OpenGL GLM Matrix Calculations Not Working - c++

Question

OpenGL glm calculations don't seem to work in my program. Nothing moves even when i use the glm translate function to translate the z axis with a variable every frame. Am i missing something?
main.cpp
#define GLEW_STATIC
#define NO_SDL_GLEXT
#include "glew.h"
#include <sdl.h>
#undef main
#include "SDL_opengl.h"
#include "timer.h"
#include <time.h>
#include <shader.h>
using namespace std;
#include <glm/gtc/matrix_projection.hpp>
#include <glm/gtc/matrix_transform.hpp>
using namespace glm;
unsigned int vaoID[1]; // Our Vertex Array Object
unsigned int vboID[1]; // Our Vertex Buffer Object
glm::mat4 projectionMatrix; // Store the projection matrix
glm::mat4 viewMatrix; // Store the view matrix
glm::mat4 modelMatrix; // Store the model matrix
Shader *shader; // Our GLSL shader
float ztransform(0);
bool exited(false);
SDL_Event event;
const int FRAMES_PER_SECOND = 60;
void createSquare(void) {
float* vertices = new float[18]; // Vertices for our square
vertices[0] = -0.5; vertices[1] = -0.5; vertices[2] = 0.0; // Bottom left corner
vertices[3] = -0.5; vertices[4] = 0.5; vertices[5] = 0.0; // Top left corner
vertices[6] = 0.5; vertices[7] = 0.5; vertices[8] = 0.0; // Top Right corner
vertices[9] = 0.5; vertices[10] = -0.5; vertices[11] = 0.0; // Bottom right corner
vertices[12] = -0.5; vertices[13] = -0.5; vertices[14] = 0.0; // Bottom left corner
vertices[15] = 0.5; vertices[16] = 0.5; vertices[17] = 0.0; // Top Right corner
glGenVertexArrays(1, &vaoID[0]); // Create our Vertex Array Object
glBindVertexArray(vaoID[0]); // Bind our Vertex Array Object so we can use it
glGenBuffers(1, vboID); // Generate our Vertex Buffer Object
glBindBuffer(GL_ARRAY_BUFFER, vboID[0]); // Bind our Vertex Buffer Object
glBufferData(GL_ARRAY_BUFFER, 18 * sizeof(GLfloat), vertices, GL_STATIC_DRAW); // Set the size and data of our VBO and set it to STATIC_DRAW
glVertexAttribPointer((GLuint)0, 3, GL_FLOAT, GL_FALSE, 0, 0); // Set up our vertex attributes pointer
glEnableVertexAttribArray(0); // Disable our Vertex Array Object
glBindVertexArray(0); // Disable our Vertex Buffer Object
delete [] vertices; // Delete our vertices from memory
}
void startGL()
{
SDL_Init(SDL_INIT_EVERYTHING);
SDL_SetVideoMode(800, 600, 32, SDL_OPENGL);
glewInit();
glClearColor(0.4f, 0.0f, 1.0f, 0.0f);
projectionMatrix = glm::perspective(60.0f, (float)800 / (float)600, 0.1f, 100.f); // Create our perspective projection matrix
shader = new Shader("shader.vert", "shader.frag"); // Create our shader by loading our vertex and fragment shader
createSquare();
}
void drawstuff()
{
glViewport(0, 0, 800, 600); // Set the viewport size to fill the window
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT); // Clear required buffers
viewMatrix = glm::translate(glm::mat4(1.0f), glm::vec3(0.0f, 0.0f, ztransform)); // Create our view matrix which will translate us back 5 units
modelMatrix = glm::scale(glm::mat4(1.0f), glm::vec3(0.5f)); // Create our model matrix which will halve the size of our model
shader->bind(); // Bind our shader
int projectionMatrixLocation = glGetUniformLocation(shader->id(), "projectionMatrix"); // Get the location of our projection matrix in the shader
int viewMatrixLocation = glGetUniformLocation(shader->id(), "viewMatrix"); // Get the location of our view matrix in the shader
int modelMatrixLocation = glGetUniformLocation(shader->id(), "modelMatrix"); // Get the location of our model matrix in the shader
glUniformMatrix4fv(projectionMatrixLocation, 1, GL_FALSE, &projectionMatrix[0][0]); // Send our projection matrix to the shader
glUniformMatrix4fv(viewMatrixLocation, 1, GL_FALSE, &viewMatrix[0][0]); // Send our view matrix to the shader
glUniformMatrix4fv(modelMatrixLocation, 1, GL_FALSE, &modelMatrix[0][0]); // Send our model matrix to the shader
glBindVertexArray(vaoID[0]); // Bind our Vertex Array Object
glDrawArrays(GL_TRIANGLES, 0, 6); // Draw our square
glBindVertexArray(0); // Unbind our Vertex Array Object
shader->unbind(); // Unbind our shader
}
int main (int argc, char* args[])
{
Timer fps;
startGL();
while(exited == false)
{
while( SDL_PollEvent(&event) )
{
if( event.type == SDL_QUIT )
exited = true;
}
drawstuff();
ztransform+=.1
SDL_GL_SwapBuffers();
if( fps.get_ticks() < 1000 / FRAMES_PER_SECOND )
SDL_Delay( ( 1000 / FRAMES_PER_SECOND ) - fps.get_ticks() );
}
SDL_Quit();
return 0;
}
shader.frag
#version 150 core
in vec3 pass_Color;
out vec4 out_Color;
void main(void)
{
out_Color = vec4(pass_Color, 1.0);
}
shader.vert
#version 150 core
in vec3 in_Position;
in vec3 in_Color;
out vec3 pass_Color;
void main(void)
{
gl_Position = vec4(in_Position, 1.0);
pass_Color = in_Color;
}

Answer 1

You have to apply your transformation in your vertex shader.
you should define in your vertex shader
uniform mat4 projectionMatrix;
uniform mat4 viewMatrix;
uniform mat4 modelMatrix;
And then apply these transformations to your input position (note: i may have gotten the order wrong)
gl_Position = projectionMatrix * viewMatrix * modelMatrix * vec4(in_position, 1.0);
Generally though, you would multiply the 3 matrices together in your c++ program and pass in a modelViewProjection matrix.