How do I get my OpenGL camera to point downwards? - opengl

Question

I am trying to integrate 2 programs together.
One has a planet system (with moving cubes)
The other has code for a moving camera. It can also pan around
I have managed to put both of them together. The view of the planet system can be toggled to show
Perspective view (when '1' is pressed)
Top-view (when '2' is pressed)
I am having problems with my top-view (when 2 is pressed). It is not pointing at the planet system. It is right above the planets but not looking downwards. I want to point the camera downwards such that it looks like this
I have unsuccessfully been playing with this section of code (below) to get the camera to look down. More specifically, the coordinates in the g_camera.setViewMatrix function.
// render from top view
else if (key == GLFW_KEY_2 && action == GLFW_PRESS) {
cout << "Top-View" << endl << endl;
// set camera's view matrix
g_camera.setViewMatrix(glm::vec3(0, 15, 0), glm::vec3(0, 0, 0), glm::vec3(1, 0, 0));
//g_viewMatrix = glm::lookAt(glm::vec3(0, 15, 0), glm::vec3(0, 0, 0), glm::vec3(1, 0, 0));
render_scene();
}
Before I integrated the camera code, I used this look at function.
g_viewMatrix = glm::lookAt(glm::vec3(0, 15, 0), glm::vec3(0, 0, 0), glm::vec3(1, 0, 0));
However, when I plugged these same vectors for the g_camera.setViewMatrix function, it did not point in the same direction.
Another problem I have:
The red oval is actually a circle. How do I get it to appear as a circle instead of an oval? I integrated the code for the circle from another program. In that program, it was a perfect circle.
Here is my code
#include <cstdio> // for C++ i/o
#include <iostream>
#include <string>
#include <cstddef>
using namespace std; // to avoid having to use std::
#define GLEW_STATIC // include GLEW as a static library
#include <GLEW/glew.h> // include GLEW
#include <GLFW/glfw3.h> // include GLFW (which includes the OpenGL header)
#include <glm/glm.hpp> // include GLM (ideally should only use the GLM headers that are actually used)
#include <glm/gtx/transform.hpp>
using namespace glm; // to avoid having to use glm::
#include "shader.h"
#include "camera.h"
#define PI 3.14159265
#define MAX_SLICES 50
#define MIN_SLICES 8
#define MAX_VERTICES (MAX_SLICES+2)*3 // a triangle fan should have a minimum of 3 vertices
#define CIRCLE_RADIUS 3.0
#define WINDOW_WIDTH 1500
#define WINDOW_HEIGHT 800
// struct for vertex attributes
struct Vertex
{
GLfloat position[3];
GLfloat color[3];
};
// global variables
GLfloat g_vertices_circle[MAX_VERTICES] = {
0.0f, 0.0f, 0.0f, // try adjusting this value to get rid of red line
0.0f, 0.0f, 0.0f
};
GLfloat g_colors_circle[MAX_VERTICES] = {
1.0f, 0.0f, 0.0f,
1.0f, 0.0f, 0.0f
};
GLuint g_slices = MAX_SLICES; // number of circle slices
Vertex g_vertices[] = {
// vertex 1
-0.5f, 0.5f, 0.5f, // position
1.0f, 0.0f, 1.0f, // colour
// vertex 2
-0.5f, -0.5f, 0.5f, // position
1.0f, 0.0f, 0.0f, // colour
// vertex 3
0.5f, 0.5f, 0.5f, // position
1.0f, 1.0f, 1.0f, // colour
// vertex 4
0.5f, -0.5f, 0.5f, // position
1.0f, 1.0f, 0.0f, // colour
// vertex 5
-0.5f, 0.5f, -0.5f, // position
0.0f, 0.0f, 1.0f, // colour
// vertex 6
-0.5f, -0.5f, -0.5f,// position
0.0f, 0.0f, 0.0f, // colour
// vertex 7
0.5f, 0.5f, -0.5f, // position
0.0f, 1.0f, 1.0f, // colour
// vertex 8
0.5f, -0.5f, -0.5f, // position
0.0f, 1.0f, 0.0f, // colour
};
GLuint g_indices[] = {
0, 1, 2, // triangle 1
2, 1, 3, // triangle 2
4, 5, 0, // triangle 3
0, 5, 1, // ...
