shader-顶点颜色属性

1.顶点除了包含位置信息之外增加颜色属性

2.取顶点属性数据 步长 以及偏移量

3.上面的0 1 对应shader中的location

#include 
using namespace std;
#include 
#include 

void processInput(GLFWwindow *window);

float vertices[] = {
		 0.5f,  0.5f, 0.0f, 1.0f,0,0, // top right
		 0.5f, -0.5f, 0.0f,0,1,0, // bottom right
		-0.5f, -0.5f, 0.0f, 0,0,1, // bottom left
		-0.5f,  0.5f, 0.0f,1.0f,0.0f,1.0f   // top left 
};
unsigned int indices[] = {  // note that we start from 0!
	0, 1, 3,  // first Triangle
	1, 2, 3   // second Triangle
};

const char* vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"layout (location = 1) in vec3 aColor;\n"
"out vec4 vertexColor; \n"
"void main()\n"
"{\n"
"   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"   vertexColor = vec4(aColor.x,aColor.y,aColor.z,1.0);\n"
"}\0";

const char* fragShaderSource = "#version 330 core\n"
"in vec4 vertexColor;\n"
"out vec4 FragColor;\n"
"uniform vec4 ourColor;\n" 
"void main()\n"
"{\n"
"   FragColor = vertexColor;\n"
"}\0";

int main()
{
	glfwInit();  //初始化glfw库
	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, "OpenGL Window", NULL, NULL);

	if (window == NULL)
	{
		cout << "init window error" << endl;
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);


	//init glew
	//glewExperimental = GL_TRUE; //使用有问题 注释掉
	if (glewInit() != GLEW_OK)
	{
		cout << "glewInit error" << endl;
		glfwTerminate();
		return -1;
	}

	glViewport(0, 0, 800, 600);
	//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
	//创建VAO并且绑定
	unsigned int VAO;
	glGenVertexArrays(1, &VAO);
	glBindVertexArray(VAO);

	//创建VBO
	unsigned int VBO;
	glGenBuffers(1, &VBO);
	glBindBuffer(GL_ARRAY_BUFFER, VBO);

	//数据写入内存
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

	//创建EBO
	unsigned int EBO;
	glGenBuffers(1, &EBO);
	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);

	//数据写入内存
	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

	//创建顶点着色器 编译
	unsigned int vertexShader;
	vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);

	//创建片段着色器 编译
	unsigned int fragShader;
	fragShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragShader, 1, &fragShaderSource, NULL);
	glCompileShader(fragShader);

	//shader program 着色器和在一起 按顺序输入输出 链接 
	unsigned int shaderProgram;
	shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragShader);
	glLinkProgram(shaderProgram);

	//顶点位置属性
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(0);

	//顶点颜色属性
	glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*) (3 * sizeof(float)));
	glEnableVertexAttribArray(1);

	while (!glfwWindowShouldClose(window))
	{
		glfwPollEvents();

		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		glBindVertexArray(VAO);
		glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);

		float timeValue = glfwGetTime();
		float greenValue = (sin(timeValue) / 2.0f) + 0.5f;
		int vertexColorLocation = glGetUniformLocation(shaderProgram, "ourColor");
		glUseProgram(shaderProgram);
		glUniform4f(vertexColorLocation, 0.0f, greenValue, 0.0f, 1.0f);
		//glDrawArrays(GL_TRIANGLES, 0, 3);
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
		glfwSwapBuffers(window); //双缓存防止闪烁

		processInput(window);
	}
	return 0;
}

void processInput(GLFWwindow *window)
{
	if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
	{
		glfwSetWindowShouldClose(window, true);
	}
}