Graphics processors are designed to quickly render graphics and perform data-parallel calculations. The Apple Metal framework allows you to communicate directly with the graphics processor available on a device. Applications that render complex scenes or that perform advanced scientific calculations can use this power to achieve maximum performance. Such applications include:
- Games that render sophisticated 3D environments;
- Video processing applications, like Final Cut Pro;
- Data-crunching applications, such as those used to perform scientific research.
Metal works hand-in-hand with other Apple frameworks that supplement its capability. MetalKit simplifies the task of getting your Metal content onscreen. Metal Performance Shaders implement custom rendering functions or to take advantage of a large library of existing functions.
Many high level Apple frameworks are built on top of Metal to take advantage of its performance, including Core Image, SpriteKit, and SceneKit. Using one of these high-level frameworks shields you from the details of graphics processor programming, but writing custom Metal code enables you to achieve the highest level of performance.
Metal and Lazarus
Metal support in Lazarus uses Ryan Joseph's lazmetalcontrol.
- You will need to have the latest version of Lazarus installed on a macOS computer (or better yet, have the latest Lazarus SVN version).
- You will need to download the Lazarus Metal Package (lazmetalcontrol) by Ryan Joseph.
- From Lazarus, choose the Package menu -> Open Package File and select lazmetalcontrol.lpk - install this into Lazarus.
- To use Metal you will need macOS 10.11 (El Capitan) or later and a Mac computer that supports Metal - typically Macs from 2012 and later.
The Lazarus 2.0.6 release for macOS contained a regression for OpenGL support. See Bugtracker Issue #35797 GLCocoaNSContext.pas now requires "cocoa_extra" in the Uses section.
Lazarus Example Code
ChrisR has created a few Lazarus projects that can be compiled for Apple's Metal Framework. The projects can be downloaded from GitHub and will compile on Lazarus provided you have met the requirements outlined above.
Most of the projects can also be compiled to support OpenGL 3.3 Core - providing support for Windows, Linux and older Macs. By keeping a thin layer for either OpenGL or Metal, one can retain most of the Lazarus write once, compile everywhere magic.
These example projects all use Lazarus. However, Ryan's repository also includes some examples of how to use Metal directly from Free Pascal without Lazarus.
See this Forum post with demo project for offscreen rendering in Metal.