1. 实现效果
2. 实现思路
(1)在片元处理器中添加uniform
变量
"uniform vec4 ourColor;\n"
(2)设置uniform
变量随时间变化
// 设置颜色随时间变化
double timeValue = glfwGetTime();
float greenValue = static_cast<float>(sin(timeValue) / 2.0 + 0.5);
int vertexColorLocation = glGetUniformLocation(shaderProgram, "ourColor");
glUniform4f(vertexColorLocation, 0.0f, greenValue, 0.0f,1.0f);
3. 具体代码
完整代码如下:
#include "glad\glad.h"
#include <GLFW/glfw3.h>
#include <iostream>
using namespace std;
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);
// 设置窗口宽和高
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;
// 顶点着色器
// "\0"是字符结尾
const char *vertexShaderSource =
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
" gl_Position = vec4(aPos, 1.0);\n"
"}\0";
// 片元着色器
const char *fragmentShaderSource =
"out vec4 FragColor;\n"
"uniform vec4 ourColor;\n"
"void main()\n"
"{\n"
" FragColor = ourColor;\n"
"}\n\0";
int main()
{
// glfw初始化及配置
glfwInit();
// 设置主次版本号及核心模式(只使用openGl的子集)
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
// 创建窗口
GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL);
if (window == NULL)
{
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
// 绑定上下文环境
glfwMakeContextCurrent(window);
// 当窗口大小变化时,调用回调函数
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
// 使用glad管理openGl指针
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
// 顶点着色器
unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
// 检查编译错误
int success;
char infoLog[512];
glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
}
// 片元着色器
unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader);
glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
}
// 链接着色器
unsigned int shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glLinkProgram(shaderProgram);
// 检查链接错误
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
}
glDeleteShader(vertexShader);
glDeleteShader(fragmentShader);
// 设置顶点数据并配置属性(三角形)
float vertices[] = {
0.5f, -0.5f, 0.0f,
-0.5f, -0.5f, 0.0f,
0.0f, 0.5f, 0.0f
};
unsigned int VBO, VAO;
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
// 绑定顶点数组对象
glBindVertexArray(VAO);
// 绑定顶点缓冲
glBindBuffer(GL_ARRAY_BUFFER, VBO);
// 设置顶点数据
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glBindVertexArray(VAO);
// 循环渲染(窗口不会被关闭)
while (!glfwWindowShouldClose(window))
{
// 处理输入
processInput(window);
// 使用自定义的颜色清空屏幕
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
// 清空颜色缓冲位
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(shaderProgram);
// 设置颜色随时间变化
double timeValue = glfwGetTime();
float greenValue = static_cast<float>(sin(timeValue) / 2.0 + 0.5);
int vertexColorLocation = glGetUniformLocation(shaderProgram, "ourColor");
glUniform4f(vertexColorLocation, 0.0f, greenValue, 0.0f,1.0f);
// 画三角形
glDrawArrays(GL_TRIANGLES, 0, 3);
// 交换颜色缓冲
glfwSwapBuffers(window);
// 检查是否有触发事件
glfwPollEvents();
}
glDeleteVertexArrays(1, &VAO);
glDeleteBuffers(1, &VBO);
glDeleteProgram(shaderProgram);
// glfwTerminate用于释放之前分配的GLFW资源
glfwTerminate();
return 0;
}
// 处理所有输入
void processInput(GLFWwindow *window)
{
if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
}
// 当窗口大小改变时的回调函数
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
// 控制视口,前两个参数为窗口左小角位置,后两个参数是窗口的宽度和高度
glViewport(0, 0, width, height);
}
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