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Earthquake SFX Challenge - Compositing

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This page shows how the various elements are being combined together, and what they are for.
The previous page shows the individual elements in isolation.

A. Main earthquake road damage - surface

This is the main part of the effect for the road surface.
4 layers are used here, numbers 4,5,6,7. These are:-

4. Tarmac surface with visible geometry based fragmentation.
5. Tarmac surface which splits, but has no fragmentation on the surface.
6. Mask which blends between '4' and '5' around the outer edges of the fragments
7. Texture based 'damage' to inner edge of tarmac fragments.

4 and 5 are both sequences which show the road tearing apart.
In 4, the road surface splits, and fragments around the edges break up and move out of place.
In 5, the road surface just splits cleanly.

4 looks too clean, but 5 has visible geometry edges away from the crack which spoil the effect.
So, 6 was used as a mask to blend between 4 and 5 near these edges. This blending helps to break up the straight lines of the geometry and makes the breakup look more convincing,

Finally, 7 is added to the result. This provides textured damage to the road surface fragments on the edges of the chasm.

The result of combining these four elements is shown below (click for larger image).

B. Edge damage texture

The damage at the edges of the main cracks is provided by a damage texture projected from above onto the geometry. It is not animated, which means that the edge damage is visible for the whole sequence, even before the damage has been caused.
The next stage of compositing fixes this by cross-fading between the composite created above, and undamaged road surface.

This uses layers 3 and 8, in addition to 'A' created above.
3 is undamaged road surface.
'A' is our main surface damage composite.
8 is an animated mask which initially covers all of the damage in A, but fades out progressively as the damage progresses down the road.

The result of this is shown below. This frame is from early in the sequence, so you can see the transition between damaged and undamaged.

C. Subsurface structure

The next step is to add in layers 1 and 2. These contain the CG elements for the subsurface under the road. Two layers have been rendered for this one element.
1 is rendered with directional shadow casting lighting. It creates a deep shadow in the chasm.
2 is rendered with a non-shadowing light from the front. This produces a fill light.
The two passes were rendered seperately to allow more control over the final lighting balance in the compositor.

A frame from this point in the composition is shown below. Compare this with the equivalent frame from the first composition 'A' above.

D. CG Car

There are two elements here, 9 and 10, for the car and its shadow on the road. Again these elements have been rendered seperately so that they can be independently adjusted in the final composite. This gives extra flexibility.

The composite now looks like this:

E. Background elements

Here, elements 11 and 12 are added in to complete the background of the shot.
11 is a chunk of the clean plate, and is used to fill in the part of the frame on the right that hasn't been reproduced in CG model.
12 provides the left hand side of the road. It is taken from the original raw footage, but distorted to follow the distortion of the road at the crack opens.
The only other change that has been made to this footage is been the application of a mask to cut out the required shape, so that it doesn't overlap the other elements composited so far.

We now have this:

F. Additional traffic elements

Finally, elements 13 and 14 are added in. These are simply a car and a van, masked out from the original footage, and now re-inserted back into the frame. The only change that has been made is that they have been moved in time to suit the shot. Because they were only moved in time, not in space, a simple mask was sufficient to seperate them from the background.

The final composite now looks like this:

I haven't yet tweaked the composites within AE, so the colour matching, etc is still not very good.
Blurring and grain/noise still needs to be added to the CG elements, and camera shake needs adding to the whole thing...

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