Google Filament 渲染引擎(2)-Backend 核心类先容
Google Filament 渲染引擎(2)-Backend 核心类先容https://i-blog.csdnimg.cn/direct/f119900954cf42448731d881cb1f1ab0.png
阅读分析:
[*]本文基于 filament 版本: v1.58.0
[*]文本更加论述 Backend 内部核心类的关系, 示例代码作了非常多的删减和简化
文本将以创建纹理为例, 论述 Backend 内部的流程。后端图形接口以 OpenGL 为例。
核心类的功能概览:
[*]Dispatcher: 本质上只是一个函数指针的集合，用于将命令与驱动接口的方法绑定。在初始化阶段，这些函数指针就被填充好。
[*]Driver: 负责管理底层驱动的状态，以及与硬件交互的详细实现。
[*]CommandStream: 负责接收命令，并将其发送到驱动。
[*]Command: 命令对象，包含了详细的命令类型和参数, 负责命令的封装和执行.
[*]Engine: 负责管理资源的创建和烧毁，以及命令的提交。
一、底层驱动初始化
// --------------------------------- step1: 创建 Driver ----------------------------------
Backend mBackend = Backend::OPENGL;
// 根据类型选择平台, 以 PlatformCocoaGL 为例
PlatformCocoaGL platform = filament::backend::PlatformFactory::create(&mBackend);
// 根据平台创建驱动, 这里 driver 的类型是 OpenGLDriver
Driver* driver = platform->createDriver();
// --------------------------------- step2: 创建 CommandStream ----------------------------------
using DriverApi = filament::backend::CommandStream;
// 这里完成 底层驱动 绑定到 CommandStream 的 Dispatcher 上
DriverApi* driverApi = new DriverApi(*driver);
二、创建纹理
应用层创建代码:
filament::Texture* texture = Texture::Builder()
.levels(1)
.sampler(Texture::Sampler::SAMPLER_EXTERNAL)
.build(*mEngine);
Texture* Texture::Builder::build(Engine& engine) {
// 调用 Engine 的 createTexture 方法
return downcast(engine).createTexture(*this);
}
三、核心类
1、Engine
// ====> 模板展开后的 createTexture 函数
FTexture* FEngine::createTexture(const Texture::Builder& builder) noexcept {
// 展开 create 模板调用
FTexture* p = mHeapAllocator.make<FTexture>(*this, builder);
if (p) {
mTextures.insert(p);
}
return p;
}
FTexture::FTexture() {
backend::Handle<backend::HwTexture> mHandle;
// driver 的实际类型是 CommandStream
FEngine::DriverApi& driver = engine.getDriverApi();
mHandle = driver.createTexture(
mTarget, mLevelCount, mFormat, mSampleCount, mWidth, mHeight, mDepth, mUsage);
}
2、CommandStream
// 构造函数:
CommandStream::CommandStream(Driver& driver, CircularBuffer& buffer) noexcept
: mDriver(driver),
mCurrentBuffer(buffer),
mDispatcher(driver.getDispatcher())
{
}
// 纹理创建函数
inline backend::TextureHandle createTexture(
backend::SamplerType target,
uint8_t levels,
backend::TextureFormat format,
uint8_t samples,
uint32_t width,
uint32_t height,
uint32_t depth,
backend::TextureUsage usage) {
// 分配结构体内存
backend::TextureHandle result = this->mDriver.createTextureS();
// 定义命令类型
using Cmd = CommandType<decltype(&Driver::createTextureR)>::Command<&Driver::createTextureR>;
// 分配命令缓冲区内存
void* const p = this->allocateCommand(CommandBase::align(sizeof(Cmd)));
// 在分配的内存上构造命令对象
new (p) Cmd(
// 真正需要执行的命令
this->mDispatcher.createTexture_,
backend::TextureHandle(result),
std::move(target),
std::move(levels),
std::move(format),
std::move(samples),
std::move(width),
std::move(height),
std::move(depth),
std::move(usage)
);
return result;
}
3、Command
// 特化模板类 Command
template<>
class Command<&filament::backend::Driver::createTextureR> : public filament::backend::CommandBase {
using SavedParameters = std::tuple<
std::remove_reference_t<filament::backend::Handle<filament::backend::HwTexture>>,
std::remove_reference_t<filament::backend::SamplerType>,
std::remove_reference_t<unsigned char>,
std::remove_reference_t<filament::backend::TextureFormat>,
std::remove_reference_t<unsigned char>,
std::remove_reference_t<unsigned int>,
std::remove_reference_t<unsigned int>,
std::remove_reference_t<unsigned int>,
std::remove_reference_t<filament::backend::TextureUsage>
