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clutter/stage: Simplify view setup

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ClutterStage defines the 8 vertices of a frustum:

  4 ----------------------------- 5
  | \                           / |
  |  \                         /  |
  |   0 --------------------- 1   |
  |   |                       |   |
  |   |                       |   |
  |   3 --------------------- 2   |
  |  /                         \  |
  | /                           \ |
  7 ----------------------------- 6

Then, it uses triplets of vertices to create each  clipping plane.
It only sets up 4 planes (it doesn't clip based on depth), defined
by the following vertices:

 * 0 - 4 - 5
 * 1 - 5 - 6
 * 2 - 6 - 7
 * 0 - 7 - 4

The first 3 triplets are selected using the for-loop. However, the
last triplet is different, and is done out of the loop. It could
have been made simpler by using the "3 - 7 - 4" triplet.

Simplify the current code by using the suggested triplet, calculated
inside the for-loop.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1489
This commit is contained in:
Georges Basile Stavracas Neto 2020-10-09 15:54:18 -03:00
parent 1f99395d20
commit 175851eef7
1 changed files with 2 additions and 20 deletions
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22
clutter/clutter/clutter-stage.c
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@ -674,7 +674,6 @@ _cogl_util_get_eye_planes_for_screen_poly (float *polygon,
graphene_vec3_t b;
graphene_vec3_t c;
float zw, ww;
int count;
tmp_poly = g_alloca (sizeof (Vector4) * n_vertices * 2);
@ -738,8 +737,7 @@ _cogl_util_get_eye_planes_for_screen_poly (float *polygon,
* cogl_vector APIs just took pointers to floats.
*/
count = n_vertices - 1;
for (i = 0; i < count; i++)
for (i = 0; i < n_vertices; i++)
{
plane = &planes[i];
@ -749,7 +747,7 @@ _cogl_util_get_eye_planes_for_screen_poly (float *polygon,
poly = &tmp_poly[n_vertices + i];
graphene_vec3_init (&b, poly->x, poly->y, poly->z);
poly = &tmp_poly[n_vertices + i + 1];
poly = &tmp_poly[n_vertices + ((i + 1) % n_vertices)];
graphene_vec3_init (&c, poly->x, poly->y, poly->z);
graphene_vec3_subtract (&b, &plane->v0, &b);
@ -757,22 +755,6 @@ _cogl_util_get_eye_planes_for_screen_poly (float *polygon,
graphene_vec3_cross (&b, &c, &plane->n);
graphene_vec3_normalize (&plane->n, &plane->n);
}
plane = &planes[n_vertices - 1];
poly = &tmp_poly[0];
graphene_vec3_init (&plane->v0, poly->x, poly->y, poly->z);
poly = &tmp_poly[2 * n_vertices - 1];
graphene_vec3_init (&b, poly->x, poly->y, poly->z);
poly = &tmp_poly[n_vertices];
graphene_vec3_init (&c, poly->x, poly->y, poly->z);
graphene_vec3_subtract (&b, &plane->v0, &b);
graphene_vec3_subtract (&c, &plane->v0, &c);
graphene_vec3_cross (&b, &c, &plane->n);
graphene_vec3_normalize (&plane->n, &plane->n);
}
/* XXX: Instead of having a toplevel 2D clip region, it might be