DynaWave User Manual

Tutorial 3: Tricks for Water reflections
Now that you know how to operate DynaWave I will show you how you can do some tricks to enhance your water simulations. Load Tut3.scn. Load DynaWave and Select the water surface. To make the example more visible, set the amplitude to 1 and the time decay to 0.02. Uncheck the Record Keys box. Press play. You will see the effector animate and go below the water surface. A ripple will be created at the center of the water surface and it will expand towards the walls of the container. The problem here is that the ripple seems to get absorbed by the walls instead of being reflected back as it happens in real life. To solve this problem we will use a trick. First we have to create a copy of the effector along with its animation. Select the effector and go back to frame 0. Now copy the effector (ctrl-c). We need to place this new effector on the side of one of the walls, outside the water surface. But we need it to keep the same animation. So press the Path button in the trueSpace interface. Now press the Move tool button and move the effector with its path to the left. The new position of this copy has to be the same relative distance to the wall as the original effector (see image below). If you think about it, each effector will create a ripple (even when outside the water surface) which will hit the wall at the exact same time. This is what creates the effect of the ripple being reflected by the wall. Since this object is a copy of another effector we might need to refresh the effector list. So go to the effector tab and press the Refresh button. Now turn off Range Checking to allow for the effector outside the pond to affect the water surface. Also, set the Life Span to a number larger than your animation (say 200) so that the effect does not die before you can see it. Press play. This time around, when the ripple hits the left wall, the wave will bounce back towards the center of the pond. Lets copy effectors now for all the 4 walls and see how that looks. Don't forget to turn on the path tool so you move the whole animation along with the object. Your scene should look something like this: Now press the Refresh button to update the collision list. Press play in trueSpace to check that your animation is correct. If one of your effectors moves strangely it means that you forgot to move it along with its path. So delete it and make another copy and move the path with the object this time. Now we are ready to go. Start the simulation. Observe ho you get reflections from all 4 walls ! The reflections from the ripple move towards the center of the pond and give you a more realistic behavior. Things to consider: The trick outlined here does not give you the complete physical look because there are corners which interact with the water in a different way. Each wall will force you to duplicate the number of effectors thus slowing down the simulation. One thing you can do in cases where you have lots of effectors is to simulate the effector cluster reflection using a single large effector. In most cases the wall is far enough to make a single effector ripple hard to distinguish from the cluster ripple. You can use this trick to simulate lots of other situations, so be creative.

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Copyright 1998-2000 by Alain Bellon. All rights reserved.