ephysics: support density

SVN revision: 77460

legacy/ephysics/src/lib/EPhysics.h

@@ -2698,6 +2698,47 @@ EAPI void ephysics_body_forces_clear(EPhysics_Body *body);
  */
 EAPI void ephysics_body_center_mass_get(const EPhysics_Body *body, double *x, double *y);
 
+/**
+ * @brief
+ * Set body's material density.
+ *
+ * The density of a material is its mass per unit volume. It will set the
+ * body mass considering its volume. While a density is set, resizing
+ * a body will always recalculate its mass.
+ *
+ * When a mass is explicitely set with @ref ephysics_body_mass_set(),
+ * the density will be unset.
+ *
+ * It's useful in cases where a specific material needs to be simulated,
+ * so its density can be set and ephysics will calcute the body's mass.
+ *
+ * By default, no density is set.
+ *
+ * @note The unit used for density is kilograms / meters ^ 3.
+ *
+ * @param body The body to has its material density set.
+ * @param density The @p body's material density, in kilograms / meters ^ 3.
+ *
+ * @see ephysics_body_density_get().
+ *
+ * @ingroup EPhysics_Body
+ */
+EAPI void ephysics_body_density_set(EPhysics_Body *body, double density);
+
+/**
+ * @brief
+ * Get body's material density.
+ *
+ * @param body The physics body.
+ * @return the @p body material's density, in kilograms / meters ^ 3 or 0
+ * if no density is set.
+ *
+ * @see ephysics_body_density_set() for details.
+ *
+ * @ingroup EPhysics_Body
+ */
+EAPI double ephysics_body_density_get(const EPhysics_Body *body);
+
 /**
  * @}
  */

legacy/ephysics/src/lib/ephysics_body.cpp

@@ -347,11 +347,21 @@ _ephysics_body_soft_body_constraints_rebuild(EPhysics_Body *body)
    _ephysics_body_soft_body_points_distance_get(body, body->distances);
 }
 
+inline static double
+_ephysics_body_volume_get(const EPhysics_Body *body)
+{
+   btVector3 vector = body->collision_shape->getLocalScaling();
+   return vector.x() * vector.y() * vector.z();
+}
+
 static void
 _ephysics_body_mass_set(EPhysics_Body *body, double mass)
 {
    btVector3 inertia(0, 0, 0);
 
+   if (body->density)
+     mass = body->density * _ephysics_body_volume_get(body);
+
    if (body->soft_body)
      body->soft_body->setTotalMass(mass);
    else
@@ -1408,6 +1418,7 @@ ephysics_body_mass_set(EPhysics_Body *body, double mass)
      }
 
    ephysics_world_lock_take(body->world);
+   body->density = 0;
    _ephysics_body_mass_set(body, mass);
    ephysics_world_lock_release(body->world);
 }
@@ -2012,6 +2023,33 @@ ephysics_body_center_mass_get(const EPhysics_Body *body, double *x, double *y)
    if (y) *y = body->cm.y;
 }
 
+EAPI void
+ephysics_body_density_set(EPhysics_Body *body, double density)
+{
+   if (!body)
+     {
+        ERR("Can't set the density of a null body's material.");
+        return;
+     }
+
+   body->density = density;
+   ephysics_world_lock_take(body->world);
+   _ephysics_body_mass_set(body, 0);
+   ephysics_world_lock_release(body->world);
+}
+
+EAPI double
+ephysics_body_density_get(const EPhysics_Body *body)
+{
+   if (!body)
+     {
+        ERR("Can't get the density of a null body's material.");
+        return 0;
+     }
+
+   return body->density;
+}
+
 #ifdef  __cplusplus
 }
 #endif

legacy/ephysics/src/lib/ephysics_private.h

@@ -80,6 +80,7 @@ struct _EPhysics_Body {
      Eina_List *collision_groups;
      Eina_List *to_delete;
      double mass;
+     double density;
      struct {
           double x;
           double y;