英文:
Send a SIMD4<Float> to a Metal buffer
问题
我有一个被定义为SIMD4<Float>的颜色，并且想要将它发送到一个Metal缓冲区，如下所示：
var color = SIMD4<Float>(1, 0, 0, 0)
var colorBuffer: MTLBuffer!
let size = MemoryLayout<SIMD4<Float>>.size
colorBuffer = Renderer.device.makeBuffer(bytes: color, length: size)
但是这样做是行不通的，因为根据Xcode提供的错误信息，bytes必须是一个UnsafeRawPointer：
Cannot convert value of type 'SIMD4<Float>' to expected argument type 'UnsafeRawPointer'
那么我该如何获得color变量的UnsafeRawPointer呢？
英文:
I have a color defined as a SIMD4<Float> and would like to send it to a Metal buffer as shown below:
var color = SIMD4<Float>(1, 0, 0, 0)
var colorBuffer: MTLBuffer!
let size = MemoryLayout<SIMD4<Float>>.size
colorBuffer = Renderer.device.makeBuffer(bytes: color, length: size)
But this does not work because bytes must be an UnsafeRawPointer as seen from the error message provided by Xcode:
Cannot convert value of type 'SIMD4<Float>' to expected argument type 'UnsafeRawPointer'
So how do I get the UnsafeRawPointer for the color variable?
答案1
得分: 0
将颜色变量作为指针传递，使用&符号。例如：
colorBuffer = Renderer.device.makeBuffer(bytes: &color, length: size)
英文:
Pass in the color var with an & which provides a pointer. eg.
colorBuffer = Renderer.device.makeBuffer(bytes: &color, length: size)
答案2
得分: 0
您可以使用MTLBuffer的contents属性返回的UnsafeMutableRawPointer上的func storeBytes<T>(of: T, toByteOffset: Int, as: T.Type)方法来实现，示例如下：
var color = SIMD4<Float>(1, 0, 0, 0)
var colorBuffer: MTLBuffer!
let size = MemoryLayout<SIMD4<Float>>.size
colorBuffer = Renderer.device.makeBuffer(bytes: color, length: size)
colorBuffer.contents.storeBytes(of: color, toByteOffset: 0, as: SIMD4<Float>.self)
这段代码将color的值存储到了colorBuffer的内存中，偏移量为0。
英文:
You could use func storeBytes<T>(of: T, toByteOffset: Int, as: T.Type) on the UnsafeMutableRawPointer that is returned by contents property of the MTLBuffer like this:
var color = SIMD4<Float>(1, 0, 0, 0)
var colorBuffer: MTLBuffer!
let size = MemoryLayout<SIMD4<Float>>.size
colorBuffer = Renderer.device.makeBuffer(bytes: color, length: size)
colorBuffer.contents.storeBytes(of: color, toByteOffset: 0, as:SIMD4<Float>.self)
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