Article directory
-
- Deprecated glBegin & amp; glEnd
- Examples of using the new API
Deprecated glBegin & amp; glEnd
Environment: glfw 3.3.8 + glad core
When OpenGL beginners try to use the glBegin and glEnd functions to draw triangles, they may find articles and code documents that use these functions.
But many of these functions have been deprecated in the core OpenGL specification
New API should be used to draw graphics
- Vertex Buffer Objects: Vertex Buffer Objects, VBOs
- Vertex Array Objects: Vertex Array Objects, VAOs
glBegin(GL_TRIANGLES); glColor3f(1.0f, 0.0f, 0.0f); //Set the color to red glVertex2f(-0.6f, -0.4f); // Vertex 1 glColor3f(0.0f, 1.0f, 0.0f); //Set the color to green glVertex2f(0.6f, -0.4f); // Vertex 2 glColor3f(0.0f, 0.0f, 1.0f); //Set the color to blue glVertex2f(0.0f, 0.6f); // Vertex 3 glEnd();
Examples of using the new API
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>
// window size
const int WINDOW_WIDTH = 800;
const int WINDOW_HEIGHT = 600;
//Vertex shader source code
const char* vertexShaderSource = R"(
#version 330 core
layout (location = 0) in vec3 aPos;
uniform float rotation;
mat3 getRotationMatrix(float angle) {
float s = sin(angle);
float c = cos(angle);
return mat3(
c, -s, 0.0,
s, c, 0.0,
0.0, 0.0, 1.0
);
}
void main()
{
mat3 rotationMatrix = getRotationMatrix(rotation);
gl_Position = vec4(rotationMatrix * aPos, 1.0);
}
)";
// Fragment shader source code
const char* fragmentShaderSource = R"(
#version 330 core
out vec4 FragColor;
uniform float time;
void main()
{
float red = sin(time);
float green = cos(time);
float blue = 0.5 + 0.5 * sin(2.0 * time);
FragColor = vec4(red, green, blue, 1.0);
}
)";
int main() {<!-- -->
//Initialize GLFW
if (!glfwInit()) {<!-- -->
std::cout << "GLFW initialization failed" << std::endl;
return -1;
}
// Configure GLFW
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
//Create window object
GLFWwindow* window = glfwCreateWindow(WINDOW_WIDTH, WINDOW_HEIGHT, "Triangle", nullptr, nullptr);
if (window == nullptr) {<!-- -->
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
//Set the window's context to the main context of the current thread
glfwMakeContextCurrent(window);
//Initialize GLAD
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {<!-- -->
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
//Create a vertex shader object
unsigned int vertexShader;
vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, & amp;vertexShaderSource, nullptr);
glCompileShader(vertexShader);
// Check whether the vertex shader was compiled successfully
int success;
char infoLog[512];
glGetShaderiv(vertexShader, GL_COMPILE_STATUS, & amp;success);
if (!success) {<!-- -->
glGetShaderInfoLog(vertexShader, 512, nullptr, infoLog);
std::cout << "Failed to compile vertex shader:\
" << infoLog << std::endl;
return -1;
}
// Create fragment shader object
unsigned int fragmentShader;
fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, & amp;fragmentShaderSource, nullptr);
glCompileShader(fragmentShader);
// Check whether the fragment shader compiled successfully
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, & amp;success);
if (!success) {<!-- -->
glGetShaderInfoLog(fragmentShader, 512, nullptr, infoLog);
std::cout << "Failed to compile fragment shader:\
" << infoLog << std::endl;
return -1;
}
// Create shader program object
unsigned int shaderProgram;
shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
// Check whether the shader program is linked successfully
glGetProgramiv(shaderProgram, GL_LINK_STATUS, & amp;success);
if (!success) {<!-- -->
glGetProgramInfoLog(shaderProgram, 512, nullptr, infoLog);
std::cout << "Failed to link shader program:\
" << infoLog << std::endl;
return -1;
}
//Delete shader object
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
//Set vertex data
float vertices[] = {<!-- -->
-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
0.0f, 0.5f, 0.0f,
0.0f, 0.0f, 0.0f //Origin coordinates
};
//Create a vertex buffer object (VBO) and a vertex array object (VAO)
unsigned int VBO, VAO;
glGenVertexArrays(1, & amp;VAO);
glGenBuffers(1, & amp;VBO);
// Bind VAO and VBO
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
//Set the vertex attribute pointer
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
// Unbind VAO and VBO
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
// Rendering loop
while (!glfwWindowShouldClose(window)) {<!-- -->
// Handle input events
glfwPollEvents();
// Clear the color buffer
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
//Use shader program
glUseProgram(shaderProgram);
// Get the current time
float time = glfwGetTime();
float rotation = time;
int rotationLocation = glGetUniformLocation(shaderProgram, "rotation");
glUniform1f(rotationLocation, rotation);
int timeLoadtion = glGetUniformLocation(shaderProgram, "time");
glUniform1f(timeLoadtion, time);
// Bind VAO
glBindVertexArray(VAO);
glDrawArrays(GL_POINTS, 3, 1); // Draw a point starting from index 3
// draw triangle
glDrawArrays(GL_TRIANGLES, 0, 3);
// Unbind VAO
glBindVertexArray(0);
// swap buffers
glfwSwapBuffers(window);
}
// Delete VAO and VBO
glDeleteVertexArrays(1, & amp;VAO);
glDeleteBuffers(1, & amp;VBO);
// Terminate GLFW
glfwTerminate();
return 0;
}