Location of cube in OpenGL - c++

Question

The output of this code is 25 cubs rotating .
The problem that I'm facing is the location of each cubes I don not know how to make them be in one line , Like for example every 5 cubes in one line and so on.
Note : I have added the Positions of cubes.
glm::vec3 cubePositions[] = {
glm::vec3(0.0f, 0.0f, 0.0f),
glm::vec3(2.0f, 5.0f, -15.0f),
glm::vec3(-1.5f, -2.2f, -2.5f),
glm::vec3(-3.8f, -2.0f, -12.3f),
glm::vec3(2.4f, -0.4f, -3.5f),
glm::vec3(-1.7f, 3.0f, -7.5f),
glm::vec3(1.3f, -2.0f, -2.5f),
glm::vec3(1.5f, 2.0f, -2.5f),
glm::vec3(1.5f, 0.2f, -1.5f),
glm::vec3(-1.3f, 1.0f, -1.5f)
};
while (!glfwWindowShouldClose(mainWindow))
{
glfwPollEvents();
glClearColor(0.0f, 0.1f, 0.2f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//Camera transformation
glm::mat4 projection = glm::mat4(1.0f);
glm::mat4 view = glm::mat4(1.0f);
projection = glm::perspective(glm::radians(45.0f), (float)WIDTH / (float)HEIGHT, 0.1f, 100.0f);
view = glm::translate(view, glm::vec3(0.0f, 0.0f, -3.0f));
//Get uniform locations
GLint viewlLoc = glGetUniformLocation(ourShader.Program, "view");
glUniformMatrix4fv(viewlLoc, 1, GL_FALSE, glm::value_ptr(view));
GLint projlLoc = glGetUniformLocation(ourShader.Program, "projection");
glUniformMatrix4fv(projlLoc, 1, GL_FALSE, glm::value_ptr(projection));
// Call Shader Program
ourShader.Use();
glBindVertexArray(VAO);
for(unsigned int i = 0; i < 25; i++)
{
glm::mat4 model = glm::mat4(1.0f);
model = glm::translate(model, cubePositions[i]);
float angle = 20.0f * i;
angle = glfwGetTime() * 25.0f;
model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f));
GLint modelLoc = glGetUniformLocation(ourShader.Program, "model");
glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));
glDrawArrays(GL_TRIANGLES, 0, 36);
}
glBindVertexArray(0);
glfwSwapBuffers(mainWindow);
glfwPollEvents();
}

Answer 1

Use glm::translate to add a translation to the model matrix of each individual cube, dependent on the index of the cube. e.g.:
for(unsigned int i = 0; i < 25; i++)
{
float dist = ; // distance between the cubes
float x = (i % 5) * dist;
float y = (i / 5) * dist;
float angle = 20.0f * i;
angle = glfwGetTime() * 25.0f;
glm::mat4 model = glm::mat4(1.0f);
model = glm::translate(model, glm::vector3(x, y, 0.0f));
model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f));
GLint modelLoc = glGetUniformLocation(ourShader.Program, "model");
glUniformMatrix4fv(modelLoc, 1, GL_FALSE, glm::value_ptr(model));
glDrawArrays(GL_TRIANGLES, 0, 36);
}
Note, you've to define the distance (dist) between the cubes.
Note, the concatenation (multiplication *) of matrices is not Commutative.
If you want to rotate the entire block of cubes, then you've to do the translation before the rotation:
model = rotate * translate
Since glm::rotate respectively glm::translate, define a matrix and multiply the input matrix by the new matrix, glm::rotate has to be done before glm::translate:
glm::mat4 model = glm::mat4(1.0f);
model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f));
model = glm::translate(model, glm::vector3(x, y, 0.0f));
You can use the algorithm to calculate the cubePositions:
#include <vector>
std::vector<glm::vec3> cubePositions;
for(unsigned int i = 0; i < 25; i++)
{
float dist = 5.0f; // distance between the cubes
float x = (i % 5) * dist;
float y = (i / 5) * dist;
cubePositions.push_back(glm::vec3(x, y, 0.0f));
}