Updating old matrix with new one using glUniformMatrix4fv()? - c++

Question

I have an issue updating the old matrix with the new one, as I am transitioning from WebGL to OpenGL, it started to get daunting when I wanted to translate the object with keys actions, the issue is that when I want to do the new translation, the new matrix should be updated and the data supplied to the vertex shader(uniform u_matrix) should be changed too, but it doesn't.
To showcase the problem, I made it simpler, I'm drawing once with a translation matrix and after sleep(2), I'm drawing once again but with a different translation matrix and sleep another 2 seconds to see the result, the problem is that the matrix is not updated at all at the second phase and there is no change at all.
The matC.translate(nb1, nb2, nb2) works well by returning a pointer to the first value of 16' value 1D array stored on stack.
#include <GL/glew.h>
#include <GL/glu.h>
#include <GL/glut.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <fstream>
#include <vector>
#include <cmath>
#include <assert.h>
#include <unistd.h>
#include "./../Matrix/main.cpp";
using namespace std;
GLuint prog_hdlr;
GLint a_position;
const int SCREEN_WIDTH = 1024;
const int SCREEN_HEIGHT = 1024;
// float * translation = matC.translation(0.2, 0, 0);
// float * rotationX;
// float * rotationY;
// float * rotationZ;
// float translate = 0.01;
// float * tab4 = matC.multiplyMatrices(tab1, tab2);
static unsigned int CompileShader(unsigned int type, const string& source) {
unsigned int id = glCreateShader(type);
cout << source.c_str() << endl;
const char * src = source.c_str();
glShaderSource(id, 1, &src, NULL);
glCompileShader(id);
int result;
glGetShaderiv(id, GL_COMPILE_STATUS, &result);
if(result == GL_FALSE) {
std::cout << "failed to compile shader" << std::endl;
GLint maxLength = 0;
glGetShaderiv(id, GL_INFO_LOG_LENGTH, &maxLength);
vector<GLchar> errorLog(maxLength);
glGetShaderInfoLog(id, maxLength, &maxLength, &errorLog[0]);
int iter;
for (vector<GLchar>::const_iterator iter = errorLog.begin(); iter != errorLog.end(); ++iter)
cout << *iter;
glDeleteShader(id);
}
return id;
}
static int CreateProgram(const string& vertexShader, const string& fragmentShader) {
unsigned int program = glCreateProgram();
unsigned int vs = CompileShader(GL_VERTEX_SHADER, vertexShader);
unsigned int fs = CompileShader(GL_FRAGMENT_SHADER, fragmentShader);
glAttachShader(program, vs);
glAttachShader(program, fs);
glLinkProgram(program);
glValidateProgram(program);
glDetachShader(program,vs);
glDetachShader(program,fs);
glDeleteShader(vs);
glDeleteShader(fs);
return program;
}
void input(GLFWwindow * window, int key, int action, int u, int i) {
// switch(key) {
// case GLFW_KEY_W : {
// translate += 0.1;
// translation = matC.translation(translate, 0, 0);
// };
// case GLFW_KEY_A : {
// };
// case GLFW_KEY_S : {
// translate -= 0.1;
// translation = matC.translation(translate, 0, 0);
// };
// case GLFW_KEY_D : {
// };
// };
}
int main(int argc, char * argv) {
glutInit(&argc, &argv);
GLFWwindow * window;
cout << glGetString(GL_VERSION) << endl;
if(!glfwInit())
return -1;
window = glfwCreateWindow(SCREEN_WIDTH, SCREEN_HEIGHT, "Triangle rendering", NULL, NULL);
if(!window) {
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
if(glewInit() != GLEW_OK) {
std::cout << "error..!!" << std::endl;
}
float positions[108] = {
-0.5f, -0.5f, 0.0f, 0.5f, 0.5f, 0.0f, -0.5f, 0.5f, 0.0f,
0.5f, 0.5f, 0.0f, -0.5f, -0.5f, 0.0f, 0.5f, -0.5f, 0.0f,
-0.5f, -0.5f, -1.0f, -0.5f, 0.5f, -1.0f, 0.5f, 0.5f, -1.0f,
0.5f, 0.5f, -1.0f, 0.5f, -0.5f, -1.0f, -0.5f, -0.5f, -1.0f,
-0.5f, -0.5f, 0.0f, -0.5f, 0.5f, 0.0f, -0.5f, 0.5f, -1.0f,
-0.5f, 0.5f, -1.0f, -0.5f, -0.5f, -1.0f, -0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f, 0.5f, 0.5f, -1.0f, 0.5f, 0.5f, 0.0f,
0.5f, 0.5f, -1.0f, 0.5f, -0.5f, 0.0f, 0.5f, -0.5f, -1.0f,
