split core renderer stuff into metal subfolder

Sources/Voxelotl/Renderer/Metal/PipelineOptions.swift

@@ -0,0 +1,23 @@
+import Metal
+
+internal struct PipelineOptions: Hashable {
+  let colorFormat: MTLPixelFormat, depthFormat: MTLPixelFormat
+  let shader: Shader
+  let blendFunc: BlendFunc
+}
+
+internal extension PipelineOptions {
+  func createPipeline(_ device: MTLDevice) throws -> MTLRenderPipelineState {
+    let pipeDescription = MTLRenderPipelineDescriptor()
+    pipeDescription.vertexFunction   = self.shader.vertexProgram
+    pipeDescription.fragmentFunction = self.shader.fragmentProgram
+    pipeDescription.colorAttachments[0].pixelFormat = self.colorFormat
+    self.blendFunc.setBlend(colorAttachment: &pipeDescription.colorAttachments[0])
+    pipeDescription.depthAttachmentPixelFormat = self.depthFormat
+    do {
+      return try device.makeRenderPipelineState(descriptor: pipeDescription)
+    } catch {
+      throw RendererError.initFailure("Failed to create pipeline state: \(error.localizedDescription)")
+    }
+  }
+}