定义称为“uniform” 的用法简介

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
glViewport(0, 0, width, height);
}

const char *vertexShaderSource = "#version 330 core "
"layout (location = 0) in vec3 aPos; "
"void main() "
"{ "
" gl_Position = vec4(aPos, 1.0); "
"}";
const char *fragmentShaderSource = "#version 330 core "
"out vec4 FragColor; "
"uniform vec4 ourColor; "
"void main() "
"{ "
" FragColor = ourColor; "
"} ";
int main()
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
//glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);

GLFWwindow* window = glfwCreateWindow(800, 600, "LearnOpenGL", NULL, NULL);

if (window == NULL)
{
std::cout << "Failed to create GLFW window" << std::endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}

glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
// build and compile our shader program
// ------------------------------------
// vertex shader
int vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
glCompileShader(vertexShader);
// check for shader compile errors
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 " << infoLog << std::endl;
}
// fragment shader
unsigned int fragmentShader[2];
fragmentShader[0] = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader[0], 1, &fragmentShaderSource, NULL);
glCompileShader(fragmentShader[0]);
// check for shader compile errors
glGetShaderiv(fragmentShader[0], GL_COMPILE_STATUS, &success);
if (!success)
{
glGetShaderInfoLog(fragmentShader[0], 512, NULL, infoLog);
std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED " << infoLog << std::endl;
}

//// fragment shader
//fragmentShader[1] = glCreateShader(GL_FRAGMENT_SHADER);
//glShaderSource(fragmentShader[1], 1, &fragmentShader2Source, NULL);
//glCompileShader(fragmentShader[1]);
//// check for shader compile errors
//glGetShaderiv(fragmentShader[1], GL_COMPILE_STATUS, &success);
//if (!success)
//{
// glGetShaderInfoLog(fragmentShader[1], 512, NULL, infoLog);
// std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED " << infoLog << std::endl;
//}

// link shaders
int shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader[0]);
//glAttachShader(shaderProgram, fragmentShader[1]);
glLinkProgram(shaderProgram);

/*int shaderProgram2 = glCreateProgram();
glAttachShader(shaderProgram2, vertexShader);
glAttachShader(shaderProgram2, fragmentShader[1]);
glLinkProgram(shaderProgram2);*/
// check for linking errors
glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
if (!success) {
glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED " << infoLog << std::endl;
}
glDeleteShader(vertexShader);
//glDeleteShader(fragmentShader[0]);
//glDeleteShader(fragmentShader[1]);
// set up vertex data (and buffer(s)) and configure vertex attributes
// ------------------------------------------------------------------
float vertices[] = {
-0.9f, -0.5f, 0.0f, // left
-0.0f, -0.5f, 0.0f, // right
-0.45f, 0.5f, 0.0f, // top
};

float vertices2[] = {
0.0f, -0.5f, 0.0f, // left
0.9f, -0.5f, 0.0f, // right
0.45f, 0.5f, 0.0f // top
};

unsigned int VBO[2], VAO[2];
glGenVertexArrays(2, VAO);
glGenBuffers(2, VBO);
// bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
glBindVertexArray(VAO[0]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE,0, (void*)0);
glEnableVertexAttribArray(0);

/*glBindVertexArray(VAO[1]);
glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);*/

while (!glfwWindowShouldClose(window))
{

/* glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);*/
// draw our first triangle
glUseProgram(shaderProgram);
glBindVertexArray(VAO[0]);
float timeValue = glfwGetTime();
float greenValue = (sin(timeValue) / 2.0f) + 0.5f;
int vertexColorLocation = glGetUniformLocation(shaderProgram, "ourColor");
glUniform4f(vertexColorLocation, 0.0f, greenValue, 0.0f, 1.0f);
glDrawArrays(GL_TRIANGLES, 0, 3);
/*glUseProgram(shaderProgram2);
glBindVertexArray(VAO[1]);
glDrawArrays(GL_TRIANGLES, 0, 3);*/
glfwSwapBuffers(window);
glfwPollEvents();
}

// optional: de-allocate all resources once they've outlived their purpose:
// ------------------------------------------------------------------------
glDeleteVertexArrays(2, VAO);
glDeleteBuffers(2, VBO);
glDeleteProgram(shaderProgram);

// glfw: terminate, clearing all previously allocated GLFW resources.
// ------------------------------------------------------------------
glfwTerminate();
return 0;
}