2, 3, 6,
6, 3, 7,
4, 0, 6,
6, 0, 2,
1, 5, 3,
3, 5, 7,
5, 4, 7,
7, 4, 6, // triangle 12
};
GLuint g_IBO = 0; // index buffer object identifier
GLuint g_VBO[3]; // vertex buffer object identifier
GLuint g_VAO[2]; // vertex array object identifier
GLuint g_shaderProgramID = 0; // shader program identifier
GLuint g_MVP_Index = 0; // location in shader
glm::mat4 g_modelMatrix[5]; // planets object model matrices
glm::mat4 g_modelMatrixCircle[5];// circle model matrices
glm::mat4 g_modelMatrixSubPlanets[5];// object matrices for sub-planets (moon, disc etc)
glm::mat4 g_viewMatrix; // view matrix
glm::mat4 g_projectionMatrix; // projection matrix
Camera g_camera; // camera
float g_orbitSpeed[5] = { 0.3f, 1.0f, 0.7f, 0.9f, 1.2f }; // for speed of rotation around sun
float g_rotationSpeed[5] = { 0.07f, 0.7f, 3.0f, 5.0f, 1.0f }; // for speed of rotation on own axis
float g_scaleSize[5] = { 0.5f, 0.5f, 0.5f, 0.5f, 0.5f }; // for scaling the orbiting planets
float g_axisOfRotation[5] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, }; // for offsetting the axis of rotation
void generate_circle()
{
float angle = PI * 2 / static_cast<float>(g_slices); // used to generate x and y coordinates
float scale_factor = static_cast<float>(WINDOW_HEIGHT) / WINDOW_WIDTH; // scale to make it a circle instead of an elipse
int index = 0; // vertex index
g_vertices_circle[3] = CIRCLE_RADIUS * scale_factor; // set x coordinate of vertex 1
// generate vertex coordinates for triangle fan
for (int i = 2; i < g_slices + 2; i++)
{
// multiply by 3 because a vertex has x, y, z coordinates
index = i * 3;
g_vertices_circle[index] = CIRCLE_RADIUS * cos(angle) * scale_factor;
g_vertices_circle[index + 1] = CIRCLE_RADIUS * sin(angle);
g_vertices_circle[index + 2] = 0.0f;
//Color for edges. See stackoverflow
g_colors_circle[index] = 1.0f;
g_colors_circle[index + 1] = 0.0f;
g_colors_circle[index + 2] = 0.0f;
// update to next angle
angle += PI * 2 / static_cast<float>(g_slices);
}
// Gets rid of line from middle of circle
g_vertices_circle[0] = g_vertices_circle[3];
g_vertices_circle[1] = g_vertices_circle[4];
g_vertices_circle[2] = g_vertices_circle[5];
}
static void init(GLFWwindow* window)
{
glClearColor(0.0, 0.0, 0.0, 1.0); // set clear background colour
glEnable(GL_DEPTH_TEST); // enable depth buffer test
// create and compile our GLSL program from the shader files
g_shaderProgramID = loadShaders("MVP_VS.vert", "ColorFS.frag");
// find the location of shader variables
GLuint positionIndex = glGetAttribLocation(g_shaderProgramID, "aPosition");
GLuint colorIndex = glGetAttribLocation(g_shaderProgramID, "aColor");
g_MVP_Index = glGetUniformLocation(g_shaderProgramID, "uModelViewProjectionMatrix");
// initialise model matrix to the identity matrix
g_modelMatrix[0] = g_modelMatrix[1] = g_modelMatrix[2] = g_modelMatrix[3] = g_modelMatrix[4] = glm::mat4(1.0f);
g_modelMatrixCircle[0] = g_modelMatrixCircle[1] = glm::mat4(1.0f);
g_modelMatrixSubPlanets[3] = glm::mat4(1.0f);;
// initialise view matrix
//g_viewMatrix = glm::lookAt(glm::vec3(10, 3, 8), glm::vec3(0, 0, 0), glm::vec3(0, 1, 0)); //perspective
// set camera's view matrix
//g_camera.setViewMatrix(glm::vec3(10, 3, 8), glm::vec3(0, 0, 0), glm::vec3(0, 1, 0));
g_camera.setViewMatrix(glm::vec3(0, 3, 14), glm::vec3(0, 0, 0), glm::vec3(0, 1, 0));
int width, height;
