ephysics: support back-face culling

SVN revision: 78265

legacy/ephysics/src/lib/EPhysics.h

@@ -3641,6 +3641,68 @@ EAPI void ephysics_body_light_set(EPhysics_Body *body, Eina_Bool enable);
  */
 EAPI Eina_Bool ephysics_body_light_get(const EPhysics_Body *body);
 
+/**
+ * @brief
+ * Set body's evas object to be hidden when it is counter-clockwise.
+ *
+ * @param body The physics body.
+ * @param enable If @c EINA_TRUE, evas object will be hidden,
+ * otherwise it will be visible, rotated.
+ *
+ * An object is said to be facing the user when all its points are placed in
+ * a clockwise fashion.
+ *
+ * @note When back-face culling is enabled, evas object visibility
+ * will be handled by @ref ephysics_body_evas_object_update().
+ *
+ * @see ephysics_body_back_face_culling_get().
+ * @see ephysics_body_clockwise_get().
+ * @see ephysics_body_evas_object_set().
+ *
+ * @ingroup EPhysics_Body
+ */
+EAPI void ephysics_body_back_face_culling_set(EPhysics_Body *body, Eina_Bool enable);
+
+/**
+ * @brief
+ * Return if body's evas object will be hidden when it is counter-clockwise or
+ * not.
+ *
+ * @param body The physics body.
+ * @return @c EINA_TRUE if evas object will be hidden, or @c EINA_FALSE
+ * in the other case, or on error.
+ *
+ * @see ephysics_body_back_face_culling_set() for more details.
+ * @see ephysics_body_clockwise_get().
+ *
+ * @ingroup EPhysics_Body
+ */
+EAPI Eina_Bool ephysics_body_back_face_culling_get(const EPhysics_Body *body);
+
+/**
+ * @brief
+ * Get the clockwise state of a body.
+ *
+ * This determines if the points of the evas object associated to the @p body
+ * are clockwise or counter-clockwise. This can be used for "back-face culling". * This is where you hide objects that "face away" from you.
+ * In this case objects that are not clockwise.
+ *
+ * It can be set with @ref ephysics_body_back_face_culling_set(), so EPhysics
+ * will handle visibility automatically on evas object update.
+ *
+ * @note This information only will be updated on
+ * ephysics_body_evas_object_update(). So if a custom rendering is being done,
+ * this function won't return the current value of the evas object.
+ *
+ * @param body The physics body.
+ * @return @c EINA_TRUE if clockwise, @c EINA_FALSE otherwise or on error.
+ *
+ * @see ephysics_body_back_face_culling_set() for more details.
+ *
+ * @ingroup EPhysics_Body
+ */
+EAPI Eina_Bool ephysics_body_clockwise_get(const EPhysics_Body *body);
+
 /**
  * @}
  */

legacy/ephysics/src/lib/ephysics_body.cpp

@@ -1068,6 +1068,22 @@ _ephysics_body_evas_object_default_update(EPhysics_Body *body)
         evas_map_util_3d_perspective(map, px, py, z0, foc);
      }
 
+   if (body->back_face_culling)
+     {
+        if (evas_map_util_clockwise_get(map))
+          {
+             body->clockwise = EINA_TRUE;
+             evas_object_show(body->evas_obj);
+          }
+        else
+          {
+             body->clockwise = EINA_FALSE;
+             evas_map_free(map);
+             evas_object_hide(body->evas_obj);
+             return;
+          }
+     }
+
    if ((body->light_apply) ||
        (ephysics_world_light_all_bodies_get(body->world)))
      {
@@ -2173,8 +2189,6 @@ ephysics_body_evas_object_set(EPhysics_Body *body, Evas_Object *evas_obj, Eina_B
      }
 
    body->evas_obj = evas_obj;
-
-
    evas_object_event_callback_add(evas_obj, EVAS_CALLBACK_DEL,
                                   _ephysics_body_evas_obj_del_cb, body);
 
@@ -3160,6 +3174,39 @@ ephysics_body_volume_get(const EPhysics_Body *body)
    return _ephysics_body_volume_get(body);
 }
 
+EAPI void
+ephysics_body_back_face_culling_set(EPhysics_Body *body, Eina_Bool enable)
+{
+   if (!body)
+     {
+        ERR("Body is NULL.");
+        return;
+     }
+   body->back_face_culling = !!enable;
+}
+
+EAPI Eina_Bool
+ephysics_body_back_face_culling_get(const EPhysics_Body *body)
+{
+   if (!body)
+     {
+        ERR("Body is NULL.");
+        return EINA_FALSE;
+     }
+   return body->back_face_culling;
+}
+
+EAPI Eina_Bool
+ephysics_body_clockwise_get(const EPhysics_Body *body)
+{
+   if (!body)
+     {
+        ERR("Body is NULL.");
+        return EINA_FALSE;
+     }
+   return body->clockwise;
+}
+
 #ifdef  __cplusplus
 }
 #endif

legacy/ephysics/src/lib/ephysics_private.h

@@ -112,16 +112,19 @@ struct _EPhysics_Body {
      int cloth_columns;
      int cloth_rows;
      int anchor_prop;
-     Eina_Bool active:1;
-     Eina_Bool deleted:1;
-     Eina_Bool light_apply:1;
      int material_index;
-     Eina_Bool rebounding;
      struct {
        int triangle;
        double mass[3];
        Eina_Bool dragging;
      } dragging_data;
+
+     Eina_Bool active:1;
+     Eina_Bool deleted:1;
+     Eina_Bool light_apply:1;
+     Eina_Bool rebounding:1;
+     Eina_Bool back_face_culling:1;
+     Eina_Bool clockwise:1;
 };
 
 extern int _ephysics_log_dom;