GPU Programming: CocoaConf Atlanta
0 likes779 views
This document discusses GPU programming with GPUImage and Metal frameworks. It provides an overview of GPUs and how they are suited for parallel processing compared to CPUs. It also summarizes the history and evolution of OpenGL and OpenGL ES graphics APIs. Key frameworks for graphics programming on iOS like Core Animation, GLKit and SpriteKit are hardware accelerated. The document demonstrates GPUImage for image processing and introduces Metal as a new low-level graphics framework from Apple promising improved performance. While Metal requires deeper hardware understanding, it could be a potential game changer for parallel programming.
GPU Programming: CocoaConf Atlanta
- 1. GPU PROGRAMMING WITH GPUIMAGE AND METAL JANIE CLAYTON
- 2. About Me Janie Clayton Co-Author of “iOS 8 SDK Development” Software engineer at SonoPlot @redqueencoder http://redqueencoder.com
- 3. What is a GPU? A Graphics Processing Unit (GPU) is a small super computer that does one thing really really well. That one thing is processing floating point math in parallel. There are several applications for being able to do really fast floating point math: Graphics processing, bioinformatics, molecular dynamics, etc… Most people are going to primarily focus on graphics processing, as we will today. For GPGPU programming, go see Jeff Biggus speak about OpenCL!
- 4. What is Parallel Computing The default processes in a project is serialized computing. One instruction is processed at a time and then the CPU moves on to the next one. Parallel computing is the process of allowing multiple instructions to be carried out at once. Can be done on different threads, cores, and even at the bit level.
- 5. But I Have Concurrency! Concurrency is about dealing with a lot of things at once. Parallelism is about doing lots of things at once.
- 6. SERIES CIRCUIT LESS EFFICIENT
- 7. PARALLEL CIRCUIT MORE EFFICIENT
- 8. Shader Basics Shaders are the programs that determine what gets displayed on your screen. Shaders determine shapes, colors, textures, lighting… Everything you see and use comes down to shaders.
- 9. GRAPHICS ON IOS DEVICES
- 10. There are many levels of abstraction for graphics on iOS. Some frameworks are more abstracted than others.
- 11. UIKit Sprite Kit Core Animation/Graphics OpenGL ES/GLKit
- 12. A BRIEF HISTORY OF TIME, UH, OPENGL…
- 13. OpenGL Origins First released in 1992 Was an attempt to formalize a 3D graphic specification across platforms John Carmack was instrumental for the adoption of OpenGL as a cross-platform 3D graphic specification.
- 14. Problems with OpenGL Was created back when GPUs were not very powerful and existed on external graphics cards that could be swapped out The computer system architecture was vastly different when OpenGL was created. Things that were not very efficient then, like the GPU, are vastly more efficient now. Nothing is ever deprecated (Don’t ask Java programmers what that means, they don’t know)
- 16. Creation of OpenGL ES ES: Embedded Systems Wanted to strip out all of the dead code from OpenGL Was specifically tailored to work on less powerful devices like mobile phones
- 17. We don’t need a dozen turtles that all do the same thing
- 18. OpenGL ES Specifics Streamlined version of OpenGL Everything you can do in OpenGL ES can directly be ported to OpenGL Basically an optimized version of OpenGL
- 19. CPU VS GPU PROGRAMMING
- 20. CPU Expensive Tasks Sending hardware commands to the GPU (Changing State Vectors) Confirming that API usage is valid Compiling the shaders Interaction between the state and the shaders
- 21. How does the CPU Send tasks to the GPU? Try to envision a client-server process. Instead of your program sending an instruction over the network to a server and getting data back, you are sending instructions from your CPU to your GPU to be executed. Since you are sending instructions away from your client to be done elsewhere, you want to minimize this as much as possible.
- 22. How does the CPU Send tasks to the GPU? For example, in most Twitter client applications the client batches 20 or more Tweets in one call. This allows the application to feed tweets to the user without them having to wait for the network to deliver each and every tweet individually.
- 23. What Actually Sends Commands to the GPU? glGenBuffers(): Creates the buffer glBindBuffers(): Tells OpenGL to use this buffer. glBufferData(): Allocate this much continuous memory glVertexAttribPointer(): What kind of data do we have? glDrawArrays(): Render the data in the buffer glDeleteBuffer(): We don’t need the buffer anymore, get rid of it.
- 25. Fixed Function Pipeline Present in OpenGL ES 1.1 Shaders were hard-coded into OpenGL Easier to use, but were very limited
- 26. Programmable Pipeline Introduced in OpenGL ES 2.0 Shaders are now the responsibility of the programmer Harder to do, but provides far more flexibility and options for effects
- 27. What Frameworks are Hardware Accelerated? Core Animation GLKit SpriteKit SceneKit For more information on 2D drawing frameworks, go see “To drawRect, Or Not to drawRect” later today with Sam Davies.
- 28. What About Core Graphics/Quartz? Core Graphics/Quartz is NOT performed on the GPU. It is performed on the CPU. Core Graphics is off on its own. UIKit is written on top of Core Animation, which is written on top of the GPU. Core Graphics utilizes offscreen drawing. Anything using offscreen drawing is not hardware accelerated.
