With Kdenlive we can modify the objects that appear in the scenes, for example by making a hole appear in a door, as if it had been smashed by someone with a kick or shotgun. Without really having to destroy a door.
Among the many clichés of action films is the destruction of objects. And one of the most versatile situations is the breaking of a door: in most action films and even in many comic films, at some point someone makes a hole in a door. With a kick, a punch, or a shotgun. The problem, for non-professional filmmakers, is that it is a fairly difficult effect to achieve directly in the room if you don’t have a budget. Destroying doors costs, and it is still difficult to do in reality: a fake door should be built, because a real door does not break easily like those seen in films. No actor can really punch a hole in a 3-4cm thick wooden door. And for obvious security reasons it’s not a great idea to use a loaded shotgun to seem like a real hole in a door. The most handy solution is to drill the hole digitally, so we won’t spend a single penny and we won’t put any actor at risk. The basic effect is simple, because it is based on rotoscoping to draw the hole. As a starting point we need two video clips: one will simply have to shoot the door (or possibly the wall) to break through. The other video clip must contain the actor who makes the gesture of breaking through the door, for example with a shotgun shot. The actor must be in the same position where the door is located: just open it and shoot the video, it does not matter if a piece of the door is still visible together with the actor. We will only use a small portion of this clip, there is no need to unhinge the door and remove it completely, however you will not see it in the final result. Obviously, when assembling the clip with the door closed must be placed over the clip with the actor and the door open. To open the hole in the door, simply apply the rotoscoping effect to its clip, but invert it (with the appropriate tick). In this way everything that is contained in the drawing we make will become transparent and you will be able to see the video that is underneath. Let’s draw, therefore, the outline of what the hole will be: it must not be too regular, in reality it is unlikely to make a perfectly circular hole. Then, in order not to make the hole appear at any moment, we use the keyframes of the rotoscoping effect to reshape the contours of the hole in order to make it grow gradually. In other words, at the beginning of the clip the hole must be so small that it is not visible, and within twenty frames or so it must grow to its final size. The effect will be fast, so it is not essential to be too careful about the movement you draw, the important thing is that the viewer understands that the hole has enlarged as it is normal for it to happen. Then you can add a clip of a muzzle flash, or flying wood splinters (debris) to give more realism. We thought to present the effect with a shotgun that opens a hole through a door, because it is the basic preparation on which variants can then be built. If you want to make the effect with a punch, instead of with a shotgun, just give the actor a punch in the void, then using rotoscoping to make visible not only the background but also the hand that passes through the hole. As always, you can see the example video at the following address: https://www.youtube.com/watch?v=EyFiycNvo2M
The movement of the room
To add realism to the scene we can also insert a movement: after rendering the sequence in which the actor makes the hole in the door with Kdenlive, we can import it into another Kdenlive project and superimpose it on a black clip using an Affine type transition. At that point we can enlarge the image a little: if we are making a FullHD movie we can increase its size by up to 120% without anyone noticing. Using the keyframes of the transition we can move the image up and down, left and right, in the fraction of a second in which the hole in the door appears. This will lead the public to believe that the camera was shaken by the same blow that opened the hole in the door. You can also add a slight rotation, but do not exaggerate otherwise you understand that the image is fake because the perspective is missing.
Overlay the initial clips
Let’s see how to position the clips of the door and the actor in the video tracks
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Draw the hole in the door
We use rotoscoping to draw the outline of the hole in the door
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An animation for the appearance of the hole
We make the hole appear in the door with an animation in which it grows gradually
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Add the explosion
We insert a muzzle flash to give the impression that the hole was from a rifle
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