[mutter/gbsneto/graphene-matrix: 2/57] cogl/matrix: Rotate using graphene matrices

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 30c94f29a05c8ad8b46ca8634766671319714f34
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Thu Sep 10 10:40:33 2020 -0300

    cogl/matrix: Rotate using graphene matrices
    
    This is pretty similar to the other conversions, except we need to
    store the matrix flags before operating on it, and update it using
    this old value after. That's because cogl_matrix_init_from_array()
    marks the matrix as entirely dirty, and we don't want that.
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1439

 cogl/cogl/cogl-matrix.c | 212 ++++--------------------------------------------
 1 file changed, 16 insertions(+), 196 deletions(-)
---
diff --git a/cogl/cogl/cogl-matrix.c b/cogl/cogl/cogl-matrix.c
index d191bed9e9..25858c7d0b 100644
--- a/cogl/cogl/cogl-matrix.c
+++ b/cogl/cogl/cogl-matrix.c
@@ -1155,201 +1155,6 @@ cogl_matrix_get_inverse (const CoglMatrix *matrix, CoglMatrix *inverse)
     }
 }
 
-/*
- * Generate a 4x4 transformation matrix from glRotate parameters, and
- * post-multiply the input matrix by it.
- *
- * \author
- * This function was contributed by Erich Boleyn (erich uruk org).
- * Optimizations contributed by Rudolf Opalla (rudi khm de).
- */
-static void
-_cogl_matrix_rotate (CoglMatrix *matrix,
-                     float angle,
-                     float x,
-                     float y,
-                     float z)
-{
-  float xx, yy, zz, xy, yz, zx, xs, ys, zs, one_c, s, c;
-  float m[16];
-  gboolean optimized;
-
-  s = sinf (angle * DEG2RAD);
-  c = cosf (angle * DEG2RAD);
-
-  memcpy (m, identity, 16 * sizeof (float));
-  optimized = FALSE;
-
-#define M(row,col)  m[col*4+row]
-
-  if (x == 0.0f)
-    {
-      if (y == 0.0f)
-        {
-          if (z != 0.0f)
-            {
-              optimized = TRUE;
-              /* rotate only around z-axis */
-              M (0,0) = c;
-              M (1,1) = c;
-              if (z < 0.0f)
-                {
-                  M (0,1) = s;
-                  M (1,0) = -s;
-                }
-              else
-                {
-                  M (0,1) = -s;
-                  M (1,0) = s;
-                }
-            }
-        }
-      else if (z == 0.0f)
-        {
-          optimized = TRUE;
-          /* rotate only around y-axis */
-          M (0,0) = c;
-          M (2,2) = c;
-          if (y < 0.0f)
-            {
-              M (0,2) = -s;
-              M (2,0) = s;
-            }
-          else
-            {
-              M (0,2) = s;
-              M (2,0) = -s;
-            }
-        }
-    }
-  else if (y == 0.0f)
-    {
-      if (z == 0.0f)
-        {
-          optimized = TRUE;
-          /* rotate only around x-axis */
-          M (1,1) = c;
-          M (2,2) = c;
-          if (x < 0.0f)
-            {
-              M (1,2) = s;
-              M (2,1) = -s;
-            }
-          else
-            {
-              M (1,2) = -s;
-              M (2,1) = s;
-            }
-        }
-    }
-
-  if (!optimized)
-    {
-      const float mag = sqrtf (x * x + y * y + z * z);
-
-      if (mag <= 1.0e-4)
-        {
-          /* no rotation, leave mat as-is */
-          return;
-        }
-
-      x /= mag;
-      y /= mag;
-      z /= mag;
-
-
-      /*
-       *     Arbitrary axis rotation matrix.
-       *
-       *  This is composed of 5 matrices, Rz, Ry, T, Ry', Rz', multiplied
-       *  like so:  Rz * Ry * T * Ry' * Rz'.  T is the final rotation
-       *  (which is about the X-axis), and the two composite transforms
-       *  Ry' * Rz' and Rz * Ry are (respectively) the rotations necessary
-       *  from the arbitrary axis to the X-axis then back.  They are
-       *  all elementary rotations.
-       *
