+   * [ -sh  0   ch   0 ]
+   * [ 0    0   0    1 ]
+   *
+   * Pitch rotation x=1, y=0, z=0 gives:
+   * [ 1    0   0    0 ]
+   * [ 0    cp  -sp  0 ]
+   * [ 0    sp  cp   0 ]
+   * [ 0    0   0    1 ]
+   *
+   * Roll rotation x=0, y=0, z=1 gives:
+   * [ cr   -sr 0    0 ]
+   * [ sr   cr  0    0 ]
+   * [ 0    0   1    0 ]
+   * [ 0    0   0    1 ]
+   *
+   * Heading matrix * pitch matrix =
+   * [ ch   sh*sp    cp*sh   0  ]
+   * [ 0    cp       -sp     0  ]
+   * [ -sh  ch*sp    ch*cp   0  ]
+   * [ 0    0        0       1  ]
+   *
+   * That matrix * roll matrix =
+   * [ ch*cr + sh*sp*sr   sh*sp*cr - ch*sr       sh*cp       0 ]
+   * [     cp*sr                cp*cr             -sp        0 ]
+   * [ ch*sp*sr - sh*cr   sh*sr + ch*sp*cr       ch*cp       0 ]
+   * [       0                    0                0         1 ]
+   */
+
+  matrix->xx = cos_heading * cos_roll + sin_heading * sin_pitch * sin_roll;
+  matrix->yx = cos_pitch * sin_roll;
+  matrix->zx = cos_heading * sin_pitch * sin_roll - sin_heading * cos_roll;
+  matrix->wx = 0.0f;
+
+  matrix->xy = sin_heading * sin_pitch * cos_roll - cos_heading * sin_roll;
+  matrix->yy = cos_pitch * cos_roll;
+  matrix->zy = sin_heading * sin_roll + cos_heading * sin_pitch * cos_roll;
+  matrix->wy = 0.0f;
+
+  matrix->xz = sin_heading * cos_pitch;
+  matrix->yz = -sin_pitch;
+  matrix->zz = cos_heading * cos_pitch;
+  matrix->wz = 0;
+
+  matrix->xw = 0;
+  matrix->yw = 0;
+  matrix->zw = 0;
+  matrix->ww = 1;
+
+  matrix->flags = (MAT_FLAG_GENERAL | MAT_DIRTY_ALL);
+}
+
 /*
  * Transpose a float matrix.
  */
diff --git a/cogl/cogl-matrix.h b/cogl/cogl-matrix.h
index 0c3d31c..10d0d8a 100644
--- a/cogl/cogl-matrix.h
+++ b/cogl/cogl-matrix.h
@@ -491,6 +491,17 @@ cogl_matrix_get_array (const CoglMatrix *matrix);
 void
 cogl_matrix_init_from_quaternion (CoglMatrix *matrix,
                                   const CoglQuaternion *quaternion);
+
+/**
+ * cogl_matrix_init_from_euler:
+ * @matrix: A 4x4 transformation matrix
+ * @euler: A #CoglEuler
+ *
+ * Initializes @matrix from a #CoglEuler rotation.
+ */
+void
+cogl_matrix_init_from_euler (CoglMatrix *matrix,
+                             const CoglEuler *euler);
 #endif
 
 /**
diff --git a/doc/reference/cogl2/cogl2-sections.txt b/doc/reference/cogl2/cogl2-sections.txt
index 01d2d63..7223334 100644
--- a/doc/reference/cogl2/cogl2-sections.txt
+++ b/doc/reference/cogl2/cogl2-sections.txt
@@ -498,6 +498,8 @@ CoglMatrix
 cogl_matrix_init_identity
 cogl_matrix_init_from_array
 cogl_matrix_init_translation
+cogl_matrix_init_from_quaternion
+cogl_matrix_init_from_euler
 cogl_matrix_copy
 cogl_matrix_equal
 cogl_matrix_free