glfwGetFramebufferSize(window, &width, &height);
float aspectRatio = static_cast<float>(width) / height;
// set camera's projection matrix
g_camera.setProjectionMatrix(glm::perspective(45.0f, aspectRatio, 0.1f, 100.0f));
// initialise projection matrix
g_projectionMatrix = glm::perspective(45.0f, aspectRatio, 0.1f, 100.0f);
// generate identifier for VBO and copy data to GPU
glGenBuffers(1, &g_VBO[0]);
glBindBuffer(GL_ARRAY_BUFFER, g_VBO[0]);
glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertices), g_vertices, GL_STATIC_DRAW);
// generate identifier for IBO and copy data to GPU
glGenBuffers(1, &g_IBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_IBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(g_indices), g_indices, GL_STATIC_DRAW);
// generate identifiers for VAO
glGenVertexArrays(1, &g_VAO[0]);
// create VAO and specify VBO data
glBindVertexArray(g_VAO[0]);
glBindBuffer(GL_ARRAY_BUFFER, g_VBO[0]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_IBO);
// interleaved attributes
glVertexAttribPointer(positionIndex, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), reinterpret_cast<void*>(offsetof(Vertex, position)));
glVertexAttribPointer(colorIndex, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), reinterpret_cast<void*>(offsetof(Vertex, color)));
glEnableVertexAttribArray(positionIndex); // enable vertex attributes
glEnableVertexAttribArray(colorIndex);
/*------------------------Circle----------------------*/
// generate vertices of triangle fan
generate_circle();
// create VBO and buffer the data
glGenBuffers(1, &g_VBO[1]);
glBindBuffer(GL_ARRAY_BUFFER, g_VBO[1]);
glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 3 * (g_slices + 2), g_vertices_circle, GL_STATIC_DRAW);
glGenBuffers(1, &g_VBO[2]);
glBindBuffer(GL_ARRAY_BUFFER, g_VBO[2]);
glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 3 * (g_slices + 2), g_colors_circle, GL_STATIC_DRAW);
// create VAO and specify VBO data
glGenVertexArrays(1, &g_VAO[1]);
glBindVertexArray(g_VAO[1]);
glBindBuffer(GL_ARRAY_BUFFER, g_VBO[1]);
glVertexAttribPointer(positionIndex, 3, GL_FLOAT, GL_FALSE, 0, 0); // specify the form of the data
glBindBuffer(GL_ARRAY_BUFFER, g_VBO[2]);
glVertexAttribPointer(colorIndex, 3, GL_FLOAT, GL_FALSE, 0, 0); // specify the form of the data
/*----------------------------------------------------*/
glEnableVertexAttribArray(positionIndex); // enable vertex attributes
glEnableVertexAttribArray(colorIndex);
}
//Generates a random value between 0.1 and 0.9
double generateRandomFloat(float min, float max)
{
return min + static_cast <float> (rand()) / (static_cast <float> (RAND_MAX / (max - min)));
}
// function used to update the scene
static void update_scene()
{
// static variables for rotation angles
static float orbitAngle[5] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, };
static float rotationAngle[5] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };
float scaleFactor = 0.05;
orbitAngle[0] += g_orbitSpeed[0] * scaleFactor;
orbitAngle[1] += g_orbitSpeed[1] * scaleFactor;
orbitAngle[2] += g_orbitSpeed[2] * scaleFactor;
orbitAngle[3] += g_orbitSpeed[3] * scaleFactor;
orbitAngle[4] += g_orbitSpeed[4] * scaleFactor;
// update rotation angles
rotationAngle[0] += g_rotationSpeed[0] * scaleFactor;
rotationAngle[1] += g_rotationSpeed[1] * scaleFactor;
