Implement sharing of bones for skinning

The API now allows to create a standalone SkinningBuffer containing
Bones for skinning. This SkinningBuffer can even be very large and
contain bone data for several renderables.

New APIs on RenderableManager allow to switch to skinning buffer mode
and to set the SkinningBuffer (and window into it) to use.


Fixes #3238

android/filament-android/src/main/cpp/SkinningBuffer.cpp

@@ -0,0 +1,116 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+#include <jni.h>
+
+#include <functional>
+#include <stdlib.h>
+#include <string.h>
+
+#include <filament/SkinningBuffer.h>
+
+#include "common/CallbackUtils.h"
+#include "common/NioUtils.h"
+
+using namespace filament;
+using namespace backend;
+
+extern "C"
+JNIEXPORT jlong JNICALL
+Java_com_google_android_filament_SkinningBuffer_nCreateBuilder(JNIEnv*, jclass) {
+    return (jlong) new SkinningBuffer::Builder();
+}
+
+extern "C"
+JNIEXPORT void JNICALL
+Java_com_google_android_filament_SkinningBuffer_nDestroyBuilder(JNIEnv*, jclass,
+        jlong nativeBuilder) {
+    SkinningBuffer::Builder* builder = (SkinningBuffer::Builder *) nativeBuilder;
+    delete builder;
+}
+
+extern "C"
+JNIEXPORT void JNICALL
+Java_com_google_android_filament_SkinningBuffer_nBuilderBoneCount(JNIEnv*, jclass,
+        jlong nativeBuilder, jint boneCount) {
+    SkinningBuffer::Builder* builder = (SkinningBuffer::Builder *) nativeBuilder;
+    builder->boneCount((uint32_t)boneCount);
+}
+
+extern "C"
+JNIEXPORT void JNICALL
+Java_com_google_android_filament_SkinningBuffer_nBuilderInitialize(JNIEnv*, jclass,
+        jlong nativeBuilder, jboolean initialize) {
+    SkinningBuffer::Builder* builder = (SkinningBuffer::Builder *) nativeBuilder;
+    builder->initialize((bool)initialize);
+}
+
+extern "C"
+JNIEXPORT jlong JNICALL
+Java_com_google_android_filament_SkinningBuffer_nBuilderBuild(JNIEnv*, jclass,
+        jlong nativeBuilder, jlong nativeEngine) {
+    SkinningBuffer::Builder* builder = (SkinningBuffer::Builder *) nativeBuilder;
+    Engine *engine = (Engine *) nativeEngine;
+    return (jlong) builder->build(*engine);
+}
+
+// ------------------------------------------------------------------------------------------------
+
+extern "C"
+JNIEXPORT jint JNICALL
+Java_com_google_android_filament_SkinningBuffer_nSetBonesAsMatrices(JNIEnv* env, jclass,
+        jlong nativeSkinningBuffer, jlong nativeEngine, jobject matrices, jint remaining, jint boneCount,
+        jint offset) {
+    SkinningBuffer *skinningBuffer = (SkinningBuffer *) nativeSkinningBuffer;
+    Engine *engine = (Engine *) nativeEngine;
+    AutoBuffer nioBuffer(env, matrices, boneCount * 16);
+    void* data = nioBuffer.getData();
+    size_t sizeInBytes = nioBuffer.getSize();
+    if (sizeInBytes > (remaining << nioBuffer.getShift())) {
+        // BufferOverflowException
+        return -1;
+    }
+    skinningBuffer->setBones(*engine,
+            static_cast<filament::math::mat4f const *>(data), (size_t)boneCount, (size_t)offset);
+    return 0;
+}
+
+extern "C"
+JNIEXPORT jint JNICALL
+Java_com_google_android_filament_SkinningBuffer_nSetBonesAsQuaternions(JNIEnv* env, jclass,
+        jlong nativeSkinningBuffer, jlong nativeEngine, jobject quaternions, jint remaining,
+        jint boneCount, jint offset) {
+    SkinningBuffer *skinningBuffer = (SkinningBuffer *) nativeSkinningBuffer;
+    Engine *engine = (Engine *) nativeEngine;
+    AutoBuffer nioBuffer(env, quaternions, boneCount * 8);
+    void* data = nioBuffer.getData();
+    size_t sizeInBytes = nioBuffer.getSize();
+    if (sizeInBytes > (remaining << nioBuffer.getShift())) {
+        // BufferOverflowException
+        return -1;
+    }
+    skinningBuffer->setBones(*engine,
+            static_cast<RenderableManager::Bone const *>(data), (size_t)boneCount, (size_t)offset);
+    return 0;
+}
+
+extern "C"
+JNIEXPORT jint JNICALL
+Java_com_google_android_filament_SkinningBuffer_nGetBoneCount(JNIEnv*, jclass,
+        jlong nativeSkinningBuffer) {
+    SkinningBuffer *skinningBuffer = (SkinningBuffer *) nativeSkinningBuffer;
+    return (jint)skinningBuffer->getBoneCount();
+}