metal

I have a gradient, generated by a Metal fragment shader that I've applied to a SCNNode defined by a plane geometry. It looks like this: When I use the same shader applied to a MTKView rendered in an Xcode playground, the colors are darker. What is causing the colors to be lighter in the Scenekit version? Here is the Metal shader and the GameViewController. Shader: #include <metal_stdlib> using namespace metal; #include <SceneKit/scn_metal> struct myPlaneNodeBuffer { float4x4 modelTransform; float4x4 modelViewTransform; float4x4 normalTransform; float4x4 modelViewProjectionTransform; float2x3

What is the most efficient way to capture frames from a MTKView ? If possible, I would like to save a .mov file from the frames in realtime. Is it possible to render into an AVPlayer frame or something? It is currently drawing with this code (based on @warrenm PerformanceShaders project ): func draw(in view: MTKView) { _ = inflightSemaphore.wait(timeout: DispatchTime.distantFuture) updateBuffers() let commandBuffer = commandQueue.makeCommandBuffer() commandBuffer.addCompletedHandler{ [weak self] commandBuffer in if let strongSelf = self { strongSelf.inflightSemaphore.signal() } } // Dispatch

I'm allocating both input and output MTLBuffer using posix_memalign according to the shared GPU/CPU documentation provided by memkite. Aside: it is easier to just use latest API than muck around with posix_memalign let metalBuffer = self.metalDevice.newBufferWithLength(byteCount, options: .StorageModeShared) My kernel function operates on roughly 16 million complex value structs and writes out an equal number of complex value structs to memory. I've performed some experiments and my Metal kernel 'complex math section' executes in 0.003 seconds (Yes!), but writing the result to the buffer takes

I'm seeing very inconsistent frame rates in the SceneKit starter project. Sometimes it runs constantly at 60 fps (12ms rendering, 6ms metal flush), and sometimes it runs constantly at 40 fps (20ms rendering, 6ms metal flush), no more, no less. The frame rate changes randomly when I reopen the app, and will stay at that frame rate until the next reopen. I tried switching to OpenGL ES, and while it seems to fix it in the starter project, I still see those drops in my real app. The starter project is unmodified (rotating ship), and I'm testing it on Xcode 7.0 and iPad Mini 4 running iOS 9.0.1. I

Within our iOS app, we are using custom filters using Metal (CIKernel/CIColorKernel wrappers). Let's assume we have a 4K video and a custom video composition with a 1080p output size, that applies an advanced filter on the video buffers. Obviously, we don't need to filter the video in its original size, doing so we'll probably terminate the app with a memory warning (true story). This is the video-filtering pipeline: Getting the buffer in 4K (as CIImage ) --> Apply filter on the CIImage --> the filter applies the CIKernel Metal filter function on the CIImage --> Return the filtered CIImage to

Consider this admirable script which draws a (circular) gradient, https://github.com/paiv/AngleGradientLayer/blob/master/AngleGradient/AngleGradientLayer.m int w = CGRectGetWidth(rect); int h = CGRectGetHeight(rect); and then angleGradient(data, w, h .. and the it loops over all those for (int y = 0; y < h; y++) for (int x = 0; x < w; x++) { basically setting the color *p++ = color; But wait - wouldn't this be working by points, not pixels ? How, really, would you draw to the physical pixels on dense screens? Is it a matter of: Let's say the density is 4 on the device. Draw just as in the