OpenGL 3.x Assimp trouble implementing phong shading (normals?) - c++

Question

I'm having trouble getting phong shading to look right. I'm pretty sure there's something wrong with either my OpenGL calls, or the way I'm loading my normals, but I guess it could be something else since 3D graphics and Assimp are both still very new to me. When trying to load .obj/.mtl files, the problems I'm seeing are:
The models seem to be lit too intensely (less phong-style and more completely washed out, too bright).
Faces that are lit seem to be lit equally all over (with the exception of a specular highlight showing only when the light source position is moved to be practically right on top of the model)
Because of problems 1 and 2, spheres look very wrong:
picture of sphere
And things with larger faces look (less-noticeably) wrong too:
picture of cube
I could be wrong, but to me this doesn't look like proper phong shading.
Here's the code that I think might be relevant (I can post more if necessary):
file: assimpRenderer.cpp
#include "assimpRenderer.hpp"
namespace def
{
assimpRenderer::assimpRenderer(std::string modelFilename, float modelScale)
{
initSFML();
initOpenGL();
if (assImport(modelFilename)) // if modelFile loaded successfully
{
initScene();
mainLoop(modelScale);
shutdownScene();
}
shutdownOpenGL();
shutdownSFML();
}
assimpRenderer::~assimpRenderer()
{
}
void assimpRenderer::initSFML()
{
windowWidth = 800;
windowHeight = 600;
settings.majorVersion = 3;
settings.minorVersion = 3;
app = NULL;
shader = NULL;
app = new sf::Window(sf::VideoMode(windowWidth,windowHeight,32), "OpenGL 3.x Window", sf::Style::Default, settings);
app->setFramerateLimit(240);
app->setActive();
return;
}
void assimpRenderer::shutdownSFML()
{
delete app;
return;
}
void assimpRenderer::initOpenGL()
{
GLenum err = glewInit();
if (GLEW_OK != err)
{
/* Problem: glewInit failed, something is seriously wrong. */
std::cerr << "Error: " << glewGetErrorString(err) << std::endl;
}
// check the OpenGL context version that's currently in use
int glVersion[2] = {-1, -1};
glGetIntegerv(GL_MAJOR_VERSION, &glVersion[0]); // get the OpenGL Major version
glGetIntegerv(GL_MINOR_VERSION, &glVersion[1]); // get the OpenGL Minor version
std::cout << "Using OpenGL Version: " << glVersion[0] << "." << glVersion[1] << std::endl;
return;
}
void assimpRenderer::shutdownOpenGL()
{
return;
}
void assimpRenderer::initScene()
{
// allocate heap space for VAOs, VBOs, and IBOs
vaoID = new GLuint[scene->mNumMeshes];
vboID = new GLuint[scene->mNumMeshes*2];
iboID = new GLuint[scene->mNumMeshes];
glClearColor(0.4f, 0.6f, 0.9f, 0.0f);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
glEnable(GL_CULL_FACE);
shader = new Shader("shader.vert", "shader.frag");
projectionMatrix = glm::perspective(60.0f, (float)windowWidth / (float)windowHeight, 0.1f, 100.0f);
rot = 0.0f;
rotSpeed = 50.0f;
faceIndex = 0;
colorArrayA = NULL;
colorArrayD = NULL;
colorArrayS = NULL;
normalArray = NULL;
genVAOs();
return;
}
void assimpRenderer::shutdownScene()
{
delete [] iboID;
delete [] vboID;
delete [] vaoID;
delete shader;
}
void assimpRenderer::renderScene(float modelScale)
{
sf::Time elapsedTime = clock.getElapsedTime();
clock.restart();
if (rot > 360.0f)
rot = 0.0f;
rot += rotSpeed * elapsedTime.asSeconds();
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
viewMatrix = glm::translate(glm::mat4(1.0f), glm::vec3(0.0f, -3.0f, -10.0f)); // move back a bit
modelMatrix = glm::scale(glm::mat4(1.0f), glm::vec3(modelScale)); // scale model
modelMatrix = glm::rotate(modelMatrix, rot, glm::vec3(0, 1, 0));
//modelMatrix = glm::rotate(modelMatrix, 25.0f, glm::vec3(0, 1, 0));
glm::vec3 lightPosition( 0.0f, -100.0f, 0.0f );
float lightPositionArray[3];
lightPositionArray[0] = lightPosition[0];
lightPositionArray[1] = lightPosition[1];
lightPositionArray[2] = lightPosition[2];
shader->bind();
int projectionMatrixLocation = glGetUniformLocation(shader->id(), "projectionMatrix");
