Got weird lighting result based on Phong model after learning LearnOpenGL chapter 13 - c++

Question

First incorrect result
Hello guys, I've been studying OpenGL on learnopengl.com and I found the result weird when I finished learning the basic lighting chapter. The result is I found specular light on the corner of the cube surface where the light could not reach. The strange result is shown in pictures below:
Even if the camera is hidden behind the cube from the light, the strange specular light still remains:
My vertex shader is:
#version 330 core
layout (location = 0) in vec3 aPos;
layout (location = 1) in vec3 aNormal;
layout (location = 2) in vec2 aTexCoords;
out vec3 FragPos;
out vec3 Normal;
uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;
uniform mat3 normalMatrix;
void main()
{
FragPos = vec3(model * vec4(aPos, 1.0));
Normal = normalMatrix * aNormal;
// Normal = aNormal;
gl_Position = projection * view * vec4(FragPos, 1.0);
}
My fragment shader is (the same as the official code provided by LearnOpenGL):
#version 330 core
out vec4 FragColor;
in vec3 Normal;
in vec3 FragPos;
uniform vec3 lightPos;
uniform vec3 viewPos;
uniform vec3 lightColor;
uniform vec3 objectColor;
void main()
{
// ambient
float ambientStrength = 0.1;
vec3 ambient = ambientStrength * lightColor;
// diffuse
vec3 norm = normalize(Normal);
vec3 lightDir = normalize(lightPos - FragPos);
float diff = max(dot(norm, lightDir), 0.0);
vec3 diffuse = diff * lightColor;
// specular
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 + specular) * objectColor;
FragColor = vec4(result, 1.0);
}
My source file is:
#include"glm/glm.hpp"
#include"glm/gtc/matrix_transform.hpp"
#include"glm/gtc/type_ptr.hpp"
#include<iostream>
#include"LearnOpenGL/camera.h"
#include "LearnOpenGL/stb_image.h"
#include "glad/glad.h"
#include <GLFW/glfw3.h>
#include"LearnOpenGL/shader_m.h"
#include <cmath>
#define STB_IMAGE_IMPLEMENTATION
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 attributes
Camera camera(glm::vec3(0.0f, 0.0f, 3.0f));
float lastX = SCR_WIDTH / 2.0f;
float lastY = SCR_HEIGHT / 2.0f;
bool firstMouse = true;
float fov = 45.0f;
// timing
float deltaTime = 0.0f; // time between current frame and last frame
float lastFrame = 0.0f; // time of last frame
// lighting
glm::vec3 lightPos(1.2f, 1.0f, 2.0f);
int main() {
// glfw: initialize and configure
// ------------------------------
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
// glfw window creation
// --------------------
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);
// glad: load all OpenGL function pointers
// ---------------------------------------
if (!gladLoadGLLoader((GLADloadproc) glfwGetProcAddress)) {
std::cout << "Failed to initialize GLAD" << std::endl;
return -1;
}
// cursor
glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
glfwSetCursorPosCallback(window, mouse_callback);
glfwSetScrollCallback(window, scroll_callback);
// shader declaration
Shader ourShader("../src/shaders/shader.vs", "../src/shaders/shader.fs");
Shader lightingShader("../src/shaders/lightsource_shader.vs", "../src/shaders/lightsource_shader.fs");
// set up vertex data (and buffer(s)) and configure vertex attributes
// ------------------------------------------------------------------
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
};
// first, configure the cube's VAO (and VBO)
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);
// position attribute
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void *) 0);
glEnableVertexAttribArray(0);
// normal attribute
glVertexAttribPointer(1,3,GL_FLOAT, GL_FALSE, 6*sizeof(float),(void*)0);
glEnableVertexAttribArray(1);
//second, configure the light's VAO (VBO stays the same; the vertices are the same for the light object which is also a 3D cube)
unsigned int lightCubeVAO;
glGenVertexArrays(1, &lightCubeVAO);
glBindVertexArray(lightCubeVAO);
// we only need to bind to the VBo (to link it with glVertexAtrribPointer), no need to fill it; the VBO's data already contains all we need (it's already bound, but we do it again for educational purposes)
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void *) 0);
glEnableVertexAttribArray(0);
glEnable(GL_DEPTH_TEST);
// render loop
// -----------
while (!glfwWindowShouldClose(window)) {
// per-frame time logic
// --------------------
float currentFrame = static_cast<float>(glfwGetTime());
deltaTime = glfwGetTime() - lastFrame;