-0.5f, 0.5f, 0.0f, 0.5f, 0.5f, -1.0f, -0.5f, 0.5f, -1.0f,
0.5f, 0.5f, -1.0f, -0.5f, 0.5f, 0.0f, 0.5f, 0.5f, 1.0f,
-0.5f, -0.5f, 0.0f, -0.5f, -0.5f, -1.0f, 0.5f, -0.5f, -1.0f,
0.5f, -0.5f, -1.0f, 0.5f, -0.5f, 1.0f, -0.5f, -0.5f, 0.0f
};
float colors[108] = {
1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f,
1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f,
0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f,
1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f,
1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f,
0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f,
0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f,
1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f,
1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 1.0f,
};
string vertexShader = R"(
#version 130
attribute vec4 a_position;
attribute vec3 a_color;
varying vec3 v_color;
uniform mat4 u_matrix;
void main() {
mat4 a_matrix;
a_matrix = mat4(1.0f);
vec4 pos = u_matrix*a_position;
gl_Position = vec4(pos.xyz, 1.0);
v_color = a_color;
}
)";
string fragmentShader = R"(
#version 130
varying vec3 v_color;
void main() {
gl_FragColor = vec4(v_color, 1.0);
}
)";
unsigned int program = CreateProgram(vertexShader, fragmentShader);
glUseProgram(program);
glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
GLint attributePositionLocation = glGetAttribLocation(program, "a_position");
GLint uniformMatrixLocation = glGetUniformLocation(program, "u_matrix");
GLint attributeColorLocation = glGetAttribLocation(program, "a_color");
unsigned int buffer;
glGenBuffers(1, &buffer);
glBindBuffer(GL_ARRAY_BUFFER, buffer);
glBufferData(GL_ARRAY_BUFFER, 108*sizeof(float), positions, GL_STATIC_DRAW);
glEnableVertexAttribArray(attributePositionLocation);
glVertexAttribPointer(attributePositionLocation, 3, GL_FLOAT, GL_FALSE, 0, NULL);
unsigned int bufferColor;
glGenBuffers(1, &bufferColor);
glBindBuffer(GL_ARRAY_BUFFER, bufferColor);
glBufferData(GL_ARRAY_BUFFER, 108*sizeof(float), colors, GL_STATIC_DRAW);
glEnableVertexAttribArray(attributeColorLocation);
glVertexAttribPointer(attributeColorLocation, 3, GL_FLOAT, GL_FALSE, 0, NULL);
glfwSetKeyCallback(window, input);
// while(!glfwWindowShouldClose(window)) {
// glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// glUniformMatrix4fv(uniformMatrixLocation, 1, GL_FALSE, translation);
// glDrawArrays(GL_TRIANGLES, 0, 36);
// glfwSwapBuffers(window);
// glfwPollEvents();
// }
Matrix matC = Matrix();
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUniformMatrix4fv(uniformMatrixLocation, 1, GL_FALSE, matC.translation(0.5, 0.5, 0));
glDrawArrays(GL_TRIANGLES, 0, 36);
glfwSwapBuffers(window);
glfwPollEvents();
sleep(2);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUniformMatrix4fv(uniformMatrixLocation, 1, GL_FALSE, matC.translation(-0.5, -0.5, 0));
glDrawArrays(GL_TRIANGLES, 0, 36);
glfwSwapBuffers(window);
glfwPollEvents();
sleep(2);
glfwTerminate();
return 0;
}
In WebGL it works perfectly:
function drawScene(gl) {
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
gl.uniformMatrix4fv(whateverMatrixLocation, false, whateverMatrix);
gl.drawArrays(gl.TRIANGLES, 0, whateverNumber);
requestAnimationFrame(drawScene.bind(this, gl));
}
What I am doing wrong? I'm using GLSL version 1.3...?
EDIT:
class Matrix {
public:
Matrix() {};
static float * translation(float x, float y, float z) {
static float tab[16] = {
1, 0, 0, 0,
0, 1, 0, 0,
0, 0, 1, 0,
x, y, z, 1
};
return tab;
}
}

Answer 1

The static initializer only runs once, not each time through the function. You can switch to std::array & assign new values each time through:
class Matrix
{
public:
float* translation( float x, float y, float z )
{
static std::array< float, 16 > tab;
tab =
{
1, 0, 0, 0,
0, 1, 0, 0,
0, 0, 1, 0,
x, y, z, 1
};
return tab.data();
}
};
Or use GLM :)