deep sea diving with bryce
This tutorial will focus on creating a believable (if not realistic) underwater scene in Bryce. The key to doing this is to create a caustic effect.

a caustic effect?
Caustics are the envelope of rays diffracted by surface defects in a material. A simple example would be the white shining light moving in stripes inside a water pool. Those are caustics caused by the uneven (rippled) surface of the water. Light gets refracted unevenly when it passes through the surface of the water and produces the caustic effect.

Before we embark on rendering this great natural effect, it is IMPORTANT to know that Bryce can't render the caustic effect natively. It has to be done through a work around technique.

getting started
Before we start to create our scene, you need the pattern of an actual water caustic to use as a gel to filter the light. This is the heart of our believable underwater scene. Dave Buckner has kindly donated two shader (.SHD) files to be used as caustic gels. Linda Ewing has also donated a PICT file which can be used as a gel also. To download a ZIP file containnig the shaders, click here. To download the PICT file, click here.

Once you have the gel, we're ready to rock!

Figure 1
Figure 1. For Jack Dawson
© Jonathan Yuen 1998.



Figure 2a
Figure 2a.


Figure 2b
Figure 2b.


Figure 3
Figure 3.


Figure 4
Figure 4.


Figure 5
Figure 5a.


Figure 5b
Figure 5b.


Figure 6
Figure 6.


Figure 7
Figure 7.


Figure 8
Figure 8. For Jack Dawson
© Jonathan Yuen 1998.
turn the light on!
This tutorial will focus on techniques to create an underwater scene as shown in Figure 1. You won't find caustic effects under 1000 feet below water surface because the light has become to dim, so keep depth in mind when adding caustics to your underwater scene. The effect is much more pronounced at shallow depths.

First, set up a scene as shown in Figure 2a and 2b. This scene is for setting up the lighting and caustic. Here is the quick set up:

Light source: There are people prefer to use sphere light source. But after some testing I found that the sphere light source tends to distort the caustic pattern at the edge and is less controllable, as shown in Figure 3. The caustic pattern shown to the left is from a sphere light source while the right is from a square light source. Both light sources contain the same settings.

Therefore I decided to use square light source. It's more predictable and easy to control. Now you need to set up a square light source; use the following settings:

Scale it so that it is big enough to project a clear caustic pattern and cover a large are. Notice the relative size of my square light source with default base terrain plane.

You should get something similar to what we see in Figure 2b.

terrains
The next step is to visualize your scene, how you are going to place your elements; the camera, the terrains and any other 3D objects. Figure 4 shows how I visualized the camera angle for my underwater scene.

Next part - put in the rocks. Here you can do whatever you want with the rocks. For mine, I use default generated terrain and start to modify it in the Terrain Editor, as shown in Figure 5a.

Here is editing process:

Why do we need some basic noise (it's really annoying in most instances)? Rocks that have been buried under the sea for millennia are sure to be covered with various corals, plants and other shell artifacts. The basic noise will provide a natural looking roughness, when applied with the right texture.

Figure 5b show my terrain transformation in the scene. I applied the same philosophy to other terrains.

terrain texture
I use a texture called Desert Rock which comes with Bryce under the Planes and Terrains section of the material library. I don't care much about what the texture was originally designed for, if it looks good in my scene then I use it.

Figure 6 shows the texture, but the scene doesn't look very underwater-like yet - we need to create atmosphere.

atmosphere
Here is the quick rule I developed during my experimentation with underwater scenes.

Here is the set up for my scene, continuing from the base set up in figure 2a. That's it. Figure 7 shows the effects of these settings.

NOTE : I am only able to show you the complete scene with all terrain objects in Figure 8. This is because the final BRC file I saved for my scene is corrupted (many thanks to Bryce for this). Therefore I am only able to show you partially complete terrain objects up to Figure 7. It's good I always save multiple files for different versions. I am sorry for any inconvenience.

This tutorial is applicable to Bryce on both Mac and Windows platform. Although Bryce 2 was used this tutorial will work just fine using Bryce 3D.

Here are a few resources that you might find interesting if you want to delve more into the caustic subject, courtesy of Stefan Wolfrum.


Jonathan Yuen Kok Hong is currently studying graphic design at LimKokWing Institute of Creative Technology, a design and multimedia learning center in Malaysia and has been using Bryce for around 1 year. You can contact him by email at jykh@pc.jaring.my.


Editor's Note (L. A. Ewing): There is an alternate method of creating a caustic effect in your scenes that is well worth mentioning. The gel method is very effective for close up scenes. In a large scale scenes, though, the pattern created by placing the gel on a light source will become becomes larger with distance from the light source as the light spreads out. In nature it should appear to be getting smaller farther away from the viewer.

Set up your terrain following all of Jonathan's suggestions "except" for atmospheric effects, in this method you will use the sun as the light source. You may want to give the sun a blue or green tint. Be sure to set the shadows to 70 or less, you would not expect to see hard edged shadows under water. As you can see I used a greenish gray shadow color slightly darker than my fog color.

Figure 1

Create a pict square to apply your caustic pict to as a 2-D material. Do not select infinite plane, that stretches the pattern too much. Increase the size of the pict square to cover the extent of your scene and let it sit just above the scene but out of the camera's view.

Figure 2

For this image I let the pict drive the amount of Ambience and difusion and used a pale turquiose in the color channels. After some experimantation I found a value of 50 in the transparency worked best with this particular pict. From this point you will have to do some experimenting with the alpha channel, transparency and the size of the tiling to get the pict to cast the caustic shadow that best suits your own particular image.

Figure 3Figure 4



Linda Ewing is Staff Editor of Visual Magic Magazine. She can be reached by email at linda@visualmagic.awn.com.


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