rotationAngle[2] += g_rotationSpeed[2] * scaleFactor;
rotationAngle[3] += g_rotationSpeed[3] * scaleFactor;
rotationAngle[4] += g_rotationSpeed[4] * scaleFactor;
// update model matrix (planets)
g_modelMatrix[0] = glm::rotate(rotationAngle[0], glm::vec3(0.0f, 1.0f, 0.0f));
g_modelMatrix[1] = glm::translate(glm::vec3(g_axisOfRotation[1], 0.0f, 0.0f)) //moves the axis of rotation along x-axis
* glm::rotate(orbitAngle[1], glm::vec3(0.0f, 1.0f, 0.0f))
* glm::translate(glm::vec3(2.0f, 0.0f, 0.0f))
* glm::rotate(rotationAngle[1], glm::vec3(0.0f, -1.0f, 0.0f)) //enables rotation on own axis. try comment
* glm::rotate(glm::radians(45.0f), glm::vec3(1.0f, 0.0f, 0.0f)) //rotates into a diamond shape
* glm::rotate(glm::radians(45.0f), glm::vec3(0.0f, 0.0f, 1.0f)) //rotates into a diamond shape
* glm::scale(glm::vec3(g_scaleSize[1], g_scaleSize[1], g_scaleSize[1]));
g_modelMatrix[2] = glm::translate(glm::vec3(g_axisOfRotation[2], 0.0f, 0.0f))
* glm::rotate(orbitAngle[2], glm::vec3(0.0f, -1.0f, 0.0f))
* glm::translate(glm::vec3(4.0f, 0.0f, 0.0f))
* glm::rotate(rotationAngle[2], glm::vec3(0.0f, 1.0f, 0.0f))
* glm::scale(glm::vec3(g_scaleSize[2], g_scaleSize[2], g_scaleSize[2]));
g_modelMatrix[3] = glm::translate(glm::vec3(g_axisOfRotation[3], 0.0f, 0.0f))
* glm::rotate(orbitAngle[3], glm::vec3(0.0f, 1.0f, 0.0f))
* glm::translate(glm::vec3(6.0f, 0.0f, 0.0f))
* glm::rotate(rotationAngle[3], glm::vec3(0.0f, 1.0f, 0.0f))
* glm::scale(glm::vec3(g_scaleSize[3], g_scaleSize[3], g_scaleSize[3]));
g_modelMatrix[4] = glm::translate(glm::vec3(g_axisOfRotation[4], 0.0f, 0.0f))
* glm::rotate(orbitAngle[4], glm::vec3(0.0f, -1.0f, 0.0f)) // -y changes orbit to clock-wise
* glm::translate(glm::vec3(8.0f, 0.0f, 0.0f))
* glm::rotate(rotationAngle[4], glm::vec3(0.0f, -1.0f, 0.0f))
* glm::scale(glm::vec3(g_scaleSize[4], g_scaleSize[4], g_scaleSize[4]));
// update model matrix (orbit paths ie.circles)
g_modelMatrixCircle[1] = glm::rotate(glm::radians(90.0f), glm::vec3(1.0f, 0.0f, 0.0f));
// update model matrix (mini planets eg. moon)
g_modelMatrixSubPlanets[3] = glm::translate(glm::vec3(g_axisOfRotation[3], 0.0f, 0.0f))
* glm::rotate(orbitAngle[3], glm::vec3(0.0f, 1.0f, 0.0f))
* glm::translate(glm::vec3(6.0f, 0.0f, 0.0f))
* glm::rotate(rotationAngle[3], glm::vec3(0.0f, 1.0f, 0.0f))
* glm::scale(glm::vec3(g_scaleSize[3], g_scaleSize[3], g_scaleSize[3]));
}
// function used to render the scene
static void render_scene()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // clear colour buffer and depth buffer
glUseProgram(g_shaderProgramID); // use the shaders associated with the shader program
glm::mat4 MVP = glm::mat4(1.0f); //ModelViewProjection matrix to be shared. Initialized to identity
//Circle 1
//MVP = g_projectionMatrix * g_viewMatrix * g_modelMatrixCircle[1];
MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrixCircle[1];
//MVP = g_camera.getViewMatrix() * g_modelMatrixCircle[1];
glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
glBindVertexArray(g_VAO[1]); // make VAO active
glDrawArrays(GL_LINE_LOOP, 0, g_slices + 2); // display the vertices based on the primitive type
glBindVertexArray(g_VAO[0]); // make VAO active
// Object 1
//MVP = g_projectionMatrix * g_viewMatrix * g_modelMatrix[0];
MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrix[0];
// set uniform model transformation matrix
glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0); // display the vertices based on their indices and primitive type
// Object 2
//MVP = g_projectionMatrix * g_viewMatrix * g_modelMatrix[1];
MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrix[1];
glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0); // display the vertices based on their indices and primitive type
// Object 3
//MVP = g_projectionMatrix * g_viewMatrix * g_modelMatrix[2];
MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrix[2];
glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0); // display the vertices based on their indices and primitive type
// Object 4
//MVP = g_projectionMatrix * g_viewMatrix * g_modelMatrix[3];
MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrix[3];
glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0); // display the vertices based on their indices and primitive type
// Object 5
//MVP = g_projectionMatrix * g_viewMatrix * g_modelMatrix[4];
MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrix[4];
glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0); // display the vertices based on their indices and primitive type
// Moon for Object 3
//MVP = g_projectionMatrix * g_viewMatrix * g_modelMatrixSubPlanets[3] * g_modelMatrix[4];
MVP = g_camera.getProjectionMatrix() * g_camera.getViewMatrix() * g_modelMatrixSubPlanets[3] * g_modelMatrix[4];
glUniformMatrix4fv(g_MVP_Index, 1, GL_FALSE, &MVP[0][0]);
glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0); // display the vertices based on their indices and primitive type
glFlush(); // flush the pipeline
}
static void cursor_position_callback(GLFWwindow* window, double xpos, double ypos)
{
// variables to store mouse cursor coordinates
static double previous_xpos = xpos;
static double previous_ypos = ypos;
double delta_x = xpos - previous_xpos;
double delta_y = ypos - previous_ypos;
// pass mouse movement to camera class
g_camera.updateYaw(delta_x);
g_camera.updatePitch(delta_y);
// update previous mouse coordinates
previous_xpos = xpos;
previous_ypos = ypos;
}
// key press or release callback function
static void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
// quit if the ESCAPE key was press
if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
{
// set flag to close the window
glfwSetWindowShouldClose(window, GL_TRUE);
return;
}
// render in perspective view
else if (key == GLFW_KEY_1 && action == GLFW_PRESS) {
cout << "Perspective-View" << endl << endl;
// set camera's view matrix
g_camera.setViewMatrix(glm::vec3(0, 3, 14), glm::vec3(0, 0, 0), glm::vec3(0, 1, 0));
//g_viewMatrix = glm::lookAt(glm::vec3(10, 3, 8), glm::vec3(0, 0, 0), glm::vec3(0, 1, 0));
render_scene();
}
// render from top view
else if (key == GLFW_KEY_2 && action == GLFW_PRESS) {
cout << "Top-View" << endl << endl;
// set camera's view matrix
g_camera.setViewMatrix(glm::vec3(0, 15, 0), glm::vec3(0, 0, 0), glm::vec3(1, 0, 0));
//g_viewMatrix = glm::lookAt(glm::vec3(0, 15, 0), glm::vec3(0, 0, 0), glm::vec3(1, 0, 0));
render_scene();
}
// render from eye-level view
else if (key == GLFW_KEY_3 && action == GLFW_PRESS) {
cout << "Eye-level View" << endl << endl;
// set camera's view matrix
g_camera.setViewMatrix(glm::vec3(0, 0, 10), glm::vec3(0, 0, 0), glm::vec3(0, 1, 0));
//g_viewMatrix = glm::lookAt(glm::vec3(0, 0, 10), glm::vec3(0, 0, 0), glm::vec3(0, 1, 0));
