EPhysics: allow user to configure simulation

Required to fine tunning performance or avoid objects going throught
others.



SVN revision: 74659

legacy/ephysics/src/bin/test_collision_speed.c

@@ -115,7 +115,7 @@ test_collision_speed(void *data __UNUSED__, Evas_Object *obj __UNUSED__, void *e
    speed_data->bt = bt;
 
    sp = elm_spinner_add(speed_data->base.win);
-   elm_spinner_min_max_set(sp, 0, 500);
+   elm_spinner_min_max_set(sp, 0, 300);
    elm_spinner_step_set(sp, 5);
    elm_spinner_value_set(sp, 100);
    elm_object_style_set(sp, "ephysics-test");
@@ -124,6 +124,7 @@ test_collision_speed(void *data __UNUSED__, Evas_Object *obj __UNUSED__, void *e
 
    world = ephysics_world_new();
    ephysics_world_render_geometry_set(world, 50, 40, WIDTH - 100, FLOOR_Y - 40);
+   ephysics_world_simulation_set(world, 1/260.f, 5);
    speed_data->base.world = world;
 
    boundary = ephysics_body_bottom_boundary_add(world);

legacy/ephysics/src/lib/EPhysics.h

@@ -950,6 +950,86 @@ EAPI void ephysics_world_bodies_outside_left_autodel_set(EPhysics_World *world,
  */
 EAPI Eina_Bool ephysics_world_bodies_outside_left_autodel_get(const EPhysics_World *world);
 
+/**
+ * @brief
+ * Set world simulation's fixed time step and max number of sub steps
+ * configuration.
+ *
+ * It's important that time step is always less than
+ * @p max_sub_steps * @p fixed_time_step, otherwise you are losing time.
+ * Mathematically:
+ *
+ * time step < @p max_sub_steps * @p fixed_time_step;
+ *
+ * If you're a using a very large time step
+ * [say, five times the size of the fixed internal time step],
+ * then you must increase the number of max sub steps to compensate for this,
+ * otherwise your simulation is “losing” time.
+ *
+ * The time step may vary. Simulation ticks are called by an animator,
+ * so, by default, time step is @c 1/30 secs. If you're using elementary,
+ * default FPS configuration is 60 fps, i.e. time step is @c 1/60 secs.
+ * You can change that setting a
+ * different time with ecore_animator_frametime_set().
+ *
+ * Also, keep in mind
+ * that if you're using CPU intense calculations maybe this framerate won't
+ * be achieved, so the time step will be bigger. You need to define
+ * what range of frames per secons you need to support and configure
+ * @p max_sub_steps and @p fixed_time_step according to this.
+ *
+ * By decreasing the size of @p fixed_time_step, you are increasing the
+ * “resolution” of the simulation.
+ *
+ * If you are finding that your objects are moving very fast and escaping
+ * from your walls instead of colliding with them, then one way to help fix
+ * this problem is by decreasing @p fixed_time_step. If you do this,
+ * then you will need to increase @p max_sub_steps to ensure the equation
+ * listed above is still satisfied.
+ *
+ * The issue with this is that each internal “tick” takes an amount of
+ * computation. More of them means your CPU will be spending more time on
+ * physics and therefore less time on other stuff. Say you want twice the
+ * resolution, you'll need twice the @p max_sub_steps, which could chew up
+ * twice as much CPU for the same amount of simulation time.
+ *
+ * When you pass @p max_sub_steps > 1, it will interpolate movement for you.
+ * This means that if your @p fixed_time_step is 3 units, and you pass
+ * a timeStep of 4, then it will do exactly one tick, and estimate the
+ * remaining movement by 1/3. This saves you having to do interpolation
+ * yourself, but keep in mind that maxSubSteps needs to be greater than 1.
+ *
+ * By default @p fixed_time_step is 1/60 seconds and @p max_sub_steps is 3.
+ *
+ * @param world The physics world.
+ * @param fixed_time_step size of the internal simulation step, in seconds.
+ * @param max_sub_steps maximum number of steps that simulation is allowed
+ * to take at each simulation tick.
+ *
+ * @note The unit used for time is seconds.
+ *
+ * @see ephysics_world_simulation_get().
+ *
+ * @ingroup EPhysics_World
+ */
+EAPI void ephysics_world_simulation_set(EPhysics_World *world, double fixed_time_step, int max_sub_steps);
+
+/**
+ * @brief
+ * Get world simulation's fixed time step and max number of sub steps
+ * configuration.
+ *
+ * @param world The physics world.
+ * @param fixed_time_step size of the internal simulation step, in seconds.
+ * @param max_sub_steps maximum number of steps that simulation is allowed
+ * to take at each simulation tick.
+ *
+ * @see ephysics_world_simulation_set() for details.
+ *
+ * @ingroup EPhysics_World
+ */
+EAPI void ephysics_world_simulation_get(const EPhysics_World *world, double *fixed_time_step, int *max_sub_steps);
+
 /**
  * @}
  */