int viewMatrixLocation = glGetUniformLocation(shader->id(), "viewMatrix");
int modelMatrixLocation = glGetUniformLocation(shader->id(), "modelMatrix");
int ambientLocation = glGetUniformLocation(shader->id(), "ambientColor");
int diffuseLocation = glGetUniformLocation(shader->id(), "diffuseColor");
int specularLocation = glGetUniformLocation(shader->id(), "specularColor");
int lightPositionLocation = glGetUniformLocation(shader->id(), "lightPosition");
int normalMatrixLocation = glGetUniformLocation(shader->id(), "normalMatrix");
glUniformMatrix4fv(projectionMatrixLocation, 1, GL_FALSE, &projectionMatrix[0][0]);
glUniformMatrix4fv(viewMatrixLocation, 1, GL_FALSE, &viewMatrix[0][0]);
glUniformMatrix4fv(modelMatrixLocation, 1, GL_FALSE, &modelMatrix[0][0]);
glUniform3fv(lightPositionLocation, 1, lightPositionArray);
for (unsigned int i = 0; i < scene->mNumMeshes; i++)
{
colorArrayA = new float[3];
colorArrayD = new float[3];
colorArrayS = new float[3];
material = scene->mMaterials[scene->mNumMaterials-1];
normalArray = new float[scene->mMeshes[i]->mNumVertices * 3];
unsigned int normalIndex = 0;
for (unsigned int j = 0; j < scene->mMeshes[i]->mNumVertices * 3; j+=3, normalIndex++)
{
normalArray[j] = scene->mMeshes[i]->mNormals[normalIndex].x; // x
normalArray[j+1] = scene->mMeshes[i]->mNormals[normalIndex].y; // y
normalArray[j+2] = scene->mMeshes[i]->mNormals[normalIndex].z; // z
}
normalIndex = 0;
glUniformMatrix3fv(normalMatrixLocation, 1, GL_FALSE, normalArray);
aiColor3D ambient(0.0f, 0.0f, 0.0f);
material->Get(AI_MATKEY_COLOR_AMBIENT, ambient);
aiColor3D diffuse(0.0f, 0.0f, 0.0f);
material->Get(AI_MATKEY_COLOR_DIFFUSE, diffuse);
aiColor3D specular(0.0f, 0.0f, 0.0f);
material->Get(AI_MATKEY_COLOR_SPECULAR, specular);
colorArrayA[0] = ambient.r; colorArrayA[1] = ambient.g; colorArrayA[2] = ambient.b;
colorArrayD[0] = diffuse.r; colorArrayD[1] = diffuse.g; colorArrayD[2] = diffuse.b;
colorArrayS[0] = specular.r; colorArrayS[1] = specular.g; colorArrayS[2] = specular.b;
// bind color for each mesh
glUniform3fv(ambientLocation, 1, colorArrayA);
glUniform3fv(diffuseLocation, 1, colorArrayD);
glUniform3fv(specularLocation, 1, colorArrayS);
// render all meshes
glBindVertexArray(vaoID[i]); // bind our VAO
glDrawElements(GL_TRIANGLES, scene->mMeshes[i]->mNumFaces*3, GL_UNSIGNED_INT, 0);
glBindVertexArray(0); // unbind our VAO
delete [] normalArray;
delete [] colorArrayA;
delete [] colorArrayD;
delete [] colorArrayS;
}
shader->unbind();
app->display();
return;
}
void assimpRenderer::handleEvents()
{
sf::Event event;
while (app->pollEvent(event))
{
if (event.type == sf::Event::Closed)
{
app->close();
}
if ((event.type == sf::Event::KeyPressed) && (event.key.code == sf::Keyboard::Escape))
{
app->close();
}
if (event.type == sf::Event::Resized)
{
glViewport(0, 0, event.size.width, event.size.height);
}
}
return;
}
void assimpRenderer::mainLoop(float modelScale)
{
while (app->isOpen())
{
renderScene(modelScale);
handleEvents();
}
}
bool assimpRenderer::assImport(const std::string& pFile)
{
// read the file with some example postprocessing
scene = importer.ReadFile(pFile,
aiProcess_CalcTangentSpace |
aiProcess_Triangulate |
aiProcess_JoinIdenticalVertices |
aiProcess_SortByPType);
// if the import failed, report it
if (!scene)
{
std::cerr << "Error: " << importer.GetErrorString() << std::endl;
return false;
}
return true;
}
void assimpRenderer::genVAOs()
{
int vboIndex = 0;
for (unsigned int i = 0; i < scene->mNumMeshes; i++, vboIndex+=2)
{
mesh = scene->mMeshes[i];
indexArray = new unsigned int[mesh->mNumFaces * sizeof(unsigned int) * 3];
// convert assimp faces format to array
faceIndex = 0;
for (unsigned int t = 0; t < mesh->mNumFaces; ++t)
{
const struct aiFace* face = &mesh->mFaces[t];
std::memcpy(&indexArray[faceIndex], face->mIndices, sizeof(float) * 3);
faceIndex += 3;
}
// generate VAO
glGenVertexArrays(1, &vaoID[i]);
glBindVertexArray(vaoID[i]);
// generate IBO for faces
