ScreenToWorldPoint issue

Hello again,

I have a perspective camera and I want to use the mouse to move some 3D elements in the scene.
The problem I have is ScreenToWorldPoint() which return a Vector3 considering also Z coord.
What I want is to move the object only on X and Y axis according to mouse movement and keeping Z as is.

How to deal with that?

If your object is at z==0, then you need to use the negative distance of the camera. So, if the camera z pos == -10, then depth==10 in the ScreenToWorldPoint(). If the object is placed at z==-5, then the depth is 5.

Vector3 ScreenToPlanePos(Camera* camera, const Vector2& screenPos, const Plane& plane)
{
    const Vector3 camPos{ camera->GetNode()->GetWorldPosition() };
    const float signedDistance{ plane.Distance(camPos) };
    const float distance{ Abs(signedDistance) };
    const Vector3 normal{ signedDistance > 0.f ? -plane.normal_ : plane.normal_ };
    const Vector3 direction{ camera->GetScreenRay(screenPos).direction_ };
    const float angle{ direction.Angle(normal) };
    const float cos{ Cos(angle) };

    return camPos + direction * distance / (cos == 0.f ? M_EPSILON : cos);
}

(result - camPosition).DotProduct(camDirection) > 0.f

or

Plane{ camDirection, camPosition }.Distance(result) > 0.f

…should return true for positions in front of the camera and false for values you’d want to ignore.

Also, I forgot about Ray::HitDistance, which makes all this a lot more elegant and concise:

Vector3 Camera::ScreenToPlanePos

(const Vector2& screenPos, const Plane& plane) const
{
    const Ray ray{ GetScreenRay(screenPos) };
    const float distance{ ray.HitDistance(plane) };

    if (distance == M_INFINITY)
        return Vector3::ONE * M_INFINITY;

    return ray.origin_ + ray.direction_ * distance;
}

Making of course result.x_ != M_INFINITY your new filter.