[mutter/gbsneto/graphene-matrix: 9/57] cogl/matrix: Project and transpose using graphene matrices

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

commit d76a00632ea56db4213bd2240ea58a4e13e5a6bc
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Thu Sep 10 13:57:41 2020 -0300

    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

 cogl/cogl/cogl-matrix.c | 108 +++++++++++++++++++++++++++++++++---------------
 1 file changed, 74 insertions(+), 34 deletions(-)
---
diff --git a/cogl/cogl/cogl-matrix.c b/cogl/cogl/cogl-matrix.c
index f0be094966..1ba7a8ac10 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
@@ -1704,6 +1710,21 @@ typedef struct _Point4f
   float w;
 } 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,
@@ -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);
     }
 }