OpenGL教程:5. GLM数学库

GLM是OpenGL的数学库,提供了mat矩阵、vec向量等数据结构的运算,非常方便。

image-20230119165448513

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//
// Created by inver on 2022/9/12.
//
#include <iostream>
#include "glad/glad.h"
#include "GLFW/glfw3.h"
#include "Shader.h"

#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

int main() {
// GLM简单介绍
// 定义四维向量
glm::vec4 vec(1.0f, 0.0f, 0.0f, 1.0f);
// 定义变换矩阵,默认为单位矩阵:
// 1 0 0 0
// 0 1 0 0
// 0 0 1 0
// 0 0 0 1
glm::mat4 trans = glm::mat4(1.0f);
// 将单位矩阵弄成平移矩阵
// 1 0 0 x
// 0 1 0 y
// 0 0 1 z
// 0 0 0 1
// translate函数用来创建平移矩阵,第一个参数是作用矩阵,第二个参数是向量
trans = glm::translate(trans, glm::vec3(1.0f, 1.0f, 0.0f)); //后面的vec3的值对应x、y、z
vec = trans * vec;
std::cout << vec.x << ", " << vec.y << ", " << vec.z << std::endl;
// 此时向量变换为(2, 1, 0)


// rotate函数用来创建旋转矩阵,scale用于创建缩放矩阵
glm::mat4 mat2 = glm::mat4(1.0f);
mat2 = glm::rotate(mat2, glm::radians(90.0f),
glm::vec3(0.0f, 0.0f, 1.0f)); //第二个参数是旋转角度(radians转为弧度),第二个参数为旋转轴,这里绕z
mat2 = glm::scale(mat2, glm::vec3(0.5f, 0.5f, 0.5f)); //第二个参数是三个坐标的缩放倍数,这里缩小两倍
// 调用上面两个函数会使得mat2自动相乘,并且默认右乘,所以顺序反过来:先缩放、后旋转
vec = mat2 * vec;
std::cout << vec.x << ", " << vec.y << ", " << vec.z << std::endl;
// 此时向量变换为(-0.5, 1, 0)

// 初始化
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

GLFWwindow *window = glfwCreateWindow(800, 600, "GLM矩阵变换", nullptr, nullptr);
if (window == nullptr) {
std::cout << "Error: Fail to create window! \n";
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);

if (!gladLoadGLLoader((GLADloadproc) glfwGetProcAddress)) {
std::cout << "Error: Fail to initialize GLAD! \n";
return -1;
}

float vertices[] = {
-0.5f, -0.5f, 0.0f,
0.0f, 0.5f, 0.0f,
0.5f, -0.5f, 0.0f
};

unsigned int vbo;
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_DYNAMIC_DRAW);

unsigned int vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *) nullptr);
glEnableVertexAttribArray(0);

std::string vsh = "shaders\glm\glm.vsh";
std::string fsh = "shaders\glm\glm.fsh";
Shader shader(vsh, fsh);
shader.use();

while (!glfwWindowShouldClose(window)) {
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);

glm::mat4 mat = glm::mat4(1.0f);
// 角度随时间变化,所以是动态的旋转
mat = glm::rotate(mat, (float) glfwGetTime(), glm::vec3(0.0f, 0.0f, 1.0f));

// 获取uniform变量transform的地址
unsigned int transformLoc = glGetUniformLocation(shader.id, "transform");
// 将mat2矩阵传给transform(第一个参数是地址,第二个变量是矩阵的个数,第三个确认是否转置,第四个是矩阵的参数)
glUniformMatrix4fv(transformLoc, 1, GL_FALSE, glm::value_ptr(mat));

glDrawArrays(GL_TRIANGLES, 0, 3);

glfwSwapBuffers(window);
glfwPollEvents();
}
glDeleteProgram(shader.id);
glfwTerminate();

}

顶点着色器

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#version 330 core
layout (location = 0) in vec3 aPos;

uniform mat4 transform;

void main(){
gl_Position = transform * vec4(aPos, 1.0);
}

片元着色器

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#version 330 core
out vec4 FragColor;

void main(){
FragColor = vec4(0.5f, 0.5f, 0.2f, 1.0f);
}
Author

InverseDa

Posted on

2022-11-04

Updated on

2023-03-30

Licensed under

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