Adding Wakes

I have been researching and trying to make objects move in water. I knew that this could be done with fluids and particles but I have already tried to just create still water and it was just not feasible because of rendering times.

I was poking around Maya again and found the "create ripple" button. I tried to deconstruct it and work backwards to see if I could use it when trying to animate the animals through water. After further inspection I deemed this not possible as it would not look very good and not be the effect I was after.

I started to mess around with Maya again and tried creating some wakes. The wakes Maya creates automatically were far too extreme for what I was after but again I messed around with the settings. I did a really simple test with the "create ocean" button and then "create wake". I attached the wake to a small cube and then animated it to see what it would do. I used the "Preview ocean plane" to get an idea. The first result was quite shocking because of the size of the wake but then the small test that I did made me realise that this could be something that can be used for the film.



I then had to produce this on a larger scale because it was ok doing it with a small cube in a large ocean but I needed to do it in a river with a much larger object.

I went back to my river bed scene and tried to create an object and then add the wake to it. It was only a cuboid but it was about the size the ox was going to be. This was to give me an idea about how to adjust the wake to make it look like and ox was passing through the water, which are very slow and large, instead of a light small cube.

Once I had added the wake to my object I was trying to preview how the wake would react. It was not doing anything, The cuboid moved but the wake did nothing. It made no effect on the river at all. I tried turning the "Density/Voxel/Sec" setting to maximum (which is the setting I had used in the previous test to change the size of the wake) but it still did not work. It wasn't until I zoomed out a little bit that I saw a box similar to a container for fluids. I selected it and the notes explained that it basically was a container. Because it wasn't over the wake I presumed this was why the wake was not working. I tried to move the box over the wake and this did not work. I tried to scale the box so that it covered the whole scene and this did not work either. My wake would not work at all.

I was getting pretty frustrated so I thought rather than scaling up the box, why not scale down my scene. At this point the scene was about 8 times larger than the grid. I scaled down my scene so it fit onto the grid and therefore fit into the container without having to touch it and tried to add the wake again. This time it started to work. I honestly have no idea how or why this would not work before. I don't know why it would make a difference if I scaled up the container or scaled down the scene but it obviously did because it worked.

Now I could concentrate on adjusting the wake the settings. I thought about an ox and how the ox would effect the wake. It would not be a very large wake as they walk slowly through water so would not make a large impact on the water.

The settings were extremely sensitive for the wake. Even a 0.050 adjustment meant the whole scene changed when it was rendered. It would go for a massive wake to no wake at all. I was trying to think about and ox's wake but mostly, all I kept achieving was this:



And as you can see, there is no wake at all. I persevered and kept changing the settings and eventually I managed to achieve something that could be used for the ox.



The problem with this test was that the cube was going quite fast across the river. Again there was a very small wake behind it which you did not see until the cube was at least half way across. I decided to try one more time. After adjusting the settings again and again, I found it hard to get an exact wake that would work with the ox.



I think this test has been the most successful because it creates a small enough wake but it is still obvious there is one. If the cube was going slower it, the wake effect is exactly what it would look like when the ox crosses the river.

I then had to adjust the settings to create a wake for when the cat swims across the river. The cat does not start off in the river, but after getting pushed in by the rat, she has to swim to the log and then to the edge of the river.

I adjusted the settings in the same way that I did for the ox. After a while, I managed to achieve the exact wake I was after for the cat.



It has got that effect of swimming and has small and quick strokes because the cat is a lot smaller but faster so would swim faster and kick quickly giving that short flicking motion. In the tests it is the same size as the ox but in the film the ox would be much larger and the cat is much smaller but this will not be a problem as the settings will still effect the smaller object in exactly the same way as in this test.

I think if I had more time, I would do these tests again but with the actual models. I would use the ox model and the cat model and see how the wake effects work with it all animated. The problem is that none of the models are completed enough to be able to do that. Now that I have this understanding of the wakes and how to use the ocean shader, I dont think the river scenes will be such a problem anymore and I can easily transfer what I have learnt to the film. I still think some things need tweaking but I dont think there is any point trying to get this exactly perfect using the cubes when the geometry of the models will change how the water effects will look. Something that could look perfect on a cube will not look good at all when using the actual models.

I think these tests have been successful and have helped me learn. I think I underestimated how sensitive the settings can actually be. It has taken me a long time to work on these tests as my computer is not especially fast so rendering time has ben a killer. I think all the tests have helped me to understand and to improve. It has definitely given me a better understanding of the ocean shader.