EPhysics: soft body drag coefficient

Add API for handling with soft body drag coefficient.

--This line, and those below, will be ignored--


SVN revision: 80249

legacy/ephysics/src/bin/test_flip_page.c

@@ -163,6 +163,7 @@ _page_add(Test_Data *test_data, EPhysics_Body *anchor, const char *img, Evas_Coo
    evas_object_geometry_get(evas_obj, &page_data->x, NULL, NULL, NULL);
 
    body = ephysics_body_cloth_add(test_data->world, 10, 20);
+   ephysics_body_soft_body_drag_coefficient_set(body, 0.0008);
    ephysics_body_soft_body_position_iterations_set(body, 6);
    ephysics_body_soft_body_bending_constraints_add(body, 1);
    ephysics_body_restitution_set(body, 0);

legacy/ephysics/src/lib/EPhysics.h

@@ -2370,6 +2370,53 @@ EAPI void ephysics_body_soft_body_anchor_hardness_set(EPhysics_Body *body, doubl
  */
 EAPI double ephysics_body_soft_body_anchor_hardness_get(EPhysics_Body *body);
 
+/**
+ * @brief
+ * Set the drag coefficient of a soft body.
+ *
+ * Drag coefficient is a dimensionless quantity used to quantify an objects drag
+ * or resistance in the environment - like air or water resistance. It is used in
+ * the drag equation, where a lower drag coefficient indicates the object will
+ * have less aerodynamic or hydrodynamic drag.
+ *
+ * The drag coefficient is defined as:
+ *
+ * cd = 2Fd / (pv ^ 2)A
+ *
+ * Where:
+ *
+ * - @c Fd is the drag force, which is by definition the force component in the
+ * direction of the flow velocity;
+ * - @c p is the mass density;
+ * - @c v is the speed;
+ * - @c A is the reference area;
+ *
+ * The reference area depends on what type of drag coefficient is being measured.
+ *
+ * @note default value set to 0.
+ *
+ * @param body The body to be set.
+ * @param coefficient  The drag coefficient.
+ *
+ * @see ephysics_body_soft_body_drag_coefficient_get().
+ *
+ * @ingroup EPhysics_Body
+ */
+EAPI void ephysics_body_soft_body_drag_coefficient_set(EPhysics_Body *body, double coefficient);
+
+/**
+ * @brief
+ * Get the drag coefficient of a soft body.
+ *
+ * @param body The body to get the drag coefficient from.
+ * @return The drag coefficient set to @p body on success, -1 on failure.
+ *
+ * @see ephysics_body_soft_body_drag_coefficient_set().
+ *
+ * @ingroup EPhysics_Body
+ */
+EAPI double ephysics_body_soft_body_drag_coefficient_get(const EPhysics_Body *body);
+
 /**
  * @brief
  * Set the soft body dragging status.

legacy/ephysics/src/lib/ephysics_body.cpp

@@ -1806,6 +1806,45 @@ ephysics_body_soft_body_anchor_hardness_get(EPhysics_Body *body)
    return body->soft_body->m_cfg.kAHR * 100;
 }
 
+EAPI void
+ephysics_body_soft_body_drag_coefficient_set(EPhysics_Body *body, double coefficient)
+{
+   if (!body)
+     {
+        ERR("Can't set soft body's drag coefficient, body is null.");
+        return;
+     }
+
+   if (!body->soft_body)
+     {
+        ERR("Can't set soft body's drag coefficient, body seems not to be a soft"
+            " body.");
+        return;
+     }
+
+   body->soft_body->m_cfg.kDG = coefficient;
+   DBG("Soft body drag coefficient set to: %lf", coefficient);
+}
+
+EAPI double
+ephysics_body_soft_body_drag_coefficient_get(const EPhysics_Body *body)
+{
+   if (!body)
+     {
+        ERR("Can't get soft body's drag coefficient, body is null.");
+        return -1;
+     }
+
+   if (!body->soft_body)
+     {
+        ERR("Can't get soft body's drag coefficient, body seems not to be a soft"
+            " body.");
+        return -1;
+     }
+
+   return body->soft_body->m_cfg.kDG;
+}
+
 static void
 _ephysics_body_soft_body_hardness_set(EPhysics_Body *body, double hardness)
 {