cogl/matrix: Project and transpose using graphene matrices

Use dot products to simplify calculations. Because the 'w' column of
the matrix is always summed, use 1.f in the 'w' component of the point
vector.

Because CoglMatrix is column-major and graphene_matrix_t is row-major,
it is necessary to transpose the matrix before retrieving the rows.
When we switch CoglMatrix to be row-major, this transposition will
go away.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1439

1 files changed, 74 insertions, 34 deletions

diff --git a/cogl/cogl/cogl-matrix.c b/cogl/cogl/cogl-matrix.c
index f0be09496..1ba7a8ac1 100644
--- a/cogl/cogl/cogl-matrix.c
+++ b/cogl/cogl/cogl-matrix.c
@@ -1675,12 +1675,18 @@ cogl_matrix_transform_point (const CoglMatrix *matrix,
                              float *z,
                              float *w)
 {
-  float _x = *x, _y = *y, _z = *z, _w = *w;
+  graphene_matrix_t m;
+  graphene_vec4_t p;
+
+  graphene_vec4_init (&p, *x, *y, *z, *w);
+
+  cogl_matrix_to_graphene_matrix (matrix, &m);
+  graphene_matrix_transform_vec4 (&m, &p, &p);
 
-  *x = matrix->xx * _x + matrix->xy * _y + matrix->xz * _z + matrix->xw * _w;
-  *y = matrix->yx * _x + matrix->yy * _y + matrix->yz * _z + matrix->yw * _w;
-  *z = matrix->zx * _x + matrix->zy * _y + matrix->zz * _z + matrix->zw * _w;
-  *w = matrix->wx * _x + matrix->wy * _y + matrix->wz * _z + matrix->ww * _w;
+  *x = graphene_vec4_get_x (&p);
+  *y = graphene_vec4_get_y (&p);
+  *z = graphene_vec4_get_z (&p);
+  *w = graphene_vec4_get_w (&p);
 }
 
 typedef struct _Point2f
@@ -1705,6 +1711,21 @@ typedef struct _Point4f
 } Point4f;
 
 static void
+init_matrix_rows (const CoglMatrix *matrix,
+                  unsigned int      n_rows,
+                  graphene_vec4_t  *rows)
+{
+  graphene_matrix_t m;
+  unsigned int i;
+
+  cogl_matrix_to_graphene_matrix (matrix, &m);
+  graphene_matrix_transpose (&m, &m);
+
+  for (i = 0; i < n_rows; i++)
+    graphene_matrix_get_row (&m, i, &rows[i]);
+}
+
+static void
 _cogl_matrix_transform_points_f2 (const CoglMatrix *matrix,
                                   size_t stride_in,
                                   const void *points_in,
@@ -1712,16 +1733,22 @@ _cogl_matrix_transform_points_f2 (const CoglMatrix *matrix,
                                   void *points_out,
                                   int n_points)
 {
+  graphene_vec4_t rows[3];
   int i;
 
+  init_matrix_rows (matrix, G_N_ELEMENTS (rows), rows);
+
   for (i = 0; i < n_points; i++)
     {
       Point2f p = *(Point2f *)((uint8_t *)points_in + i * stride_in);
       Point3f *o = (Point3f *)((uint8_t *)points_out + i * stride_out);
+      graphene_vec4_t point;
 
-      o->x = matrix->xx * p.x + matrix->xy * p.y + matrix->xw;
-      o->y = matrix->yx * p.x + matrix->yy * p.y + matrix->yw;
-      o->z = matrix->zx * p.x + matrix->zy * p.y + matrix->zw;
+      graphene_vec4_init (&point, p.x, p.y, 0.f, 1.f);
+
+      o->x = graphene_vec4_dot (&rows[0], &point);
+      o->y = graphene_vec4_dot (&rows[1], &point);
+      o->z = graphene_vec4_dot (&rows[2], &point);
     }
 }
 
@@ -1733,17 +1760,23 @@ _cogl_matrix_project_points_f2 (const CoglMatrix *matrix,
                                 void *points_out,
                                 int n_points)
 {
+  graphene_vec4_t rows[4];
   int i;
 
+  init_matrix_rows (matrix, G_N_ELEMENTS (rows), rows);
+
   for (i = 0; i < n_points; i++)
     {
       Point2f p = *(Point2f *)((uint8_t *)points_in + i * stride_in);
       Point4f *o = (Point4f *)((uint8_t *)points_out + i * stride_out);
+      graphene_vec4_t point;
+
+      graphene_vec4_init (&point, p.x, p.y, 0.f, 1.f);
 