render_scene();
}
// Randomize size, orbit speed, axis rotation speed of planets
else if (key == GLFW_KEY_R && action == GLFW_PRESS) {
// Randomize planet size
g_scaleSize[1] = generateRandomFloat(0.1, 0.75);
g_scaleSize[2] = generateRandomFloat(0.1, 0.75);
g_scaleSize[3] = generateRandomFloat(0.1, 0.75);
g_scaleSize[4] = generateRandomFloat(0.1, 0.75);
// Randomize speed of rotation (on planets own axis)
g_rotationSpeed[1] = generateRandomFloat(0.1, 10.0);
g_rotationSpeed[2] = generateRandomFloat(0.1, 10.0);
g_rotationSpeed[3] = generateRandomFloat(0.1, 10.0);
g_rotationSpeed[4] = generateRandomFloat(0.1, 10.0);
// Randomize speed of rotation around sun
g_orbitSpeed[1] = generateRandomFloat(0.1, 1.2);
g_orbitSpeed[2] = generateRandomFloat(0.1, 1.2);
g_orbitSpeed[3] = generateRandomFloat(0.1, 1.2);
g_orbitSpeed[4] = generateRandomFloat(0.1, 1.2);
// Randomize offset for axis of rotation
g_axisOfRotation[1] = generateRandomFloat(-0.5, 0.5);
g_axisOfRotation[2] = generateRandomFloat(-0.5, 0.5);
g_axisOfRotation[3] = generateRandomFloat(-0.5, 0.5);
g_axisOfRotation[4] = generateRandomFloat(-0.5, 0.5);
// Display info for each planet
cout << "PLANET 1 - \tSize: " << g_scaleSize[1] << "\tSpeed: " << g_rotationSpeed[1]
<< "\tOrbit Speed: " << g_orbitSpeed[1] << "\tAxis offset: " << g_axisOfRotation[1] << endl;
cout << "PLANET 2 - \tSize: " << g_scaleSize[2] << "\tSpeed: " << g_rotationSpeed[2]
<< "\tOrbit Speed: " << g_orbitSpeed[2] << "\tAxis offset: " << g_axisOfRotation[2] << endl;
cout << "PLANET 3 - \tSize: " << g_scaleSize[3] << "\tSpeed: " << g_rotationSpeed[3]
<< "\tOrbit Speed: " << g_orbitSpeed[3] << "\tAxis offset: " << g_axisOfRotation[3] << endl;
cout << "PLANET 4 - \tSize: " << g_scaleSize[4] << "\tSpeed: " << g_rotationSpeed[4]
<< "\tOrbit Speed: " << g_orbitSpeed[4] << "\tAxis offset: " << g_axisOfRotation[4] << endl;
cout << endl;
render_scene();
}
}
// error callback function
static void error_callback(int error, const char* description)
{
cerr << description << endl; // output error description
}
int main(void)
{
GLFWwindow* window = NULL; // pointer to a GLFW window handle
glfwSetErrorCallback(error_callback); // set error callback function
// initialise GLFW
if (!glfwInit())
{
// if failed to initialise GLFW
exit(EXIT_FAILURE);
}
// minimum OpenGL version 3.3
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
// create a window and its OpenGL context
window = glfwCreateWindow(1500, 1000, "Assignment 2", NULL, NULL);
// if failed to create window
if (window == NULL)
{
glfwTerminate();
exit(EXIT_FAILURE);
}
glfwMakeContextCurrent(window); // set window context as the current context
glfwSwapInterval(1); // swap buffer interval
// initialise GLEW
if (glewInit() != GLEW_OK)
{
// if failed to initialise GLEW
cerr << "GLEW initialisation failed" << endl;
exit(EXIT_FAILURE);
}
// set key callback function
glfwSetKeyCallback(window, key_callback);
glfwSetCursorPosCallback(window, cursor_position_callback);
// use sticky mode to avoid missing state changes from polling
glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
// use mouse to move camera, hence use disable cursor mode
glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
// initialise rendering states
init(window);
// variables for simple time management
float lastUpdateTime = glfwGetTime();