-       *  Rz' is a rotation about the Z-axis, to bring the axis vector
-       *  into the x-z plane.  Then Ry' is applied, rotating about the
-       *  Y-axis to bring the axis vector parallel with the X-axis.  The
-       *  rotation about the X-axis is then performed.  Ry and Rz are
-       *  simply the respective inverse transforms to bring the arbitrary
-       *  axis back to it's original orientation.  The first transforms
-       *  Rz' and Ry' are considered inverses, since the data from the
-       *  arbitrary axis gives you info on how to get to it, not how
-       *  to get away from it, and an inverse must be applied.
-       *
-       *  The basic calculation used is to recognize that the arbitrary
-       *  axis vector (x, y, z), since it is of unit length, actually
-       *  represents the sines and cosines of the angles to rotate the
-       *  X-axis to the same orientation, with theta being the angle about
-       *  Z and phi the angle about Y (in the order described above)
-       *  as follows:
-       *
-       *  cos ( theta ) = x / sqrt ( 1 - z^2 )
-       *  sin ( theta ) = y / sqrt ( 1 - z^2 )
-       *
-       *  cos ( phi ) = sqrt ( 1 - z^2 )
-       *  sin ( phi ) = z
-       *
-       *  Note that cos ( phi ) can further be inserted to the above
-       *  formulas:
-       *
-       *  cos ( theta ) = x / cos ( phi )
-       *  sin ( theta ) = y / sin ( phi )
-       *
-       *  ...etc.  Because of those relations and the standard trigonometric
-       *  relations, it is pssible to reduce the transforms down to what
-       *  is used below.  It may be that any primary axis chosen will give the
-       *  same results (modulo a sign convention) using this method.
-       *
-       *  Particularly nice is to notice that all divisions that might
-       *  have caused trouble when parallel to certain planes or
-       *  axis go away with care paid to reducing the expressions.
-       *  After checking, it does perform correctly under all cases, since
-       *  in all the cases of division where the denominator would have
-       *  been zero, the numerator would have been zero as well, giving
-       *  the expected result.
-       */
-
-      xx = x * x;
-      yy = y * y;
-      zz = z * z;
-      xy = x * y;
-      yz = y * z;
-      zx = z * x;
-      xs = x * s;
-      ys = y * s;
-      zs = z * s;
-      one_c = 1.0f - c;
-
-      /* We already hold the identity-matrix so we can skip some statements */
-      M (0,0) = (one_c * xx) + c;
-      M (0,1) = (one_c * xy) - zs;
-      M (0,2) = (one_c * zx) + ys;
-      /*    M (0,3) = 0.0f; */
-
-      M (1,0) = (one_c * xy) + zs;
-      M (1,1) = (one_c * yy) + c;
-      M (1,2) = (one_c * yz) - xs;
-      /*    M (1,3) = 0.0f; */
-
-      M (2,0) = (one_c * zx) - ys;
-      M (2,1) = (one_c * yz) + xs;
-      M (2,2) = (one_c * zz) + c;
-      /*    M (2,3) = 0.0f; */
-
-      /*
-         M (3,0) = 0.0f;
-         M (3,1) = 0.0f;
-         M (3,2) = 0.0f;
-         M (3,3) = 1.0f;
-         */
-    }
-#undef M
-
-  matrix_multiply_array_with_flags (matrix, m, MAT_FLAG_ROTATION);
-}
-
 void
 cogl_matrix_rotate (CoglMatrix *matrix,
                    float angle,
@@ -1357,7 +1162,22 @@ cogl_matrix_rotate (CoglMatrix *matrix,
                    float y,
                    float z)
 {
-  _cogl_matrix_rotate (matrix, angle, x, y, z);
+  graphene_matrix_t rotation;
+  graphene_matrix_t m;
+  graphene_vec3_t axis;
+  unsigned long flags;
+
+  flags = matrix->flags;
+
+  cogl_matrix_to_graphene_matrix (matrix, &m);
+  graphene_vec3_init (&axis, x, y, z);
+  graphene_matrix_init_rotate (&rotation, angle, &axis);
+  graphene_matrix_multiply (&rotation, &m, &m);
+  graphene_matrix_to_cogl_matrix (&m, matrix);
+
+  flags |= MAT_FLAG_ROTATION | MAT_DIRTY_TYPE | MAT_DIRTY_INVERSE;
+  matrix->flags = flags;
+
   _COGL_MATRIX_DEBUG_PRINT (matrix);
 }