Creating a Model class in OpenGl

Question

Hi All I am trying to create a model class in opengl and create an instance of the model class in a game. I am able to just render one object and the second object doesnt render.

I had the same problem when all of it was in the same class. I created a seperate VBO and VAO for bot the objects and the problems was solved.

Now I am trying to create a class out of it and now I am facing same problem. Since it is a class aren't separate VAO and VBO created??

My model class and game class are as below.

#include "FlatModel.h"

#include "Camera.h"

GLfloat vertices[] = {

//position              
-0.5f, -0.5f, 0.0f,   
-0.5f, 0.5f, 0.0f,   
0.5f, 0.5f, 0.0f,     
0.5f, -0.5f, 0.0f    
};

GLuint indices[] = {
// front
0, 1, 2,
0, 2, 3
};


 FlatModel::FlatModel(Camera* _camera, glm::vec3 color) {

camera = _camera;
objectColor = color;

ShaderLoader *shaderLoader = 0;
program = shaderLoader->CreateProgram("shaders/FlatModel.vs","shaders/FlatModel.fs");

glEnable(GL_DEPTH_TEST);
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);

glGenVertexArrays(1, &vao);
glBindVertexArray(vao);

glGenBuffers(1, &vbo);
glGenBuffers(1, &ebo);

glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices),  indices, GL_STATIC_DRAW);

glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid*)0);
glEnableVertexAttribArray(0);

glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
}

FlatModel::~FlatModel() {
}

void FlatModel::update(GLfloat time) {

GLint currentTimeLocation = glGetUniformLocation(program, "currentTime");
glUniform1f(currentTimeLocation, time);

GLint objectColorLoc = glGetUniformLocation(program, "objectColor");
glUniform3f(objectColorLoc, objectColor.x, objectColor.y, objectColor.z);

glm::mat4 mvp = camera->getprojectionMatrix() * camera->getViewMatrix() * model;
GLint mvpLoc = glGetUniformLocation(program, "mvp");
glUniformMatrix4fv(mvpLoc, 1, GL_FALSE, glm::value_ptr(mvp));
}


 void FlatModel::render() {

glUseProgram(this->program);
glBindVertexArray(vao);

glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
glBindVertexArray(0);

}

And here is the game class

#include "Game.h"

void Game::GameInit(){

camera = new Camera(45.0f, WIDTH, HEIGHT, 0.1f, 100.0f);
camera->setCameraSpeed(0.05f);

ground = new FlatModel(camera, glm::vec3(1.0f, 1.0f, 0.5f));
ground->setScale(glm::vec3(3.0f, 0.5f, 1.0f));
ground->setPosition(glm::vec3(0.0f, -0.5f, 0.0f));

box = new FlatModel(camera, glm::vec3(1.0f, 0.0f, 0.0f));
box->setScale(glm::vec3(1.0f, 0.5f, 1.0f));
box->setPosition(glm::vec3(0.0f, 0.5f, 0.0f));
}

void Game::GameUpdate(){

camera->update();

GLfloat currentTime = glutGet(GLUT_ELAPSED_TIME);
currentTime = currentTime / 1000;

ground->update(currentTime);
box->update(currentTime);
}

void Game::GameDraw(){

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

ground->render();
box->render();

}

Here is the output. Only the box shows and the ground doesnt.

Answer 1

You have to pass uniforms to shader, in Draw call not in Update. Because you activate your shader in Draw.

Check this example http://in2gpu.com/2015/06/04/drawing-a-cube/