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  1. OpenGL Programming with Cocoa

OpenGL Programming -- Draw Rectangle

OpenGL Programming with Cocoa

创建 MyOpenGLView 类,继承自 NSOpenGLView 。头文件如下。

//
// MyOpenGLView.h
// opengl-mac
//
// Created by niyao on 5/17/18.
// Copyright © 2018 dourui. All rights reserved.
//
#import <Cocoa/Cocoa.h>
#import <OpenGL/gl3.h>
#import <OpenGL/OpenGL.h>
@interface MyOpenGLView : NSOpenGLView {
GLuint shaderProgram;
GLint positionUniform;
GLint colourAttribute;
GLint positionAttribute;
}
@end

实现文件如下。

//
// MyOpenGLView.m
// opengl-mac
//
// Created by niyao on 5/17/18.
// Copyright © 2018 dourui. All rights reserved.
//
#import "MyOpenGLView.h"
@implementation MyOpenGLView
- (instancetype)initWithFrame:(NSRect)frameRect {
if (self = [super initWithFrame:frameRect]) {
[self initGL];
}
return self;
}
- (void)initGL {
NSLog(@"...was here");
// 1. Create a context with opengl pixel format
NSOpenGLPixelFormatAttribute pixelFormatAttributes[] =
{
NSOpenGLPFAOpenGLProfile, NSOpenGLProfileVersion4_1Core,
NSOpenGLPFAColorSize , 24 ,
NSOpenGLPFAAlphaSize , 8 ,
NSOpenGLPFADoubleBuffer ,
NSOpenGLPFAAccelerated ,
NSOpenGLPFANoRecovery ,
0
};
NSOpenGLPixelFormat *pixelFormat = [[NSOpenGLPixelFormat alloc] initWithAttributes:pixelFormatAttributes];
super.pixelFormat = pixelFormat;
}
- (void)drawRect:(NSRect)dirtyRect {
[super drawRect:dirtyRect];
// 2. Make the context current
[[self openGLContext] makeCurrentContext];
// 3. Define and compile vertex and fragment shaders
GLuint vs;
GLuint fs;
const char *vss = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
" gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}\0";
const char *fss = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
" FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
"}\n\0";
vs = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vs, 1, &vss, NULL);
glCompileShader(vs);
fs = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fs, 1, &fss, NULL);
glCompileShader(fs);
printf("vs: %i, fs: %i\n",vs,fs);
int success;
char infoLog[512];
glGetShaderiv(vs, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(vs, 512, NULL, infoLog);
printf("ERROR::SHADER::VERTEX::COMPILATION_FAILED\n%s\n", infoLog);
}
glGetShaderiv(fs, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(fs, 512, NULL, infoLog);
printf("ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n%s\n", infoLog);
}
// 4. Attach the shaders
shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vs);
glAttachShader(shaderProgram, fs);
glLinkProgram(shaderProgram);
// check for linking errors
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
printf("ERROR::SHADER::PROGRAM::LINKING_FAILED\n%s\n", infoLog);
}
glDeleteShader(vs);
glDeleteShader(fs);
printf("positionUniform: %i, colourAttribute: %i, positionAttribute: %i\n",positionUniform,colourAttribute,positionAttribute);
// There is no space (or other values) between each set of 3 values. The values are tightly packed in the array.
float vertices[] = {
0.5f, 0.5f, 0.0f, // top right
0.5f, -0.5f, 0.0f, // bottom right
-0.5f, -0.5f, 0.0f, // bottom left
-0.5f, 0.5f, 0.0f // top left
};
unsigned int indices[] = { // note that we start from 0!
0, 1, 3, // first Triangle
1, 2, 3 // second Triangle
};
unsigned int VBO, VAO, EBO;
// bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
glGenVertexArrays(1, &VAO);
glBindVertexArray(VAO);
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glGenBuffers(1, &EBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
// note that this is allowed, the call to glVertexAttribPointer registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
glBindBuffer(GL_ARRAY_BUFFER, 0);
// remember: do NOT unbind the EBO while a VAO is active as the bound element buffer object IS stored in the VAO; keep the EBO bound.
//glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
// You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
// VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
glBindVertexArray(0);
// Drawing code here.
glViewport(10, 10, 100, 100);
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
// draw our first triangle
// glUseProgram(shaderProgram);
// glBindVertexArray(VAO);
// glDrawArrays(GL_TRIANGLES, 0, 3);
// glBindVertexArray(0);
glUseProgram(shaderProgram);
glBindVertexArray(VAO);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
[[self openGLContext] flushBuffer];
}
@end
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