Compositing and first shot

I was trying to find out the best way to composite the shots together. The problem that I found was that the river was created using the ocean shader that renders in mental ray, the rest of the environment needs to render in VRay to get the black outline when rendered.

To solve this issue, I tried to use render layers but that would not render the river in the correct shape, it would render the river in mental ray and the rest in VRay but it would render the square of ocean rather than the shape of the river which meant for any shot, I would have to go through and delete or mask the edges of the river so it only appeared in the black lines outlining the river shape.

The test that I was trying was to colour everything in the scene a bright lime green, just leaving the river the normal colour. Then in After Effects, I could key out the bright green colour just leaving the river. I can then render the same scene again with the correct colours in VRay and lay the river over it so it matches up perfectly.

I used out first shot as an opportunity to test this. Our first shot is an establishing shot of the environment. It has a slow zoom from a wide shot of the scene to the finish line which is the pavilion.

The environment didn't move so I cheated a little bit and rather then render a scene where nothing changes, I used a still image of our scene.

When I rendered this image, I had bookmarked the camera angle so I knew exactly where the camera was to match the animation of the river to this angle. 

I then rendered out the river animation with everything else in the scene bright green. Mental ray did not render out the trees as they had VRay Toon attached to them so they would only render in VRay.

I keyed out the green in After Effects but it still left some noise around the river. The only way I could get rid of this was to create a layer mask in After Effects as close to the river as possible to get rid of most of the noise. 

I layered this over the image but noticed that the trees were behind the river as they were part of the background. I rendered out a shot with everything else in the scene deleted apart from the trees so the trees would be on a layer by themselves. This was layered on top of the river. This was how the composited shot looked. 

I then added the zoom towards the pavilion and this was our first shot. 

The subtitles are to be added later when all the shots are finished and we are assembling the final sequence. The music and narration will be added at this point too.