{

const f32 DEG2RAD = acosf(-1.0f) / 180.0f;

f32 tangent = tanf(fov_vertical/2.0f * DEG2RAD); // Tangent of half fov vertical

f32 top = z_near * tangent; // Half height of near plane

f32 right = top * aspect_ratio; // Half width of near plane

auto proj = Matrix4(1.0f);

proj[0][0] = z_near / right;

proj[1][1] = z_near / top;

proj[2][2] = -(z_far + z_near) / (z_far - z_near);

proj[2][3] = -1;

proj[3][2] = -(2 * z_far * z_near) / (z_far - z_near);

proj[3][3] = 0;

return proj;

{

//

// Our game uses the right-handed coordinate system with x-right, y-forward. This applies to

// the models and also the camera positions. However, opengl expects a z-backward, x-right.

// Because of this, we need to swap around the axis for the rotation of the basis.

//

Matrix4 M = Matrix4(1.0f);

auto direction = _direction;

normalize_or_zero(&direction);

Vector3 right = glm::cross(_direction, up);

normalize_or_zero(&right);

up = glm::cross(right, direction);

normalize_or_zero(&up);

M[0][0] = right.x;

M[1][0] = right.y;

M[2][0] = right.z;

M[0][1] = up.x;

M[1][1] = up.y;

M[2][1] = up.z;

M[0][2] = -direction.x;

M[1][2] = -direction.y;

M[2][2] = -direction.z;

M[3][0] = -glm::dot(right, eye_pos);

M[3][1] = -glm::dot(up, eye_pos);

M[3][2] = glm::dot(direction, eye_pos);

return M;

{

f32 aspect = static_cast<f32>(render_target_width) / render_target_height;

camera->view_to_proj_matrix = make_projection_matrix(camera->z_near, camera->z_far,

aspect, camera->fov_vertical);

camera->world_to_view_matrix = make_look_at_matrix(camera->position, camera->forward_vector, axis_up);

// Refresh the camera orientation quaternion.

camera->orientation = get_orientation_from_angles(camera->theta, camera->phi);