glEnableVertexAttribArray的作用解释： 默认情况下，出于性能考虑，所有顶点着色器的属性（Attribute）变量都是关闭的，意味着数据在着色器端是不可见的，哪怕数据已经上传到GPU，由glEnableVertexAttribArray启用指定属性，才可在顶点着色器中访问逐顶点的属性数据。 glVertexAttribPointer或VBO只是建立CPU和GPU之间的逻辑连接，从而实现了CPU数据上传至GPU。但是，数据在GPU端是否可见，即，着色器能否读取到数据，由是否启用了对应的属性决定，这就是glEnableVertexAttribArray的功能，允许顶点着色器读取GPU（服务器端）数据。 那么，glEnableVertexAttribArray应该在glVertexAttribPointer之前还是之后调用？答案是都可以，只要在绘图调用（glDraw*系列函数）前调用即可。
理论介绍：光照模型有很多种，这里介绍使用冯氏光照模型
冯氏光照模型
- 环境光照简单的处理复杂的光反射整体环境，用一个系数代替，比如0.1
- 漫反射，漫反射和 入射角、法线有关。注意：漫反射和观察视角无关。
- 镜面反射，与观察视角、反射角有关。注意：镜面反射有个反光度系数，反光度越高，反射越集中，会形成一个高光。 详细理论参考基础光照，或《计算机视觉基础-14章-视觉内容合成-p232》
实现效果：
光照效果
和教程上实现的有些区别，可能是位置没有调整好：
教程实现
代码：
- 代码目录：
代码没记录
- 顶点着色器和片元着色器实现（有两套着色器，灯光着色器实现不变，比较简单） colors.vs
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aNormal;
out vec3 FragPos;
out vec3 Normal;
uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;
void main()
{
FragPos = vec3(model * vec4(aPos, 1.0));
Normal = mat3(transpose(inverse(model))) * aNormal;
gl_Position = projection * view * vec4(FragPos, 1.0);
}colors.fs
代码语言：javascript复制#version 330 core
out vec4 FragColor;
in vec3 Normal;
in vec3 FragPos;
uniform vec3 lightPos;
uniform vec3 viewPos;
uniform vec3 objectColor;
uniform vec3 lightColor;
void main()
{
// 环境光照
float ambientStrength = 0.1;
vec3 ambient = ambientStrength * lightColor;
// 漫反射
vec3 norm = normalize(Normal);
vec3 lightDir = normalize(lightPos - FragPos);
float diff = max(dot(norm, lightDir), 0.0);
vec3 diffuse = diff * lightColor;
// 镜面反射
float specularStrength = 0.5;
vec3 viewDir = normalize(viewPos - FragPos);
vec3 reflectDir = reflect(-lightDir, norm);
float spec = pow(max(dot(viewDir, reflectDir), 0.0), 32);
vec3 specular = specularStrength * spec * lightColor;
vec3 result = (ambient diffuse) * objectColor;
FragColor = vec4(result, 1.0);
}- 主程序代码
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include "Shader.h"
#include "camera.h"
#include <iostream>
void framebuffer_size_callback(GLFWwindow* window, int width, int height);
void processInput(GLFWwindow *window);
void mouse_callback(GLFWwindow* window, double xpos, double ypos);
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset);
// settings
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;
// camera
Camera camera(glm::vec3(0.0f, 0.0f, 6.0f));
float lastX = SCR_WIDTH / 2.0f;
float lastY = SCR_HEIGHT / 2.0f;
bool firstMouse = true;
// timeing
float deltaTime = 0.0f;
float lastFrame = 0.0f;
glm::vec3 lightPos(1.2f, 1.0f, 2.0f);
int main()
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
#ifdef __APPLE__
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#endif
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;
}
glfwMakeContextCurrent(window);
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
glfwSetCursorPosCallback(window, mouse_callback);
glfwSetScrollCallback(window, scroll_callback);
// tell GLFW to capture our mouse
// 这一行，不注释也是ok的，隐藏鼠标
// glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
glEnable(GL_DEPTH_TEST);
Shader lightingShader("1.colors.vs", "1.colors.fs");
Shader lightCubeShader("1.light_cube.vs", "1.light_cube.fs");
float vertices[] = {
-0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f,
0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f,
0.5f, 0.5f, -0.5f, 0.0f, 0.0f, -1.0f,
0.5f, 0.5f, -0.5f, 0.0f, 0.0f, -1.0f,
-0.5f, 0.5f, -0.5f, 0.0f, 0.0f, -1.0f,
-0.5f, -0.5f, -0.5f, 0.0f, 0.0f, -1.0f,
-0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f,
0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f,
0.5f, 0.5f, 0.5f, 0.0f, 0.0f, 1.0f,
0.5f, 0.5f, 0.5f, 0.0f, 0.0f, 1.0f,
-0.5f, 0.5f, 0.5f, 0.0f, 0.0f, 1.0f,
-0.5f, -0.5f, 0.5f, 0.0f, 0.0f, 1.0f,
-0.5f, 0.5f, 0.5f, -1.0f, 0.0f, 0.0f,
-0.5f, 0.5f, -0.5f, -1.0f, 0.0f, 0.0f,
-0.5f, -0.5f, -0.5f, -1.0f, 0.0f, 0.0f,
-0.5f, -0.5f, -0.5f, -1.0f, 0.0f, 0.0f,
-0.5f, -0.5f, 0.5f, -1.0f, 0.0f, 0.0f,
