CustomShaderWithMetalPetal

This repo shows how to process a stream of images with MetalPetal framework, using custom shaders (vertex and fragment).

Most of the files in this repo are self-explanatory. There are also additional comments within the individual files which should hopefully help.

Main features

1. Use of MTIGeometry protocol. (See DistortionGeometry Line: 19)

struct DistortionGeometry {
    
    let points: MTIGeometry
    
    init(width: Int, height: Int, cellSize: Int) {
        let size = SIMD2<Float>(Float(width), Float(height))
        let hMeshCount = (width + cellSize - 1) / cellSize
        let vMeshCount = (height + cellSize - 1) / cellSize
        
        // Create vertices
        var vertices = [MTIVertex]()
        for r in 0...vMeshCount {
            for c in 0...hMeshCount {
                let currentPosition = SIMD2<Float>(Float(c * cellSize), Float(r * cellSize))
                let targetPosition: SIMD2<Float> = (currentPosition)/size
                vertices.append(MTIVertex(position: SIMD4<Float>(x: (targetPosition.x - 0.5) * 2, y: ((1 - targetPosition.y) - 0.5) * 2, z: 0, w: 1),
                                          textureCoordinate: currentPosition/size))
            }
        }
        
        // Create indices
        var indices: [UInt32] = []
        for r in 1...vMeshCount {
            for c in 1...hMeshCount {
                let i = r * (hMeshCount + 1) + c
                let t = (r - 1) * (hMeshCount + 1) + c
                let tl = (r - 1) * (hMeshCount + 1) + c - 1
                let l = i - 1
                let t1: [UInt32] = [UInt32(i), UInt32(t), UInt32(tl)]
                let t2: [UInt32] = [UInt32(i), UInt32(l), UInt32(tl)]
                indices.append(contentsOf: t1)
                indices.append(contentsOf: t2)
            }
        }
        
        self.points = MTIVertices(vertexBuffer: MTIDataBuffer(mtiVertices: vertices)!,
                                vertexCount: UInt(vertices.count),
                                indexBuffer: MTIDataBuffer(uint32Indexes: indices)!,
                                indexCount: UInt(indices.count),
                                primitiveType: .triangle)
    }
}

2. Distortion Model declaration. (See DistortionParameters Line: 9)

struct DistortionParameters {
    var point: SIMD2<Float> = .zero
    var radius: Float = 0
    var direction: Float = 0
    var strength: Float = 0
    var density: Float = 0
    var width: Float = 0
    var height: Float = 0
}

3. Subclassing with MTIUnaryFilter. (See GADistortFilter Line: 63)

class GADistortFilter: NSObject, MTIUnaryFilter { ... }

4. Bonus:
   • Camera and CameraManager class
   • Console debugger
   • Controller mode observable

Word of caution ‼️

• This is not the prefered way of using the MetalPetal framework in your project.

  • I.e. use the suggested dependency package manager (CocoaPods or Swift Package Manager)

• We use it this way because some additions were made to some files for our own use.

Test it out ✅

1. Download this repo
2. Set Team signing
3. Connect physical device
4. Enjoy!

Sample image output📷

Issues ❓

If you experience any issues.

Create a new issue

• So everyone can benefit from it.