- 29. Offscreen Drawing Core Graphics (anything starting with “CG”) Every “drawRect()” method Anything using Core Text CALayers using masks and shadows CALayers with “shouldRasterize” set to YES Do not animate anything using offscreen drawing! It is horribly inefficient!!
- 31. GLSL OpenGL Shading Language (GLSL) Introduced in OpenGL 2.0 in 2004 C-like language for building shaders, which are small, efficient programs to run on the GPU Includes some specific data types and methods for processing geometry and graphics math that are not included in C
- 32. Vertex Shaders
- 33. Vertex Shaders The Vertex Shader would record the vertices of the star (which would be broken down into a series of triangles) The Vertex Shader would also specify that the area between the vertices is yellow. If there was a texture instead of a color, the shader would keep track of the texture coordinates.
- 34. Fragment Shaders
- 35. Fragment Shaders Fragment Shaders determine what pixels receive which color. Fragment shader performance has increased tremendously, so do as much work here as you can! If you look carefully at the star, there are areas outside the star that are yellow and areas inside that are white. If there is a gradient, the Fragment Shader will calculate what specific color each individual pixel will be.
- 36. GPU IMAGE
- 37. Creating GPUImage GPUImage dates back to iOS 5. Unlike Core Image (at the time), GPUImage utilized shaders more efficiently to make image processing faster. Core Image has been improved over the years and they are now comparable.
- 38. Why is GPUImage so Efficient? OpenGL ES tasks must be performed on one thread Many people utilize locks to manage the thread or, God forbid, only use the main thread. <shudder> NSLock is expensive to the CPU GPUImage utilizes a serial dispatch queue through GCD to manage anything that touches the GPU to keep everything happy and thread safe.
- 39. Demo
- 40. METAL: THE NEW KID IN TOWN
- 41. What does Metal Promise? Deep hardware integration between Apple chips and Apple frameworks General Purpose GPU programming (GPGPU) Precompiled Shaders up to 10 times more draw calls per frame Being able to perform draw calls on multiple threads
- 42. What Specifically are the CPU Expensive Tasks? Compiling Shaders Validating State Start Work on the GPU
- 43. Life Before Metal All three of these expensive tasks were done on each and every single draw call. All of these tasks don’t have to be done thousands of times a frame. Many can be done once, as long as the program knows that it does not have to continually check them.
- 44. Life After Metal Compiling Shaders: Now done when the applications builds Validating State: Now done when the content loads Start Work on the GPU: Still happens on each draw call. We can’t win them all…
- 45. Why is This Important? Before Metal, you would have to balance CPU time with GPU time. Tasks were so expensive that the GPU would usually not be used to capacity. Now that the CPU tasks are less expensive, you can take that time to generate more AI and do more programming logic.
- 46. Where Does Metal Help You? Metal helps you when you have a lot of objects that need to work independently of one another. Certain tasks, like image processing, do not involve a lot of objects, so you aren’t going to gain much with Metal.
- 47. ZEN GARDEN DEMO EPIC GAMES
- 48. SO, WHAT DO I THINK ABOUT METAL?
- 49. Why Metal is Scary You have to control EVERYTHING!!! You have to have a deep understanding of how the computer works that I have not seen demonstrated by a large number of people. Metal assumes you know more than the computer does, which in my experience is usually a bad move.
- 50. WHAT HAPPENS WHEN YOU LOOK INTO THE HEART OF THE GPU BAD WOLF PROJECT DATE 12/05/14 CLIENT
- 51. Why Metal is Exciting Metal, along with Swift, signals a shift to figuring out how to do more parallel programming. I believe Metal is not going anywhere. It will take a while for people to learn how to fully utilize it, but I believe it has the potential to be a game changer. Metal, like Swift, is still partly baked. It gives early adopters an opportunity to master something extraordinary.
- 52. IS THERE ANY POINT IN LEARNING OPENGL ES ANYMORE?
- 53. “Easy things should be easy. Hard things should be possible.” –Larry Wall
- 54. Yes, absolutely. Metal’s API is very similar to OpenGL ES. It will take a while for everyone to transition over to devices with A7 chips. Apple will continue to support its developers who work with OpenGL ES, especially since the Mac uses OpenGL and won’t be able to use Metal (yet). Also, Metal is new. It usually takes Apple a few years to work the kinks out of their new frameworks. Also, with Metal’s incredibly steep learning curve, very few people could work with it now.
- 55. Take Aways Whether you learn GLSL or Metal Shading Language, the value comes from the algorithms. The languages are not complicated and are similar. If you don’t know how the math on a shader works, knowing the language won’t really help you. There are lots of books on GPU programming out there explaining how to create effects, not to mention the shaders included in GPUImage. You will need to understand the math, but there are great resources online out there for this stuff. Be tenacious. This takes a lot of time to master. It is worth it. Be patient.
- 57. Think Different.
- 58. The End