1、总体代码
draw一个三角形,自写vertex着色器和fregment着色器,三角形染红色。
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>
static unsigned int CompileShader( unsigned int type, const std::string& source)
{
unsigned int id = glCreateShader(type);
const char* src = source.c_str();
glShaderSource(id, 1, &src,nullptr);
glCompileShader(id);
//TODO:Error handling
int result;
glGetShaderiv(id, GL_COMPILE_STATUS, &result);
if (result == GL_FALSE)
{
int length;
glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
char* message = (char*)alloca(length * sizeof(char));
glGetShaderInfoLog(id, length, &length, message);
std::cout << "Failed to compile " <<(type == GL_VERTEX_SHADER ? "vertex" : "fragment") << "shader!"
<< std::endl;
std::cout << message << std::endl;
glDeleteShader(id);
}
return id;
}
static unsigned int CreateShader(const std::string& vectexShader, const std::string& fragmentShader)
{
unsigned int program = glCreateProgram();
unsigned int vs = CompileShader(GL_VERTEX_SHADER, vectexShader);
unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);
glAttachShader(program, vs);
glAttachShader(program, fs);
glLinkProgram(program);
glValidateProgram(program);
glDeleteShader(vs);
glDeleteShader(fs);
return program;
}
int main(void)
{
GLFWwindow* window;
/* Initialize the library */
if (!glfwInit())
return -1;
/* Create a windowed mode window and its OpenGL context */
window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
if (!window)
{
glfwTerminate();
return -1;
}
/* Make the window's context current */
glfwMakeContextCurrent(window);
if (glewInit() != GLEW_OK)
std::cout << "GLEW INIT ERR" << std::endl;
std::cout << glGetString(GL_VERSION) << std::endl;
float position[6] = {
-0.5f, -0.5f,
0.0f, 0.5f,
0.5f, -0.5f,
};
unsigned int buffer;
glGenBuffers(1, &buffer);
glBindBuffer(GL_ARRAY_BUFFER, buffer);
glBufferData(GL_ARRAY_BUFFER, 6 * sizeof(float), position, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 2, 0);
std::string vertexShader =
"#version 330 core\n"
"\n"
"layout(location = 0) in vec4 position;\n"
"void main()\n"
"{\n"
" gl_Position = position;\n"
"}\n";
std::string fragmentShader =
"#version 330 core\n"
"\n"
"layout(location = 0) out vec4 color;\n"
"void main()\n"
"{\n"
" color = vec4(1.0, 0.0, 0.0, 1.0);\n" //RGB
"}\n";
unsigned int shader = CreateShader(vertexShader, fragmentShader);
glUseProgram(shader);
/* Loop until the user closes the window */
while (!glfwWindowShouldClose(window))
{
/* Render here */
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_TRIANGLES, 0, 3);
/* Swap front and back buffers */
glfwSwapBuffers(window);
/* Poll for and process events */
glfwPollEvents();
}
glDeleteProgram(shader);
glfwTerminate();
return 0;
}
2、解析
具体的gl函数文档可以见这个网站: opengl文档.
一个十分好用的中文网站:learnOpenGL-CN
-
glGenBuffers
glGenBuffers:生成缓冲区对象名称- 声明:void glGenBuffers( GLsizei n,
GLuint * buffers); - 参数:
- n :Specifies the number of buffer object names to be generated.指定要生成的缓冲区对象名称的数目。
- buffers :Specifies an array in which the generated buffer object names are stored. 指定存储生成的缓冲区对象名称的数组。
- 说明:
glGenBuffers returns n buffer object names in buffers. There is no guarantee that the names form a contiguous set of integers; however, it is guaranteed that none of the returned names was in use immediately before the call to glGenBuffers.
返回n个缓冲对象名称,不能保证名字会组成一个连续的整数集,但是能保证在调用unsigned int objectId = 0; glGenObject(1, &objectId);//我们首先创建一个对象,然后用一个id保存它的引用(实际数据被储存在后台)
glGenBuffers
前没有被立即使用过。
- 声明:void glGenBuffers( GLsizei n,
-
glBindBuffer
glBindBuffer