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>

(cherry picked from commit e66d9965897999a4889063f6df9a20ea6abf97fe)

1 files changed, 78 insertions, 0 deletions

diff --git a/cogl/cogl-matrix.c b/cogl/cogl-matrix.c
index 512327f9..d82ca827 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.
  */