float currentTime = lastUpdateTime;
// the rendering loop
while (!glfwWindowShouldClose(window))
{
currentTime = glfwGetTime();
g_camera.update(window); // update camera
// only update if more than 0.02 seconds since last update
if (currentTime - lastUpdateTime > 0.02)
{
update_scene(); // update the scene
render_scene(); // render the scene
glfwSwapBuffers(window); // swap buffers
glfwPollEvents(); // poll for events
lastUpdateTime = currentTime; // update last update time
}
}
// clean up
glDeleteProgram(g_shaderProgramID);
glDeleteBuffers(1, &g_IBO);
glDeleteBuffers(1, &g_VBO[0]);
glDeleteBuffers(1, &g_VBO[1]);
glDeleteVertexArrays(1, &g_VAO[0]);
glDeleteVertexArrays(1, &g_VAO[1]);
// close the window and terminate GLFW
glfwDestroyWindow(window);
glfwTerminate();
exit(EXIT_SUCCESS);
}
Camera.cpp
#include "Camera.h"
Camera::Camera()
{
// initialise camera member variables
mPosition = glm::vec3(0.0f, 0.0f, 1.0f);
mLookAt = glm::vec3(0.0f, 0.0f, 0.0f);
mUp = glm::vec3(0.0f, 1.0f, 0.0f);
mYaw = 0.0f;
mPitch = 0.0f;
mViewMatrix = glm::lookAt(mPosition, mLookAt, mUp);
mProjectionMatrix = glm::perspective(45.0f, 1.5f, 0.1f, 100.0f);
}
Camera::~Camera()
{}
void Camera::update(GLFWwindow* window)
{
// variables to store forward/back and strafe movement
float moveForward = 0;
float strafeRight = 0;
// update variables based on keyboard input
if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS)
moveForward += MOVEMENT_SENSITIVITY;
if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS)
moveForward -= MOVEMENT_SENSITIVITY;
if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS)
strafeRight -= MOVEMENT_SENSITIVITY;
if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS)
strafeRight += MOVEMENT_SENSITIVITY;
// rotate the respective unit vectors about the y-axis
glm::vec3 rotatedForwardVec = glm::rotateY(glm::vec3(0.0f, 0.0f, -1.0f), mYaw);
glm::vec3 rotatedRightVec = glm::rotateY(glm::vec3(1.0f, 0.0f, 0.0f), mYaw);
// rotate the rotated forward vector about the rotated right vector
rotatedForwardVec = glm::vec3(glm::rotate(mPitch, rotatedRightVec)*glm::vec4(rotatedForwardVec, 0.0f));
// update position, look-at and up vectors
mPosition += rotatedForwardVec * moveForward + rotatedRightVec * strafeRight;
mLookAt = mPosition + rotatedForwardVec;
mUp = glm::cross(rotatedRightVec, rotatedForwardVec);
// compute the new view matrix
mViewMatrix = glm::lookAt(mPosition, mLookAt, mUp);
}
void Camera::updateYaw(float yaw)
{
mYaw -= yaw * ROTATION_SENSITIVITY;
}
void Camera::updatePitch(float pitch)
{
mPitch -= pitch * ROTATION_SENSITIVITY;
}
void Camera::setViewMatrix(glm::vec3 position, glm::vec3 lookAt, glm::vec3 up)
{
mPosition = position;
mLookAt = lookAt;
mUp = up;
mViewMatrix = glm::lookAt(mPosition, mLookAt, mUp);
}
void Camera::setProjectionMatrix(glm::mat4& matrix)
{
mProjectionMatrix = matrix;
}
glm::mat4 Camera::getViewMatrix()
{
return mViewMatrix;
}
glm::mat4 Camera::getProjectionMatrix()
{
return mProjectionMatrix;
}
Camera.h
#ifndef __CAMERA_H
#define __CAMERA_H
#include <GLFW/glfw3.h> // include GLFW (which includes the OpenGL header)
#include <glm/glm.hpp> // include GLM (ideally should only use the GLM headers that are actually used)
#include <glm/gtx/transform.hpp>
#include <glm/gtx/rotate_vector.hpp>
using namespace glm; // to avoid having to use glm::
#define MOVEMENT_SENSITIVITY 0.0005f // camera movement sensitivity