-0.5f, 0.5f, 0.5f, -1.0f, 0.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.0f,
0.5f, 0.5f, -0.5f, 1.0f, 0.0f, 0.0f,
0.5f, -0.5f, -0.5f, 1.0f, 0.0f, 0.0f,
0.5f, -0.5f, -0.5f, 1.0f, 0.0f, 0.0f,
0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.0f,
0.5f, 0.5f, 0.5f, 1.0f, 0.0f, 0.0f,
-0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f,
0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f,
0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f,
0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f,
-0.5f, -0.5f, 0.5f, 0.0f, -1.0f, 0.0f,
-0.5f, -0.5f, -0.5f, 0.0f, -1.0f, 0.0f,
-0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f,
0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f,
0.5f, 0.5f, 0.5f, 0.0f, 1.0f, 0.0f,
0.5f, 0.5f, 0.5f, 0.0f, 1.0f, 0.0f,
-0.5f, 0.5f, 0.5f, 0.0f, 1.0f, 0.0f,
-0.5f, 0.5f, -0.5f, 0.0f, 1.0f, 0.0f
};
unsigned int VBO, cubeVAO;
glGenVertexArrays(1, &cubeVAO);
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glBindVertexArray(cubeVAO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)(3 * sizeof(float)));
glEnableVertexAttribArray(1);
unsigned int lightCubeVAO;
glGenVertexArrays(1, &lightCubeVAO);
glBindVertexArray(lightCubeVAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6*sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
while (!glfwWindowShouldClose(window)) {
float currentFrame = glfwGetTime();
deltaTime = currentFrame - lastFrame;
lastFrame = currentFrame;
//input
processInput(window);
//render
glClearColor(0.1f, 0.1f, 0.1f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
lightingShader.use();
lightingShader.setVec3("objectColor", 1.0f, 0.5f, 0.31f);
lightingShader.setVec3("lightColor", 1.0f, 1.0f, 1.0f);
lightingShader.setVec3("lightPos", lightPos);
lightingShader.setVec3("viewPos", camera.Position);
//view/projection transformations
glm::mat4 projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH/(float)SCR_HEIGHT, 0.1f, 100.0f);
glm::mat4 view = camera.GetViewMatrix();
lightingShader.setMat4("projection", projection);
lightingShader.setMat4("view", view);
glm::mat4 model = glm::mat4(1.0f);
model = glm::rotate(model, glm::radians(45.0f), glm::vec3(0.5, 1.0f, 0.0f));
lightingShader.setMat4("model", model);
//render the cube
glBindVertexArray(cubeVAO);
glDrawArrays(GL_TRIANGLES, 0, 36);
// also draw the lamp object
lightCubeShader.use();
lightCubeShader.setMat4("projection", projection);
lightCubeShader.setMat4("view", view);
model = glm::mat4(1.0f);
model = glm::translate(model, lightPos);
model = glm::scale(model, glm::vec3(0.2f));
lightCubeShader.setMat4("model", model);
glBindVertexArray(lightCubeVAO);
glDrawArrays(GL_TRIANGLES, 0, 36);
glfwSwapBuffers(window);
glfwPollEvents();
}
glDeleteVertexArrays(1, &cubeVAO);
glDeleteVertexArrays(1, &lightCubeVAO);
glDeleteBuffers(1, &VBO);
glfwTerminate();
return 0;
}
void processInput(GLFWwindow *window)
{
if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
{
glfwSetWindowShouldClose(window, true);
}
if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
{
camera.ProcessKeyboard(FORWARD, deltaTime);
}
if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
{
camera.ProcessKeyboard(BACKWARD, deltaTime);
}
if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS)
{
camera.ProcessKeyboard(LEFT, deltaTime);
}
if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS)
{
camera.ProcessKeyboard(RIGHT, deltaTime);
}
}
void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
glViewport(0, 0, width, height);
}
void mouse_callback(GLFWwindow* window, double xpos, double ypos)
{
if (firstMouse)
{
lastX = xpos;
lastY = ypos;
firstMouse = false;
}
float xoffset = xpos - lastX;
float yoffset = lastY - ypos;
lastX = xpos;
lastY = ypos;
camera.ProcessMouseMovement(xoffset, yoffset);
}
void scroll_callback(GLFWwindow* window, double xoffset, double yoffset)
{
camera.ProcessMouseScroll(yoffset);
}
