计算机图形学（3）：OpenGL对2D物体进行平移，旋转和缩放
配置OpenGL环境看第一篇文章
此代码为老师给的样例代码基础上进行修改
工程文件
效果图：
按WASD进行上下左右移动
按up和down进行缩放：
按left和right进行旋转：
首先全局定义要用到的一些变量：
float x_delta = 0.1f; //每次移动距离
float x_press_num = 0; //x偏移
float y_press_num = 0; //y偏移
glm::vec3 size = glm::vec3(1.0f); //物体大小
float angle = 0.0f; //旋转角度
创建和绑定好三角形的顶点和颜色信息：
在这里插入代码片
```cpp
const GLfloat triangle[] =
{
-0.5f, -0.5f, +0.0f, // left
+1.0f, +0.0f, +0.0f, // color
+0.5f, -0.5f, +0.0f, // right
+1.0f, +0.0f, +0.0f,
+0.0f, +0.5f, +0.0f, // top
+1.0f, +0.0f, +0.0f,
};
GLuint vaoID;
glGenVertexArrays(1, &vaoID);
glBindVertexArray(vaoID); //first VAO
GLuint vboID;
glGenBuffers(1, &vboID);
glBindBuffer(GL_ARRAY_BUFFER, vboID);
glBufferData(GL_ARRAY_BUFFER, sizeof(triangle), triangle, GL_STATIC_DRAW);
// vertex position
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), 0);
// vertex color
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (char*)(3 * sizeof(float)));
每次渲染初始化模型矩阵，对其进行响应的变化然后传到着色器中，最后画出三角形
glm::mat4 model = glm::mat4(1.0f);
model = glm::rotate(model, angle, glm::vec3(0.0f, 0.0f, 1.0f));
model = glm::translate(model, glm::vec3(x_delta * x_press_num, x_delta * y_press_num, 0.0f));
model = glm::scale(model, glm::vec3(size));
glUniformMatrix4fv(glGetUniformLocation(programID, "model"), 1, GL_FALSE, &model[0][0]);
glDrawArrays(GL_TRIANGLES, 0, 6); //render primitives from array data
定义按键事件：
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods) {
if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
if (key == GLFW_KEY_A && action == GLFW_PRESS) {
x_press_num -= 1;
}
if (key == GLFW_KEY_D && action == GLFW_PRESS) {
x_press_num += 1;
}
if (key == GLFW_KEY_W && action == GLFW_PRESS) {
y_press_num += 1;
}
if (key == GLFW_KEY_S && action == GLFW_PRESS) {
y_press_num -= 1;
}
if (key == GLFW_KEY_UP && action == GLFW_PRESS) {
size += glm::vec3(0.1f);
}
if (key == GLFW_KEY_DOWN && action == GLFW_PRESS) {
size -= glm::vec3(0.1f);
}
if (key == GLFW_KEY_LEFT && action == GLFW_PRESS) {
angle += 1.0f;
}
if (key == GLFW_KEY_RIGHT && action == GLFW_PRESS) {
angle -= 1.0f;
}
}
完整main.cpp
#include "Dependencies/glew/glew.h"
#include "Dependencies/GLFW/glfw3.h"
#include "Dependencies/glm/glm.hpp"
#include "Dependencies/glm/gtc/matrix_transform.hpp"
#include 顶点着色器：
#version 430
in layout(location=0) vec3 position;
in layout(location=1) vec3 vertexColor;
uniform mat4 model;
out vec3 theColor;
void main()
{
vec4 v = vec4(position, 1.0);
vec4 out_position = model * v;
gl_Position = out_position;
theColor = vertexColor;
}
片段着色器：
#version 430
out vec4 Color;
in vec3 theColor;
void main()
{
Color = vec4(theColor, 1.0);
}