/*

    Copyright (C) 2016 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    Basic mesh class that exposes buffers generated by Model I/O for rendering with Metal

*/

import Foundation

import Metal

import MetalKit

import ModelIO

class Mesh {

    var vertexBuffer: MTLBuffer

    var vertexDescriptor: MTLVertexDescriptor

    var primitiveType: MTLPrimitiveType

    var indexBuffer: MTLBuffer

    var indexCount: Int

    var indexType: MTLIndexType

    init?(cubeWithSize size: Float, device: MTLDevice)

    {

        let allocator = MTKMeshBufferAllocator(device: device)

        let mdlMesh = MDLMesh(boxWithExtent: vector_float3(size, size, size),

                              segments: vector_uint3(10, 10, 10),

                              inwardNormals: false,

                              geometryType: .triangles,

                              allocator: allocator)

        do {

            let mtkMesh = try MTKMesh(mesh: mdlMesh, device: device)

            let mtkVertexBuffer = mtkMesh.vertexBuffers[0]

            let submesh = mtkMesh.submeshes[0]

            let mtkIndexBuffer = submesh.indexBuffer

            vertexBuffer = mtkVertexBuffer.buffer

            vertexBuffer.label = "Mesh Vertices"

            vertexDescriptor = MTKMetalVertexDescriptorFromModelIO(mdlMesh.vertexDescriptor)

            primitiveType = submesh.primitiveType

            indexBuffer = mtkIndexBuffer.buffer

            indexBuffer.label = "Mesh Indices"

            indexCount = submesh.indexCount

            indexType = submesh.indexType

        } catch _ {

            return nil // Unable to create MTK mesh from MDL mesh

        }

    }

}