glGenBuffers(1, &iboID[i]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, iboID[i]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLuint) * mesh->mNumFaces * 3, indexArray, GL_STATIC_DRAW);
// generate VBO for vertices
if (mesh->HasPositions())
{
glGenBuffers(1, &vboID[vboIndex]);
glBindBuffer(GL_ARRAY_BUFFER, vboID[vboIndex]);
glBufferData(GL_ARRAY_BUFFER, mesh->mNumVertices * sizeof(GLfloat) * 3, mesh->mVertices, GL_STATIC_DRAW);
glEnableVertexAttribArray((GLuint)0);
glVertexAttribPointer((GLuint)0, 3, GL_FLOAT, GL_FALSE, 0, 0);
}
// generate VBO for normals
if (mesh->HasNormals())
{
normalArray = new float[scene->mMeshes[i]->mNumVertices * 3];
unsigned int normalIndex = 0;
for (unsigned int j = 0; j < scene->mMeshes[i]->mNumVertices * 3; j+=3, normalIndex++)
{
normalArray[j] = scene->mMeshes[i]->mNormals[normalIndex].x; // x
normalArray[j+1] = scene->mMeshes[i]->mNormals[normalIndex].y; // y
normalArray[j+2] = scene->mMeshes[i]->mNormals[normalIndex].z; // z
}
normalIndex = 0;
glGenBuffers(1, &vboID[vboIndex+1]);
glBindBuffer(GL_ARRAY_BUFFER, vboID[vboIndex+1]);
glBufferData(GL_ARRAY_BUFFER, mesh->mNumVertices * sizeof(GLfloat) * 3, normalArray, GL_STATIC_DRAW);
glEnableVertexAttribArray((GLuint)1);
glVertexAttribPointer((GLuint)1, 3, GL_FLOAT, GL_FALSE, 0, 0);
delete [] normalArray;
}
// tex coord stuff goes here
// unbind buffers
glBindVertexArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
delete [] indexArray;
}
vboIndex = 0;
return;
}
}
file: shader.vert
#version 150 core
in vec3 in_Position;
in vec3 in_Normal;
uniform mat4 projectionMatrix;
uniform mat4 viewMatrix;
uniform mat4 modelMatrix;
uniform vec3 lightPosition;
uniform mat3 normalMatrix;
smooth out vec3 vVaryingNormal;
smooth out vec3 vVaryingLightDir;
void main()
{
// derive MVP and MV matrices
mat4 modelViewProjectionMatrix = projectionMatrix * viewMatrix * modelMatrix;
mat4 modelViewMatrix = viewMatrix * modelMatrix;
// get surface normal in eye coordinates
vVaryingNormal = normalMatrix * in_Normal;
// get vertex position in eye coordinates
vec4 vPosition4 = modelViewMatrix * vec4(in_Position, 1.0);
vec3 vPosition3 = vPosition4.xyz / vPosition4.w;
// get vector to light source
vVaryingLightDir = normalize(lightPosition - vPosition3);
// Set the position of the current vertex
gl_Position = modelViewProjectionMatrix * vec4(in_Position, 1.0);
}
file: shader.frag
#version 150 core
out vec4 out_Color;
uniform vec3 ambientColor;
uniform vec3 diffuseColor;
uniform vec3 specularColor;
smooth in vec3 vVaryingNormal;
smooth in vec3 vVaryingLightDir;
void main()
{
// dot product gives us diffuse intensity
float diff = max(0.0, dot(normalize(vVaryingNormal), normalize(vVaryingLightDir)));
// multiply intensity by diffuse color, force alpha to 1.0
out_Color = vec4(diff * diffuseColor, 1.0);
// add in ambient light
out_Color += vec4(ambientColor, 1.0);
// specular light
vec3 vReflection = normalize(reflect(-normalize(vVaryingLightDir), normalize(vVaryingNormal)));
float spec = max(0.0, dot(normalize(vVaryingNormal), vReflection));
if (diff != 0)
{
float fSpec = pow(spec, 128.0);
// Set the output color of our current pixel
out_Color.rgb += vec3(fSpec, fSpec, fSpec);
}
}
I know it's a lot to look through, but I'm putting most of the code up so as not to assume where the problem is.

Answer 1

Are you doing the right thing for the normal matrix? This looks quite bizarre to me.
for (unsigned int j = 0; j < scene->mMeshes[i]->mNumVertices * 3; j+=3, normalIndex++)
{
normalArray[j] = scene->mMeshes[i]->mNormals[normalIndex].x; // x
normalArray[j+1] = scene->mMeshes[i]->mNormals[normalIndex].y; // y
normalArray[j+2] = scene->mMeshes[i]->mNormals[normalIndex].z; // z
}
glUniformMatrix3fv(normalMatrixLocation, 1, GL_FALSE, normalArray);
Why does the normalMatrix have anything to do with the vertices of the mesh? It should be identical to your modelMatrix (provided that you're not doing any non-uniform scaling).