legacy/ephysics/src/lib/ephysics_world.cpp

@@ -31,8 +31,10 @@ struct _EPhysics_World {
      Evas_Coord x, y, w, h;
      Eina_Inlist *callbacks;
      Eina_List *bodies;
+     int max_sub_steps;
      double last_update;
      double rate;
+     double fixed_time_step;
      Eina_Bool running:1;
      Eina_Bool active:1;
      Eina_Bool outside_autodel:1;
@@ -141,7 +143,8 @@ _simulate_worlds(void *data)
         world->last_update = time_now;
 
         gDeactivationTime = world->max_sleeping_time;
-        world->dynamics_world->stepSimulation(delta, 1, 1/40.f);
+        world->dynamics_world->stepSimulation(delta, world->max_sub_steps,
+                                              world->fixed_time_step);
      }
 
    return EINA_TRUE;
@@ -342,6 +345,8 @@ ephysics_world_new(void)
      world->dynamics_world->getPairCache()->setOverlapFilterCallback(filter_cb);
 
    world->rate = 30;
+   world->max_sub_steps = 3;
+   world->fixed_time_step = 1/60.f;
    world->dynamics_world->setInternalTickCallback(_ephysics_world_tick_cb,
                                                   (void *) world);
 
@@ -927,7 +932,7 @@ ephysics_world_bodies_outside_right_autodel_get(const EPhysics_World *world)
    return world->outside_right;
 }
 
-Eina_Bool
+EAPI Eina_Bool
 ephysics_world_bodies_outside_autodel_get(const EPhysics_World *world)
 {
    if (!world)
@@ -939,6 +944,47 @@ ephysics_world_bodies_outside_autodel_get(const EPhysics_World *world)
    return world->outside_autodel;
 }
 
+EAPI void
+ephysics_world_simulation_set(EPhysics_World *world, double fixed_time_step, int max_sub_steps)
+{
+   if (!world)
+     {
+        ERR("Can't set simulation, no world provided.");
+        return;
+     }
+
+   if (max_sub_steps < 1)
+     {
+        ERR("At least one sub step for simulation is required.");
+        return;
+     }
+
+   if (ecore_animator_frametime_get() >= max_sub_steps * fixed_time_step)
+     {
+        ERR("Assure frametime < max sub steps * fixed time step.");
+        return;
+     }
+
+   world->max_sub_steps = max_sub_steps;
+   world->fixed_time_step = fixed_time_step;
+
+   DBG("World %p simulation set to fixed time step: %lf, max substeps:%i.",
+       world, fixed_time_step, max_sub_steps);
+}
+
+EAPI void
+ephysics_world_simulation_get(const EPhysics_World *world, double *fixed_time_step, int *max_sub_steps)
+{
+   if (!world)
+     {
+	ERR("No world, can't get simulation configuration.");
+	return;
+     }
+
+   if (fixed_time_step) *fixed_time_step = world->fixed_time_step;
+   if (max_sub_steps) *max_sub_steps = world->max_sub_steps;
+}
+
 #ifdef  __cplusplus
 }
 #endif