initial work to split into dart_filament and flutter_filament

flutter_filament/windows/include/filament/gltfio/Animator.h

@@ -0,0 +1,120 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef GLTFIO_ANIMATOR_H
+#define GLTFIO_ANIMATOR_H
+
+#include <gltfio/FilamentAsset.h>
+#include <gltfio/FilamentInstance.h>
+
+namespace filament::gltfio {
+
+struct FFilamentAsset;
+struct FFilamentInstance;
+struct AnimatorImpl;
+
+/**
+ * \class Animator Animator.h gltfio/Animator.h
+ * \brief Updates matrices according to glTF \c animation and \c skin definitions.
+ *
+ * Animator can be used for two things:
+ * - Updating matrices in filament::TransformManager components according to glTF \c animation definitions.
+ * - Updating bone matrices in filament::RenderableManager components according to glTF \c skin definitions.
+ *
+ * For a usage example, see the documentation for AssetLoader.
+ */
+class UTILS_PUBLIC Animator {
+public:
+    /**
+     * Applies rotation, translation, and scale to entities that have been targeted by the given
+     * animation definition. Uses filament::TransformManager.
+     *
+     * @param animationIndex Zero-based index for the \c animation of interest.
+     * @param time Elapsed time of interest in seconds.
+     */
+    void applyAnimation(size_t animationIndex, float time) const;
+
+    /**
+     * Computes root-to-node transforms for all bone nodes, then passes
+     * the results into filament::RenderableManager::setBones.
+     * Uses filament::TransformManager and filament::RenderableManager.
+     *
+     * NOTE: this operation is independent of \c animation.
+     */
+    void updateBoneMatrices();
+
+    /**
+     * Applies a blended transform to the union of nodes affected by two animations.
+     * Used for cross-fading from a previous skinning-based animation or rigid body animation.
+     *
+     * First, this stashes the current transform hierarchy into a transient memory buffer.
+     *
+     * Next, this applies previousAnimIndex / previousAnimTime to the actual asset by internally
+     * calling applyAnimation().
+     *
+     * Finally, the stashed local transforms are lerped (via the scale / translation / rotation
+     * components) with their live counterparts, and the results are pushed to the asset.
+     *
+     * To achieve a cross fade effect with skinned models, clients will typically call animator
+     * methods in this order: (1) applyAnimation (2) applyCrossFade (3) updateBoneMatrices. The
+     * animation that clients pass to applyAnimation is the "current" animation corresponding to
+     * alpha=1, while the "previous" animation passed to applyCrossFade corresponds to alpha=0.
+     */
+    void applyCrossFade(size_t previousAnimIndex, float previousAnimTime, float alpha);
+
+    /**
+     * Pass the identity matrix into all bone nodes, useful for returning to the T pose.
+     *
+     * NOTE: this operation is independent of \c animation.
+     */
+    void resetBoneMatrices();
+
+    /** Returns the number of \c animation definitions in the glTF asset. */
+    size_t getAnimationCount() const;
+
+    /** Returns the duration of the specified glTF \c animation in seconds. */
+    float getAnimationDuration(size_t animationIndex) const;
+
+    /**
+     * Returns a weak reference to the string name of the specified \c animation, or an
+     * empty string if none was specified.
+     */
+    const char* getAnimationName(size_t animationIndex) const;
+
+    // For internal use only.
+    void addInstance(FFilamentInstance* instance);
+
+private:
+
+    /*! \cond PRIVATE */
+    friend struct FFilamentAsset;
+    friend struct FFilamentInstance;
+    /*! \endcond */
+
+    // If "instance" is null, then this is the primary animator.
+    Animator(FFilamentAsset const* asset, FFilamentInstance* instance);
+    ~Animator();
+
+    Animator(const Animator& animator) = delete;
+    Animator(Animator&& animator) = delete;
+    Animator& operator=(const Animator&) = delete;
+
+    AnimatorImpl* mImpl;
+};
+
+} // namespace filament::gltfio
+
+#endif // GLTFIO_ANIMATOR_H