lastFrame = glfwGetTime();
// input
// -----
processInput(window);
// render
// ------
// firstly clear the screen
glClearColor(0.1f, 0.1f, 0.1f, 0.1f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// activate shader
ourShader.use();
ourShader.setVec3("objectColor", 1.0f, 0.5f, 0.31f);
ourShader.setVec3("lightColor", 1.0f, 1.0f, 1.0f);
ourShader.setVec3("lightPos", lightPos);
ourShader.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();
ourShader.setMat4("projection", projection);
ourShader.setMat4("view", view);
// model transformation (aka world transformation)
glm::mat4 model = glm::mat4(1.0f);
ourShader.setMat4("model", model);
glm::mat3 normal_matrix = glm::transpose(glm::inverse(glm::mat3(model)));
// glm::mat3 normal_matrix = glm::mat3(glm::transpose(glm::inverse(model)));
ourShader.setMat3("normalMatrix", normal_matrix);
// render the cube
glBindVertexArray(cubeVAO);
glDrawArrays(GL_TRIANGLES, 0, 36);
// also draw the lamp object
lightingShader.use();
lightingShader.setMat4("projection", projection);
lightingShader.setMat4("view", view);
model = glm::mat4(1.0f);
model = glm::translate(model, lightPos);
model = glm::scale(model, glm::vec3(0.1f));
lightingShader.setMat4("model", model);
glBindVertexArray(cubeVAO);
glDrawArrays(GL_TRIANGLES, 0, 36);
// glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
// -------------------------------------------------------------------------------
glfwSwapBuffers(window);
glfwPollEvents();
}
// optional: de-allocate all resources once they've outlived their purpose:
// ------------------------------------------------------------------------
glDeleteVertexArrays(1, &cubeVAO);
glDeleteVertexArrays(1, &lightCubeVAO);
glDeleteBuffers(1, &VBO);
// glfw: terminate, clearing all previously allocated GLFW resources.
// ------------------------------------------------------------------
glfwTerminate();
return 0;
}
// process all input: query GLFW whether relevant keys are pressed/released this frame and react accordingly
// ---------------------------------------------------------------------------------------------------------
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);
}
// glfw: whenever the window size changed (by OS or user resize) this callback function executes
// ---------------------------------------------------------------------------------------------
void framebuffer_size_callback(GLFWwindow *window, int width, int height) {
// make sure the viewport matches the new window dimensions; note that width and
// height will be significantly larger than specified on retina displays.
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; // reversed: y ranges from bottom to top
lastX = xpos;
lastY = ypos;
camera.ProcessMouseMovement(xoffset, yoffset);
std::cout<<"cameraPos"<<camera.Position.x<<","<<camera.Position.y<<","<<camera.Position.z<<std::endl;
}
void scroll_callback(GLFWwindow *window, double xoffset, double yoffset) {
camera.ProcessMouseScroll(static_cast<float>(yoffset));
}
Other solutions I tried but didn't work
Furthermore, if I just use the specular result to generate the FragColor, the result would be like this:
in this case, my fragment shader is:
#version 330 core
out vec4 FragColor;
in vec3 Normal;
in vec3 FragPos;
uniform vec3 lightPos;
uniform vec3 viewPos;
uniform vec3 lightColor;
uniform vec3 objectColor;
void main()
{
// ambient
float ambientStrength = 0.1;
vec3 ambient = ambientStrength * lightColor;
// diffuse
vec3 norm = normalize(Normal);
vec3 lightDir = normalize(lightPos - FragPos);
float diff = max(dot(norm, lightDir), 0.0);
vec3 diffuse = diff * lightColor;
// specular
float specularStrength = 0.5;
vec3 viewDir = normalize(viewPos - FragPos);
float NdotL = dot(norm, lightDir);
vec3 specular = vec3(0.0);
if(NdotL > 0.0)
{
vec3 reflectDir = reflect(-lightDir, norm);
float spec = pow(max(dot(viewDir, reflectDir), 0.0), 32);
specular = specularStrength * spec * lightColor;
}
vec3 result = (ambient + diffuse + specular) * objectColor;
FragColor = vec4(result, 1.0);
}
The code above is inspired by the solution on OpenGL Phong lighting: specular highlight is wrong, but this solution turned out the above result.

Answer 1

You didn't set the offset for the normal vector attribute. The offset of the normal vector is 3*sizeof(float)
glVertexAttribPointer(1,3,GL_FLOAT, GL_FALSE, 6*sizeof(float),(void*)0);
glVertexAttribPointer(1,3,GL_FLOAT, GL_FALSE, 6*sizeof(float), (void*)(3*sizeof(float)));