>;
SavedParameters mArgs;
void log() noexcept;
template <std::size_t ...I>
void log(std::index_sequence<I...>) noexcept;
public:
template <typename M, typename D>
static inline void execute(M &&method, D &&driver, filament::backend::CommandBase *base, intptr_t *next);
inline Command(Command<&filament::backend::Driver::createTextureR> &&rhs) noexcept = default;
template <typename ...A>
inline constexpr explicit Command(filament::backend::Execute execute, A &&...args);
template<>
inline constexpr explicit Command<filament::backend::Handle<filament::backend::HwTexture>,
filament::backend::SamplerType,
unsigned char,
filament::backend::TextureFormat,
unsigned char,
unsigned int,
unsigned int,
unsigned int,
filament::backend::TextureUsage>(
filament::backend::Execute execute,
filament::backend::Handle<filament::backend::HwTexture> &&arg1,
filament::backend::SamplerType &&arg2,
unsigned char &&arg3,
filament::backend::TextureFormat &&arg4,
unsigned char &&arg5,
unsigned int &&arg6,
unsigned int &&arg7,
unsigned int &&arg8,
filament::backend::TextureUsage &&arg9
) : filament::backend::CommandBase(execute),
mArgs(std::forward<filament::backend::Handle<filament::backend::HwTexture>>(arg1),
std::forward<filament::backend::SamplerType>(arg2),
std::forward<unsigned char>(arg3),
std::forward<filament::backend::TextureFormat>(arg4),
std::forward<unsigned char>(arg5),
std::forward<unsigned int>(arg6),
std::forward<unsigned int>(arg7),
std::forward<unsigned int>(arg8),
std::forward<filament::backend::TextureUsage>(arg9)) {
}
static inline void *operator new(std::size_t, void *ptr) {
if (__builtin_expect(!(ptr), false)) {
utils::panic(__func__, "root/filament/filament/backend/include/private/backend/CommandStream.h", 159, "ptr");
}
return ptr;
}
};
4、Driver
1)命令的绑定
Dispatcher OpenGLDriver::getDispatcher() const noexcept {
auto dispatcher = ConcreteDispatcher<OpenGLDriver>::make();
return dispatcher;
}
2)分配结构体内存
struct GLTexture : public HwTexture {
using HwTexture::HwTexture;
struct GL {
GL() noexcept : imported(false), external(false), sidecarSamples(1), reserved1(0) {}
GLuint id = 0; // texture or renderbuffer id
GLenum target = 0;
GLenum internalFormat = 0;
GLuint sidecarRenderBufferMS = 0;// multi-sample sidecar renderbuffer
// texture parameters go here too
GLfloat anisotropy = 1.0;
int8_t baseLevel = 127;
int8_t maxLevel = -1;
uint8_t reserved0 = 0;
bool imported : 1;
bool external : 1;
uint8_t sidecarSamples: 3;
uint8_t reserved1 : 3;
std::array<TextureSwizzle, 4> swizzle{
TextureSwizzle::CHANNEL_0,
TextureSwizzle::CHANNEL_1,
TextureSwizzle::CHANNEL_2,
TextureSwizzle::CHANNEL_3
};
} gl;
mutable Handle<GLTextureRef> ref;
OpenGLPlatform::ExternalTexture* externalTexture = nullptr;
};
// 分配内存并构造一个 filament::backend::GLTexture 对象
template<> Handle<GLTexture> initHandle<filament::backend::GLTexture, <>>() {
return this->mHandleAllocator.allocateAndConstruct<filament::backend::GLTexture>();
}
Handle<HwTexture> OpenGLDriver::createTextureS() noexcept {
return this->initHandle<GLTexture>();
}
3)使用 OpenGL API 创建纹理
void OpenGLDriver::createTextureR(Handle<HwTexture> th, SamplerType target, uint8_t levels,
TextureFormat format, uint8_t samples, uint32_t w, uint32_t h, uint32_t depth,
TextureUsage usage) {
auto &gl = this->mContext;
glTexStorage2D(t->gl.target, GLsizei(t->levels), t->gl.internalFormat, GLsizei(width), GLsizei(height));
// ...
