CODEWITHSUNDEEP
c++openglrotation
user3061694
user3061694

Reputation: 55

Create a camera that rotates around the object OpenGL C++

Im doing the exercises at the end of this tutorial: Link

However Im stuck on the "Create a camera that rotates around the object" 

( position = ObjectCenter + ( radius * cos(time), height, radius * sin(time) ) );

I've used the above code supplied to create the following rotation 

GLfloat radius = 10.0f;
position = glm::vec3(0.0f,0.0f,0.0f) + glm::vec3(radius * cos(glfwGetTime()), 0.0f, radius * sin(glfwGetTime()));

Using this the scene rotates around (0,0,0) at a distance of 10, which I thought was the centre of the cube, however it is not, so the cube flashes past the window every so often as the scene rotates.

So how exactly do I find the object centre? I don't understand from the code when I draw the cube where I tell it to centre it to.

For reference the initial position vec is

glm::vec3 position = glm::vec3( 0, 0, 5 );

Upvotes: 0

Views: 1771

Answers (1)

Dan M
Dan M

Reputation: 26

The easiest you can do is to add the following in the controls.cpp and declare it in controls.hpp

glm::vec3 *getPosition(){
    return &position;
}
void setPosition(glm::vec3 var){
    position = var;
}

Then you only must declare the following variables in the beginning of the main loop:

float rotCamera = 0.0f;
glm::vec3 origPos = *getPosition();

and add the following lines just after glfwPollEvents(); in the main loop:

// Swap buffers
glfwSwapBuffers(window);
glfwPollEvents();

//To rotate the camera through the object
if (glfwGetKey( window, GLFW_KEY_C ) == GLFW_PRESS){
    rotCamera += 0.01;
    glm::vec3 rot(cos(rotCamera) * 10.0 - origPos.x,  0, sin(rotCamera) * 10.0 - origPos.z);
    setPosition(origPos + rot);
}

Finally if you want the camera looking to the cube all time, you must change lookAt from controls.cpp to look always to the (0,0,0):

ViewMatrix       = glm::lookAt(position,           // Camera is here
                                glm::vec3( 0, 0, 0 ), //To look always to the cube
                                up                  // Head is up (set to 0,-1,0 to look upside-down)
                           );

Upvotes: 1

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