创建基础的光照场景（环境光和漫反射）

环境光照添加到场景里非常简单，用光的颜色乘以一个很小的常量环境因子，再乘以物体的颜色，然后将最终结果作为片段的颜色：

void main()
{
    float ambientStrength = 0.1;
    vec3 ambient = ambientStrength * lightColor;

    vec3 result = ambient * objectColor;
    FragColor = vec4(result, 1.0);
}

漫反射的计算稍微复杂些，计算漫反射时需要

1.法向量：一个垂直于顶点表面的向量

2.定向的光线：作为光源的位置与片段的位置之间向量差的方向向量。为了计算这个光线，我们需要光的位置向量和片段的位置向量。

漫反射的计算

 vec3 norm = normalize(Normal);
 vec3 lightDir = normalize(sunPos - FragPos);
 float diff = max(dot(norm, lightDir), 0.0);
 vec3 diffuse = diff * sunColor;

完整demo代码如下：

#include "stdio.h"
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <soil/SOIL.h>
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>

#include <iostream>
#include "wrapperWindow.h"
#include "wrapperShader.h"
#include "data.h"

const int design_w = 800;
const int design_h = 600;

int main()
{
	GLFWwindow *window = wrapperWindow(design_w, design_h).getWindow();

	auto m_shader = wrapperShader::createWithFilePath("triangle.vsh", "triangle.fsh");
	auto m_lightShader = wrapperShader::createWithFilePath("light.vsh", "light.fsh");
	int arr_group_nun = 6;

	GLuint vao, vbo;
	glGenVertexArrays(1, &vao);
	glBindVertexArray(vao);
	glGenBuffers(1, &vbo);
	glBindBuffer(GL_ARRAY_BUFFER,vbo);
	glBufferData(GL_ARRAY_BUFFER, sizeof(cubeNormalArr), cubeNormalArr, GL_STATIC_DRAW);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, arr_group_nun* sizeof(GLfloat), (GLvoid *)0);
	glEnableVertexAttribArray(0);

	glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, arr_group_nun* sizeof(GLfloat), (GLvoid *)(3 * sizeof(GLfloat)));
	glEnableVertexAttribArray(1);
	//--
	GLuint lightVao;
	glGenVertexArrays(1, &lightVao);
	glBindVertexArray(lightVao);
	glBindBuffer(GL_ARRAY_BUFFER, vbo);
	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, arr_group_nun* sizeof(GLfloat), (GLvoid *)0);
	glEnableVertexAttribArray(0);
	glBindBuffer(GL_ARRAY_BUFFER, 0);
	glBindVertexArray(0);
	//-----------
	//启用深度测试
	glEnable(GL_DEPTH_TEST);
	glm::vec3 lightPos(1.2f, 1.0f, 2.0f);
	while (!glfwWindowShouldClose(window))
	{
		glfwPollEvents();

		glClearColor(0.5f, 0.5f, 0.5f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
		
		m_shader.useShaderProgram();
		m_shader.setVec3("objectColor", 1.0f, 0.5f, 0.31f);
		m_shader.setVec3("sunColor", 1.0f, 1.0f, 1.0f);
		m_shader.setVec3("sunPos", lightPos);

		glm::mat4 view;
		view = glm::translate(view, glm::vec3(0.0f, 0.0f, -3.0f));
		m_shader.setMat4fv("view",view);

		glm::mat4 projection;
		projection = glm::perspective(glm::radians(45.0f), (float)(design_w*1.0 / design_h), 0.1f, 100.0f);
		m_shader.setMat4fv("projection", projection);

		glm::mat4 model;
		model = glm::rotate(model, (float)glfwGetTime()*glm::radians(25.0f), glm::vec3(1.0f, -1.0f, 0.0f));
		m_shader.setMat4fv("model", model);;

		glBindVertexArray(vao);
		//glBindTexture(GL_TEXTURE_2D,tex);
		glDrawArrays(GL_TRIANGLES, 0, 36);
		glBindVertexArray(0);

		//--
		m_lightShader.useShaderProgram();
		view = glm::translate(view, glm::vec3(0.0f, 0.0f, -3.0f));
		m_lightShader.setMat4fv("view", view);
		projection = glm::perspective(glm::radians(45.0f), (float)(design_w*1.0 / design_h), 0.1f, 100.0f);
		m_lightShader.setMat4fv("projection", projection);

		model = glm::mat4();
		model = glm::translate(model, lightPos);
		model = glm::scale(model, glm::vec3(0.2f));
		m_lightShader.setMat4fv("model", model);

		glBindVertexArray(lightVao);
		glDrawArrays(GL_TRIANGLES, 0, 36);
		glBindVertexArray(0);
		
		glfwSwapBuffers(window);
	}
	
	glfwTerminate();
	return 0;
}

效果图：