#define ROTATION_SENSITIVITY 0.001f // camera rotation sensitivity
class Camera {
public:
Camera();
~Camera();
void update(GLFWwindow* window);
void updateYaw(float yaw);
void updatePitch(float pitch);
void setViewMatrix(glm::vec3 position, glm::vec3 lookAt, glm::vec3 up);
void setProjectionMatrix(glm::mat4& matrix);
glm::mat4 getViewMatrix();
glm::mat4 getProjectionMatrix();
private:
float mYaw;
float mPitch;
glm::vec3 mPosition;
glm::vec3 mLookAt;
glm::vec3 mUp;
glm::mat4 mViewMatrix;
glm::mat4 mProjectionMatrix;
};
#endif
Vertex shader
#version 330 core
// input data (different for all executions of this shader)
in vec3 aPosition;
in vec3 aColor;
// ModelViewProjection matrix
uniform mat4 uModelViewProjectionMatrix;
// output data (will be interpolated for each fragment)
out vec3 vColor;
void main()
{
// set vertex position
gl_Position = uModelViewProjectionMatrix * vec4(aPosition, 1.0);
// the color of each vertex will be interpolated
// to produce the color of each fragment
vColor = aColor;
}

Answer 1

You have to map from world coordinates to viewport cooordinates
x y z
--------
1 0 0 | x' = x
0 0 1 | y' = z
0 -1 0 | z' = -y
Use this to see the scene from above:
g_camera.setViewMatrix(glm::vec3(0, 15.0f, 0), glm::vec3(0, 0, 0), glm::vec3(0, 0, -1.0f));
To pane, zoom and orbit the view you have to set up translation and rotation matrices and you have to concatenate (multiply)
them with the view matrix.
Add members to the class Camerato store the translation and rotation angles:
glm::vec3 _move;
float _angX;
float _angY;
Adapt the method Camera::update to sum up the translation and rotation angles:
#define MOVEMENT_SENSITIVITY 0.01f
#define ZOOM_SENSITIVITY 0.1f
#define ROTATION_SENSITIVITY 1.0f
void Camera::update(GLFWwindow* window)
{
if ( glfwGetKey( window, GLFW_KEY_A ) == GLFW_PRESS ) _move[0] -= MOVEMENT_SENSITIVITY;
if ( glfwGetKey( window, GLFW_KEY_D ) == GLFW_PRESS ) _move[0] += MOVEMENT_SENSITIVITY;
if ( glfwGetKey( window, GLFW_KEY_S ) == GLFW_PRESS ) _move[1] -= MOVEMENT_SENSITIVITY;
if ( glfwGetKey( window, GLFW_KEY_W ) == GLFW_PRESS ) _move[1] += MOVEMENT_SENSITIVITY;
if ( glfwGetKey( window, GLFW_KEY_PAGE_DOWN ) == GLFW_PRESS ) _move[2] -= ZOOM_SENSITIVITY;
if ( glfwGetKey( window, GLFW_KEY_PAGE_UP ) == GLFW_PRESS ) _move[2] += ZOOM_SENSITIVITY;
if ( glfwGetKey( window, GLFW_KEY_UP ) == GLFW_PRESS ) _angX -= ROTATION_SENSITIVITY;
if ( glfwGetKey( window, GLFW_KEY_DOWN ) == GLFW_PRESS ) _angX += ROTATION_SENSITIVITY;
if ( glfwGetKey( window, GLFW_KEY_RIGHT ) == GLFW_PRESS ) _angY -= ROTATION_SENSITIVITY;
if ( glfwGetKey( window, GLFW_KEY_LEFT ) == GLFW_PRESS ) _angY += ROTATION_SENSITIVITY;
}
Note, you have to adjust the sensitivity and the buttons or even other kinds of input to your needs. To get a clearly defined behavior you should execute the update method in a time discrete process.
Set up the translation matrix and the rotation matrices in the methode Camera::getViewMatrix and concatenate them to the view matrix:
glm::mat4 Camera::getViewMatrix()
{
glm::mat4 rotX = glm::rotate( _angX * (float)PI / 180.0f, glm::vec3( mViewMatrix[0] ) );
glm::mat4 rotY = glm::rotate( _angY * (float)PI / 180.0f, glm::vec3( mViewMatrix[1] ) );
glm::mat4 trans = glm::translate( glm::mat4( 1.0 ), _move );
return trans * mViewMatrix * rotX * rotY;
}