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88 lines
3.7 KiB
88 lines
3.7 KiB
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This file is part of Magnum. |
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Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, |
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2020, 2021, 2022, 2023, 2024, 2025, 2026 |
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Vladimír Vondruš <mosra@centrum.cz> |
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Permission is hereby granted, free of charge, to any person obtaining a |
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copy of this software and associated documentation files (the "Software"), |
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to deal in the Software without restriction, including without limitation |
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the rights to use, copy, modify, merge, publish, distribute, sublicense, |
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and/or sell copies of the Software, and to permit persons to whom the |
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Software is furnished to do so, subject to the following conditions: |
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The above copyright notice and this permission notice shall be included |
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in all copies or substantial portions of the Software. |
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
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THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
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FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
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DEALINGS IN THE SOFTWARE. |
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.. |
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.. py:module:: magnum.scenegraph |
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The Python API for :dox:`SceneGraph` provides, similarly to C++, multiple |
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different transformation implementations. Recommended usage is importing |
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desired implementation akin to :cpp:`typedef`\ ing the types in C++: |
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.. code-figure:: |
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.. code:: c++ |
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#include <Magnum/SceneGraph/Object.h> |
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#include <Magnum/SceneGraph/Scene.h> |
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#include <Magnum/SceneGraph/MatrixTransformation3D.h> |
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typedef SceneGraph::Scene<SceneGraph::MatrixTransformation3D> Scene3D; |
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typedef SceneGraph::Object<SceneGraph::MatrixTransformation3D> Object3D; |
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C++ |
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.. code-figure:: |
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.. code:: py |
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from magnum import scenegraph |
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from magnum.scenegraph.matrix import Scene3D, Object3D |
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Python |
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`Scene vs Object`_ |
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================== |
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In C++, the Scene is a subclass of Object. However, because the Scene |
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object is not transformable nor it's possible to attach features to it, |
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most of the inherited API is unusable. This could be considered a wart of |
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the C++ API, so the Python bindings expose Scene and Object as two |
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unrelated types and all APIs that can take either a Scene or an Object |
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have corresponding overloads. |
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`Reference counting`_ |
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===================== |
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Compared to C++, the following is done with all Object instances created |
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on Python side: |
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- the object is additionally referenced by its parent (if there's any) |
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so objects created in local scope stay alive even after exiting the |
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scope |
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- deleting its parent (either due to it going out of scope or using |
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:py:`del` in Python) will cause it to have no parent instead of being |
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cascade deleted (unless it's not referenced anymore, in which case it's deleted as well) |
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- in order to actually destroy an object, it has to have no parent |
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For features it's slightly different: |
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- the feature is additionally referenced by the holder object so features |
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created in local scope stay alive even after exiting the scope |
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- deleting the holder object (either due to it going out of scope |
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or using :py:`del` in Python) will cause it to be without a holder |
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object (unless it's not referenced anymore, in which case it's deleted |
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as well) --- this makes any further operations on it impossible and |
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likely dangerous |
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- in order to actually destroy a feature, it has to have no holder object
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