Help us understand the problem. What is going on with this article?

Objective-cでMetalを使用して三角形の色を変更しよう

More than 1 year has passed since last update.

Metalを使用して、シェーダーを使って、三角形の色を後から変更する覚書
「Objective-cでMetalを使用して三角形を描画しよう」を参照
https://qiita.com/sanoh/items/cfc7ecb057b7588c2a52

■Step1:シェーダー変更

まずはShaderType.h を追加します。
スクリーンショット 2018-11-26 19.56.03.png

ShaderType.h
#ifndef ShaderType_h
#define ShaderType_h

#ifdef __METAL_VERSION__
#define NS_ENUM(_type, _name) enum _name : _type _name; enum _name : _type
#define NSInteger metal::int32_t
#else
#import <Foundation/Foundation.h>
#endif

#include <simd/simd.h>

typedef NS_ENUM(NSInteger, BufferIndex)
{
    BufferIndexPositions = 0,
    BufferIndexUniforms  = 1
};

typedef struct
{
    float   color[3];
} Uniforms;

#endif /* ShaderType_h */

Shader.Metal を編集

Shader.metal
#include <metal_stdlib>
#import "ShaderType.h"

using namespace metal;

vertex float4 myVertexShader(const device packed_float3* vertex_array [[ buffer(BufferIndexPositions) ]],
                             unsigned int vid [[ vertex_id ]]) {
    return float4(vertex_array[vid], 1.0);
}

fragment half4 myFragmentShader(constant Uniforms & uniforms [[ buffer(BufferIndexUniforms) ]]) {
    return half4(uniforms.color[0],  uniforms.color[1], uniforms.color[2] , 1.0);
}

■Steop2:MetalRenderer.mを編集します。

MetalRenderer.m
#import "MetalRenderer.h"
#import "ShaderType.h"

static const NSUInteger MaxBuffersInFlight = 3;
static const size_t kAlignedUniformsSize = (sizeof(Uniforms) & ~0xFF) + 0x100;

@implementation MetalRenderer
{
    dispatch_semaphore_t _in_flight_semaphore;
    id <MTLDevice> _device;
    id <MTLCommandQueue> _command_queue;

    id <MTLRenderPipelineState> _pipeline_state;
    id <MTLBuffer>   _buffer_position;

    id <MTLBuffer> _dynamic_uniform_buffer; //<新規>
    uint8_t _uniform_buffer_index;          //<新規>
}

-(nonnull instancetype)initWithMetalKitView:(nonnull MTKView *)view;
{
    //頂点データ
    float vertices_array[]={
        0.0, 1.0, 0.0,
        -1.0, -1.0, 0.0,
        1.0, -1.0, 0.0,
    };
    if(self= [super init])
    {
        _device = view.device;
        _in_flight_semaphore = dispatch_semaphore_create(MaxBuffersInFlight);
        view.colorPixelFormat = MTLPixelFormatBGRA8Unorm;
        _command_queue = [_device newCommandQueue];
        //頂点情報の登録
        NSInteger size = sizeof(vertices_array);
        _buffer_position=[_device newBufferWithBytes:vertices_array
                                              length:size
                                             options:MTLResourceOptionCPUCacheModeDefault];
        //シェーダーの登録
        id <MTLLibrary> library = [_device newDefaultLibrary];
        MTLRenderPipelineDescriptor *descriptor = [[MTLRenderPipelineDescriptor alloc] init];
        descriptor.vertexFunction = [library newFunctionWithName:@"myVertexShader"];
        descriptor.fragmentFunction = [library newFunctionWithName:@"myFragmentShader"];
        descriptor.colorAttachments[0].pixelFormat=MTLPixelFormatBGRA8Unorm;
        NSError *error = NULL;
        _pipeline_state = [_device newRenderPipelineStateWithDescriptor:descriptor 
                                                                  error:&error];
        if (!_pipeline_state)
        {
            NSLog(@"Failed to created pipeline state, error %@", error);
        }
        //パラメータバッファの登録<新規>
        NSUInteger uniform_buffer_size = kAlignedUniformsSize * MaxBuffersInFlight;
        _dynamic_uniform_buffer = [_device newBufferWithLength:uniform_buffer_size
                                                       options:MTLResourceStorageModeShared];
    }
    return self;
}

- (void)drawInMTKView:(nonnull MTKView *)view
{
    dispatch_semaphore_wait(_in_flight_semaphore, DISPATCH_TIME_FOREVER);

    id <MTLCommandBuffer> command_buffer = [_command_queue commandBuffer];
    __block dispatch_semaphore_t block_sema = _in_flight_semaphore;
    [command_buffer addCompletedHandler:^(id<MTLCommandBuffer> buffer)
     {
         dispatch_semaphore_signal(block_sema);
     }];
    MTLRenderPassDescriptor* render_pass_descriptor = view.currentRenderPassDescriptor;
    render_pass_descriptor.colorAttachments[0].loadAction=MTLLoadActionClear;
    render_pass_descriptor.colorAttachments[0].storeAction=MTLStoreActionStore;
    render_pass_descriptor.colorAttachments[0].clearColor=MTLClearColorMake(1.0, 0.0, 0.0, 1.0);
    if(render_pass_descriptor != nil)
    {
        _uniform_buffer_index = (_uniform_buffer_index + 1) % MaxBuffersInFlight;
        //パラメータの更新<新規>
        uint32_t  uniform_buffer_offset = kAlignedUniformsSize * _uniform_buffer_index;
        void*     uniform_buffer_address = ((uint8_t*)_dynamic_uniform_buffer.contents) + uniform_buffer_offset;
        Uniforms * uniforms = (Uniforms*)uniform_buffer_address;
        uniforms->color[0]  = 0.0f;    //  R   色指定
        uniforms->color[1]  = 0.0f;    //  G
        uniforms->color[2]  = 1.0f;    //  B

        id <MTLRenderCommandEncoder> render_encoder = [command_buffer renderCommandEncoderWithDescriptor:render_pass_descriptor];
        //パラメータの設定<新規>
        [render_encoder setFragmentBuffer:_dynamic_uniform_buffer
                                   offset:uniform_buffer_offset
                                  atIndex:BufferIndexUniforms];
        //モデルの設定
        [render_encoder setRenderPipelineState:_pipeline_state];
        [render_encoder setVertexBuffer:_buffer_position 
                                 offset:0 
                                atIndex:BufferIndexPositions];
        [render_encoder drawPrimitives:MTLPrimitiveTypeTriangle 
                           vertexStart:0 
                           vertexCount:3];

        [render_encoder endEncoding];
        [command_buffer presentDrawable:view.currentDrawable];
    }
    [command_buffer commit];
}

- (void)mtkView:(nonnull MTKView *)view drawableSizeWillChange:(CGSize)size
{
}

@end

■Setp3:実行

iOsは実機で実行してくださいMacの場合は以下のようになります。
スクリーンショット 2018-11-26 19.56.26.png

Why do not you register as a user and use Qiita more conveniently?
  1. We will deliver articles that match you
    By following users and tags, you can catch up information on technical fields that you are interested in as a whole
  2. you can read useful information later efficiently
    By "stocking" the articles you like, you can search right away
Comments
Sign up for free and join this conversation.
If you already have a Qiita account
Why do not you register as a user and use Qiita more conveniently?
You need to log in to use this function. Qiita can be used more conveniently after logging in.
You seem to be reading articles frequently this month. Qiita can be used more conveniently after logging in.
  1. We will deliver articles that match you
    By following users and tags, you can catch up information on technical fields that you are interested in as a whole
  2. you can read useful information later efficiently
    By "stocking" the articles you like, you can search right away