Written by Joshua Schpok
(edited and maintained by Nikolai Svakhine: svakhine@purdue.edu)
The software available at the project website was original developed to demonstrate the techniques developed in the SCA publication for SWELL. It has a rather limited set of features, and is admittedly a tutorial tool, probably not suited for real-world applications. As a consequence, parties interested in using this technology have approached me to develop more usable software.
Regardless, most queries received by our group come from film and art students looking for a quick, easy, and inexpensive way to integrate clouds into their projects. Thus, this document has been written. As this particular software is no longer updated, some bugs are also listed to help you work around them
When you begin Swell, your should be greeted with the a cloud ball. If you don't error messages will likely be displayed within the error prompt. 90% of errors are because your graphics hardware is insufficient or graphics drivers might be out-of-date. You need a graphics card that has vertex and pixel shaders. These are typically high-end model cards (GeForce FX and later). Other problems might occur if your color depth is 16 bits instead of 32 bits or you didn't unzip all of the files.
Assume everything goes right and you're greeted with the cloud ball. You move the camera around the cloud by dragging the left mouse button over the render screen.
Be aware that viewing the cloud from above does not work properly, and the shadow ends up getting drawn on top.
Shift+drag pans around the camera and Ctrl+drag zooms in and out.
Another bug in the software makes you go into zoom mode after you've release shift or ctrl, but it goes away after a drag and release.
Clouds in swell are defined by ellipsoids you position around the screen. These must reside between the two pink squares to be rendered.
To flip into the mode where you can make and shape your own cloud ellipsoids, check Volume->Primitive Type->Simulation. The initial cloud ellipsoid should go away, and have an open blue screen.
To actually make an ellipsoid, go down to the main window and hit the Move Up/Add button. This places a tiny new ellipsoid at the center of the screen. Increase the size using the Radius field, and further shape it by scaling along X, Y, Z. There is no way to tilt (rotate) the ellipsoids.
Moving the ellipsoids is a bit more tricky: by dragging the Translate buttons, you move the ellipsoids relative to the original camera position. So, if you've swung the camera around 90 degrees, X and Z axes are sort of switched.
You can continue to add more ellipsoids by clicking the Move Up/Add button, and edit previously placed ellipsoids by clicking the Move down button. This will move the cursor backwards along the creation history without forgetting the ones before it. Move Up/Add will then bring the cursor to more recent ellipsoids, or create a new one if the most recent one is selected.
Delete removes the currently selected ellipsoid.
You can disable the glowing cursor and volume bounds by unchecking “Show Particles” and “Show Bounds” Under the Volume panel.
The interface has been set up so that most of the common tweaks are in the main render window. Their function is best explained with expiriementation. Note the Quality attribute compromises system performance for image quality. It is probably useful to do an initial design at some lower level, then turn it up for the final render.
You can change the color of the background, the base cloud color, and the shadowed underside of the cloud. A color selector for each is available by clicking the correlating buttons under the “Media” panel.
Different media types are available under that which take a moment to process. Additional tweaking controls are under Texture Scale. Do not use/change the Vertex Noise checkbox.
In Swell, users can animate to (unfortunately disjoint) elements of the cloud. The first is the fuzzy texture that composes the small details of the cloud, and second are the large ellipsoids you used to construct the general shape. Animating the texture is the best way to convey prevailing winds. Moving the ellipsoids is best to morph the cloud into different shapes, and evolve structures.
These two techniques can be combined to augment the large-level movement of cloud. When the texture moves backwards against the direction of a ellipsoid, it seems as though the cloud is pushing against wind and has inertia. Conversely, if you move noise with the ellipsoid, the cloud seems to be naturally drifting with the current.
To adjust the texture movement, go to the Media Animation panel. Ignore the top three controls. You only will be working with the two trackballs and the numeric field below them.
Torque and Velocity adjusts the rotational and directional forces acting on the texture. The spinner balls above them adjusts the axis of this force. The texture jumps around a lot when you adjust either one. For a natural animations, I recommend using relatively low levels of both. Note you need much smaller values if you plan on using both forces together, as the accumulative force is exponential. It should be worth mentioning that the noise animation seems to speed up very gradually as the software continues to run.
Animating the ellipsoids themselves is a bit more tricky. Press capture to keyframe the location of all the ellipsoids. Now move them around. When you hit capture again, it will place a keyframe one second after the last keyframe. This time is adjustable via the Interval field. Make sure to adjust before you capture the keyframe. Once you've assembled a potentially impressive collection of keyframes, you can view them running by hitting the play button.
Typically, a user finds the animation not as compelling as it was designed, so fortunately, you can go back and adjust the frames by using the “Move Up” and “Move Down” buttons. They work similar to the ellipsoid creation buttons, but are jumping up and down through your chronological list of keyframes.
You might find this part of the software crashes a lot. For this reason, there's a rude and crude way to save your work on the bottom. Type in the filename and hit save. Pressing load will try to load the filename in the field. Note you can save and load files from within Swell, and there's no nice way to export them.
Here the basic operations are outlined, and some bugs are mentioned. This software does not represent a final product, as there seems to be a need for one. Hopefully this document will help you use the software meanwhile.
Should you require assistance, please send e-mail to Nikolai Svakhine (svakhine@purdue.edu)
Last Updated: September 25, 2005