}
5、Dispatcher
using Execute = void (*)(Driver& driver, CommandBase* self, intptr_t* next);
Execute createTexture_;
// 这里完成 底层驱动 绑定到 Dispatcher 上
template <typename ConcreteDriver> class ConcreteDispatcher {
static void createTexture(Driver &driver, CommandBase *base, intptr_t *next) {
using Cmd = CommandType<decltype(&Driver::createTextureR)>::Command<&Driver::createTextureR>;
ConcreteDriver &concreteDriver = static_cast<ConcreteDriver &>(driver);
Cmd::execute(& ConcreteDriver::createTextureR, concreteDriver, base, next);
}
}
template <typename ConcreteDriver> Dispatcher ConcreteDispatcher<ConcreteDriver>::make() {
Dispatcher dispatcher;
dispatcher.createTexture_ = &ConcreteDispatcher<T>::createTexture;
// ...
return dispatcher;
}
四、总结
这表明 Engine -> CommandStream -> Dispatcher 形成了调用链，每一层都负责不同的任务，Engine 负责 API 层接口，CommandStream 负责命令封装，Dispatcher 负责命令派发, Driver 负责最终执行。
五、辅助工具
1)Engine
命令出处：
cmake-build-debug/compile_commands.json
预处置惩罚命令:
// root/filament:
clang++ -E \
-I../libs/filabridge/include \
-I../third_party/robin-map \
-I../libs/utils/include \
-I../libs/filaflat/include \
-I../libs/math/include \
-I../cmake-build-debug/filament/ \
-I./include \
-I./backend/include \
-I./src/details \
-I./components \
-I./src \
./src/details/Engine.cpp -o 123.cpp
编译模板睁开:
// root/filament:
clang++ \
-Xclang -ast-print -fsyntax-only -std=c++17 \
root/filament/filament/src/Engine.cpp > record_layouts.txt 2>&1 \
-Iroot/filament/filament/include \
-Iroot/filament/cmake-build-debug/filament \
-Iroot/filament/filament/src \
-Iroot/filament/filament/backend/include \
-Iroot/filament/libs/math/include \
-Iroot/filament/libs/utils/include \
-Iroot/filament/third_party/robin-map/tnt/.. \
-Iroot/filament/libs/bluevk/include \
-Iroot/filament/third_party/vkmemalloc/tnt/../include \
-Iroot/filament/third_party/smol-v/tnt/../source \
-Iroot/filament/libs/filaflat/include \
-Iroot/filament/libs/filabridge/include \
-Iroot/filament/libs/ibl/include \
-Iroot/filament/libs/matdbg/include \
-Iroot/filament/third_party/civetweb/tnt/../include \
-Iroot/filament/libs/filamat/include \
-Iroot/filament/cmake-build-debug/shaders \
-Iroot/filament/cmake-build-debug/include \
-Iroot/filament/third_party/glslang/glslang/tnt/../Include \
-Iroot/filament/third_party/glslang/glslang/tnt/../Public \
-Iroot/filament/third_party/glslang/glslang/tnt/../MachineIndependent \
-Iroot/filament/third_party/glslang/glslang/tnt/../.. \
-Iroot/filament/third_party/glslang/SPIRV/tnt/.. \
-Iroot/filament/third_party/glslang/SPIRV/tnt/../.. \
-Iroot/filament/third_party/spirv-tools/include \
-Iroot/filament/third_party/spirv-headers/include \
-Iroot/filament/third_party/spirv-cross/tnt/..
2)CommandStream
预处置惩罚命令:
// root/filament/backend:
g++ -E -I../../libs/utils/include -I../../libs/math/include -I../include -I./include./src/CommandStream.cpp -o CommandStream.i
3)Driver
clang++ \
-Xclang -ast-print -fsyntax-only -std=c++17 \
root/filament/backend/src/opengl/OpenGLDriver.cpp > record_layouts.txt 2>&1 \
-Iroot/filament/include \
-Iroot/cmake-build-debug/filament \
-Iroot/filament/src \
-Iroot/filament/backend/include \
-Iroot/filament/backend/src \
-Iroot/cmake-build-debug/filament/backend \
-Iroot/libs/math/include \
-Iroot/libs/utils/include \
-Iroot/third_party/robin-map/tnt/.. \
-Iroot/libs/bluegl/include \
-Iroot/libs/bluevk/include \
-Iroot/third_party/vkmemalloc/tnt/../include \
-Iroot/third_party/smol-v/tnt/../source \
-Iroot/third_party/spirv-headers/include
免责声明：如果侵犯了您的权益，请联系站长，我们会及时删除侵权内容，谢谢合作！更多信息从访问主页：qidao123.com:ToB企服之家，中国第一个企服评测及商务社交产业平台。
页:
[1]