Rough Metal rasterization - swift

Question

I followed a tutorial to see how to draw a triangle in Metal. I am beginning metal, and what the issue is is that, the triangle has really rough edges. It's like the rasterizer is cutting corners. It looks pixelated, and the pixels of the triangle edges are much larger than my screen's pixels. How can I rasterize it smoother if I am using rasterization correctly?
import Cocoa
import MetalKit
class ViewController: NSViewController {
var MetalView: MTKView {
return view as! MTKView
}
var Device: MTLDevice!
var CommandQue: MTLCommandQueue!
var PipelineState: MTLRenderPipelineState?
var VertexBuffer: MTLBuffer?
override func viewDidLoad() {
super.viewDidLoad()
MetalView.device = MTLCreateSystemDefaultDevice()
Device = MetalView.device
MetalView.clearColor = MTLClearColorMake(0, 1, 1, 1)
CommandQue = Device.makeCommandQueue()
let CommandBuffer = CommandQue.makeCommandBuffer()
let CommandEncoder = CommandBuffer!.makeRenderCommandEncoder(descriptor: MetalView.currentRenderPassDescriptor!)
let Library = Device.makeDefaultLibrary()
let VertexFunction = Library!.makeFunction(name: "VertexShader")
let FragmentFunction = Library!.makeFunction(name: "FragmentShader")
let PipelineDescriptor = MTLRenderPipelineDescriptor()
PipelineDescriptor.vertexFunction = VertexFunction
PipelineDescriptor.fragmentFunction = FragmentFunction
PipelineDescriptor.colorAttachments[0].pixelFormat = .bgra8Unorm
do {
PipelineState = try Device.makeRenderPipelineState(descriptor: PipelineDescriptor)
} catch let Error as NSError {
print("Error: \(Error.localizedDescription)")
}
let Vertices: [Float] = [0, 1, 0, -1, -1, 0, 1, -1, 0]
VertexBuffer = Device.makeBuffer(bytes: Vertices, length: Vertices.count*MemoryLayout<Float>.size, options: [])
CommandEncoder!.setRenderPipelineState(PipelineState!)
CommandEncoder!.setVertexBuffer(VertexBuffer, offset: 0, index: 0)
CommandEncoder!.drawPrimitives(type: .triangle, vertexStart: 0, vertexCount: Vertices.count)
CommandEncoder!.endEncoding()
CommandBuffer!.present(MetalView.currentDrawable!)
CommandBuffer!.commit()
}
}

Answer 1

Not sure, but I think viewDidLoad is too early for rendering. The view might not have its final size here.
Instead, only perform the initialization code in viewDidLoad (pipeline state and buffers), register yourself as the delegate of the MTKView and then implement this callback function:
func draw(in view: MTKView) {
// your drawing code here
}
This is called every time you view gets drawn to the screen.

Answer 2

As Frank has suggested, viewDidLoad is not the place to issue draw calls. This way you are rendering only 1 frame.
About the aliasing, it depends on the resolution you are rendering in. But there are techniques to handle that, like smoothstep()ing edges in the fragment shader or post-processing anti-aliasing like rendering at higher resolution and then downsampling.
Also, in swift variables use camelCase, using PascalCase seems like you are calling statics on classes.