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stage: Use precomputed constants instead of trigonometric functions

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This should actually ensure that the calculations of the Z translation
for the projection matrix is resolved to "variable * CONSTANT". The
original factors are left in code so it's trivial to revert to the
trigonometric operations if need be, even without reverting this commit.
This commit is contained in:
Emmanuele Bassi 2013-05-03 11:25:23 -07:00
parent d061a47573
commit f92b78781d
1 changed files with 25 additions and 10 deletions
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35
clutter/clutter-stage.c
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@ -3396,6 +3396,8 @@ clutter_stage_ensure_viewport (ClutterStage *stage)
clutter_actor_queue_redraw (CLUTTER_ACTOR (stage)); clutter_actor_queue_redraw (CLUTTER_ACTOR (stage));
} }
# define _DEG_TO_RAD(d) ((d) * ((float) G_PI / 180.0f))
/* This calculates a distance into the view frustum to position the /* This calculates a distance into the view frustum to position the
* stage so there is a decent amount of space to position geometry * stage so there is a decent amount of space to position geometry
* between the stage and the near clipping plane. * between the stage and the near clipping plane.
@ -3508,13 +3510,26 @@ calculate_z_translation (float z_near)
* z_2d = --------------------------- + z_near * z_2d = --------------------------- + z_near
* sin (0.5°) * sin (0.5°)
*/ */
#define _DEG_TO_RAD (G_PI / 180.0)
return z_near * tanf (30.0f * _DEG_TO_RAD) * /* We expect the compiler should boil this down to z_near * CONSTANT
sinf (120.0f * _DEG_TO_RAD) * cosf (30.5f * _DEG_TO_RAD) / * already, but just in case we use precomputed constants
sinf (0.5f * _DEG_TO_RAD) + */
z_near; #if 0
#undef _DEG_TO_RAD # define A tanf (_DEG_TO_RAD (30.f))
/* We expect the compiler should boil this down to z_near * CONSTANT */ # define B sinf (_DEG_TO_RAD (120.f))
# define C cosf (_DEG_TO_RAD (30.5f))
# define D sinf (_DEG_TO_RAD (.5f))
#else
# define A 0.57735025882720947265625f
# define B 0.866025388240814208984375f
# define C 0.86162912845611572265625f
# define D 0.00872653536498546600341796875f
#endif
return z_near
* A * B * C
/ D
+ z_near;
} }
void void
@ -3546,15 +3561,13 @@ _clutter_stage_maybe_setup_viewport (ClutterStage *stage)
perspective.aspect = priv->viewport[2] / priv->viewport[3]; perspective.aspect = priv->viewport[2] / priv->viewport[3];
z_2d = calculate_z_translation (perspective.z_near); z_2d = calculate_z_translation (perspective.z_near);
#define _DEG_TO_RAD (G_PI / 180.0)
/* NB: z_2d is only enough room for 85% of the stage_height between /* NB: z_2d is only enough room for 85% of the stage_height between
* the stage and the z_near plane. For behind the stage plane we * the stage and the z_near plane. For behind the stage plane we
* want a more consistent gap of 10 times the stage_height before * want a more consistent gap of 10 times the stage_height before
* hitting the far plane so we calculate that relative to the final * hitting the far plane so we calculate that relative to the final
* height of the stage plane at the z_2d_distance we got... */ * height of the stage plane at the z_2d_distance we got... */
perspective.z_far = z_2d + perspective.z_far = z_2d +
tanf ((perspective.fovy / 2.0f) * _DEG_TO_RAD) * z_2d * 20.0f; tanf (_DEG_TO_RAD (perspective.fovy / 2.0f)) * z_2d * 20.0f;
#undef _DEG_TO_RAD
clutter_stage_set_perspective_internal (stage, &perspective); clutter_stage_set_perspective_internal (stage, &perspective);
} }
@ -3581,6 +3594,8 @@ _clutter_stage_maybe_setup_viewport (ClutterStage *stage)
} }
} }
#undef _DEG_TO_RAD
/** /**
* clutter_stage_ensure_redraw: * clutter_stage_ensure_redraw:
* @stage: a #ClutterStage * @stage: a #ClutterStage