-      o->x = matrix->xx * p.x + matrix->xy * p.y + matrix->xw;
-      o->y = matrix->yx * p.x + matrix->yy * p.y + matrix->yw;
-      o->z = matrix->zx * p.x + matrix->zy * p.y + matrix->zw;
-      o->w = matrix->wx * p.x + matrix->wy * p.y + matrix->ww;
+      o->x = graphene_vec4_dot (&rows[0], &point);
+      o->y = graphene_vec4_dot (&rows[1], &point);
+      o->z = graphene_vec4_dot (&rows[2], &point);
+      o->w = graphene_vec4_dot (&rows[3], &point);
     }
 }
 
@@ -1755,19 +1788,22 @@ _cogl_matrix_transform_points_f3 (const CoglMatrix *matrix,
                                   void *points_out,
                                   int n_points)
 {
+  graphene_vec4_t rows[3];
   int i;
 
+  init_matrix_rows (matrix, G_N_ELEMENTS (rows), rows);
+
   for (i = 0; i < n_points; i++)
     {
       Point3f p = *(Point3f *)((uint8_t *)points_in + i * stride_in);
       Point3f *o = (Point3f *)((uint8_t *)points_out + i * stride_out);
+      graphene_vec4_t point;
+
+      graphene_vec4_init (&point, p.x, p.y, p.z, 1.f);
 
-      o->x = matrix->xx * p.x + matrix->xy * p.y +
-             matrix->xz * p.z + matrix->xw;
-      o->y = matrix->yx * p.x + matrix->yy * p.y +
-             matrix->yz * p.z + matrix->yw;
-      o->z = matrix->zx * p.x + matrix->zy * p.y +
-             matrix->zz * p.z + matrix->zw;
+      o->x = graphene_vec4_dot (&rows[0], &point);
+      o->y = graphene_vec4_dot (&rows[1], &point);
+      o->z = graphene_vec4_dot (&rows[2], &point);
     }
 }
 
@@ -1779,21 +1815,23 @@ _cogl_matrix_project_points_f3 (const CoglMatrix *matrix,
                                 void *points_out,
                                 int n_points)
 {
+  graphene_vec4_t rows[4];
   int i;
 
+  init_matrix_rows (matrix, G_N_ELEMENTS (rows), rows);
+
   for (i = 0; i < n_points; i++)
     {
       Point3f p = *(Point3f *)((uint8_t *)points_in + i * stride_in);
       Point4f *o = (Point4f *)((uint8_t *)points_out + i * stride_out);
+      graphene_vec4_t point;
 
-      o->x = matrix->xx * p.x + matrix->xy * p.y +
-             matrix->xz * p.z + matrix->xw;
-      o->y = matrix->yx * p.x + matrix->yy * p.y +
-             matrix->yz * p.z + matrix->yw;
-      o->z = matrix->zx * p.x + matrix->zy * p.y +
-             matrix->zz * p.z + matrix->zw;
-      o->w = matrix->wx * p.x + matrix->wy * p.y +
-             matrix->wz * p.z + matrix->ww;
+      graphene_vec4_init (&point, p.x, p.y, p.z, 1.f);
+
+      o->x = graphene_vec4_dot (&rows[0], &point);
+      o->y = graphene_vec4_dot (&rows[1], &point);
+      o->z = graphene_vec4_dot (&rows[2], &point);
+      o->w = graphene_vec4_dot (&rows[3], &point);
     }
 }
 
@@ -1805,21 +1843,23 @@ _cogl_matrix_project_points_f4 (const CoglMatrix *matrix,
                                 void *points_out,
                                 int n_points)
 {
+  graphene_vec4_t rows[4];
   int i;
 
+  init_matrix_rows (matrix, G_N_ELEMENTS (rows), rows);
+
   for (i = 0; i < n_points; i++)
     {
       Point4f p = *(Point4f *)((uint8_t *)points_in + i * stride_in);
       Point4f *o = (Point4f *)((uint8_t *)points_out + i * stride_out);
+      graphene_vec4_t point;
+
+      graphene_vec4_init (&point, p.x, p.y, p.z, p.w);
 
-      o->x = matrix->xx * p.x + matrix->xy * p.y +
-             matrix->xz * p.z + matrix->xw * p.w;
-      o->y = matrix->yx * p.x + matrix->yy * p.y +
-             matrix->yz * p.z + matrix->yw * p.w;
-      o->z = matrix->zx * p.x + matrix->zy * p.y +
-             matrix->zz * p.z + matrix->zw * p.w;
-      o->w = matrix->wx * p.x + matrix->wy * p.y +
-             matrix->wz * p.z + matrix->ww * p.w;
+      o->x = graphene_vec4_dot (&rows[0], &point);
+      o->y = graphene_vec4_dot (&rows[1], &point);
+      o->z = graphene_vec4_dot (&rows[2], &point);
+      o->w = graphene_vec4_dot (&rows[3], &point);
     }
 }