818afcb327
This changes the default shader loading strategy, implemented in the Metal driver, to compile the `MTLLibrary` on demand when the pipeline is created, which reduces cold startup time on IPHONE target OSs. Normally, the `MTLLibrary` is compiled from Metal source asynchronously when Godot calls `RenderingDeviceDriverMetal::shader_create_from_bytecode`; however, this changes this behaviour on mobile platforms to do it on demand when the pipeline is created, as noted in #96052, Godot will ask to create many more shaders from bytecode than are initially required. Mobile OSs like iOS are limited to compiling to shader libraries concurrently, which results in a significant bottleneck. This is not the default for macOS, as it can concurrently compile many shaders at once, resulting in faster startup times for the Godot editor.
Metal Rendering Device
This document aims to describe the Metal rendering device implementation in Godot.
Future work / ideas
- Use placement heaps
- Explicit hazard tracking
- MetalFX upscaling support?
Acknowledgments
The Metal rendering owes a lot to the work of the MoltenVK project, which is a Vulkan implementation on top of Metal. In accordance with the Apache 2.0 license, the following copyright notices have been included where applicable:
/**************************************************************************/
/* */
/* Portions of this code were derived from MoltenVK. */
/* */
/* Copyright (c) 2015-2023 The Brenwill Workshop Ltd. */
/* (http://www.brenwill.com) */
/* */
/* 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. */
/**************************************************************************/