# T2.5 \[opt] Pyramid and interactive rotation with keyboard
We can also draw a pyramid
## Pyramid data
```cpp
// pyramid vertex data with RGB colour components
GLfloat verts[] = {
-1.0f, 1.0f, 0.0f, // v0
0.0f, 1.0f, 0.0f, // v0 colour green
-1.0f, -1.0f, 0.0f, // v1
0.0f, 0.0f, 0.0f, // v1 colour black
1.0f, -1.0f, 0.0f, // v2
1.0f, 0.0f, 0.0f, // v2 colour red
1.0f, 1.0f, 0.0f, // v3
1.0f, 1.0f, 0.0f, // v3 colour yellow
0.0f, 0.0f, 1.0f, // v4
0.0f, 0.0f, 1.0f, // v4 colour blue
};
// indices of 6 triangles of a pyramid
GLuint indices[] = {
0, 1, 2, 0, 2, 3, //base
4, 0, 1,
4, 1, 2,
4, 2, 3,
4, 3, 0
};
```
you will get
## GLFW key\_callback
Write GLFW key call back in main.cpp to interactively change rotation angles
```cpp
float rot_x = 0;
float rot_y = 0;
void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods)
{
if (key == GLFW_KEY_LEFT ) {
rot_y -= 5.0;
} else if (key == GLFW_KEY_RIGHT /*&& action == GLFW_PRESS*/) {
rot_y += 5.0;
} if (key == GLFW_KEY_DOWN ) {
rot_x += 5.0;
} else if (key == GLFW_KEY_UP) {
rot_x -= 5.0;
}
glm::mat4 mat_scale = glm::scale(glm::vec3(0.5f, 0.5f, 0.5f));
glm::mat4 mat_rot_y = glm::rotate(glm::radians(rot_y), glm::vec3(0.0f, 1.0f, 0.0f));
glm::mat4 mat_rot_x = glm::rotate(glm::radians(rot_x), glm::vec3(1.0f, 0.0f, 0.0f));
glm::mat4 mat_modelview = mat_rot_x * mat_rot_y * mat_scale;
GLuint modelview_loc = glGetUniformLocation( shader.program, "modelview" );
glUniformMatrix4fv(modelview_loc, 1, GL_FALSE, &mat_modelview[0][0]);
}
```
## Set key\_callback
In main(), add one line after glfw window creation
```cpp
// create a GLFW window
window = glfwCreateWindow(640, 640, "Hello OpenGL 2", NULL, NULL);
glfwMakeContextCurrent(window);
// register the key event callback function
glfwSetKeyCallback(window, key_callback);
```
Now you can play rotating the pyramid with the arrow keys.
