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Introduction
Envelopes, envelopes, envelopes - they are everywhere in LightWave...and there still aren't enough of them. Seasoned animators want to be able to animate EVERY parameter, sometimes for no other reason than that they just want to. (You know it's true.) In some cases, though, they have a point.
LightWave users have long wanted the ability to envelope surface parameters, and have used workarounds such as surface morphing to 'solve' the problem. Realitools2 gives you a much more powerful and elegant solution. In addition, it gives you even more control than you'd have by simply having more little 'E' buttons on the surface panel, because Realitools2's Surface Envelope plug-in gives you a choice of modes like add, subtract and multiply. In addition, it gives you the ability to control both parameters and to dissolve those parameters in and out.
This is a pretty self-explanatory plug-in. An envelope controls values over time, and Surface Envelopes uses a version of the standard LightWave envelope interface. You can envelope any of the surface parameters listed, although as of this writing the glossiness control doesn't work due to limitations in the LightWave code.
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There are a few differences, one of the main ones being that the only way to create a key frame is to use the 'Create Key Frame' mouse mode and then click within the timeline. This is an inaccurate method most of the time, however because it's hard to click that mouse exactly where you want it. The best method practically is the click the mouse about where you want it, and then use the Curent Value control to fine tune. Alternately, you could create an envelope in another part of LightWave, save the envelope and then load it from the Surface Envelope panel.
Modes
When you envelope a surface parameter, you pick a 'Type' - a mode that the enevelope will be applied in. These are roughly equivilent to the modes that a paint program like Adobe Photoshop uses to combine images. To show the effect of different modes, let's animate one parameter over 30 frames. We'll pick something nice and visual - reflectivity.
First, let's look at our sphere with its reflectivity set to 50%, without using the Surface Envelope plug-in. We'll see how it looks at frames 0, 15, and 30.
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Pretty boring, huh?
Now we'll apply an envelope, and see the effects of the different modes. We'll use the same envelope with all four modes. Let's just set a simple one - at frame 0, a value of 0% and at frame 30, and a value of 50%. First, let's see the effect of Overlay mode.
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Overlay mode replaces the surface's values with what you've chosen. In this case, the reflectivity becomes 0% at frame 0, 50% at frame 30...and by extension, it's about 25% at frame 15.
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Add mode adds the envelope's values to the surface's values. In our example, at frame 0 the reflectivity value of 50% is added to the envelope value of 0%. When the computer does the complex math, it yields a value of 50% at frame 0. At frame 30, 50% is adding to 50% for a reflectivity value of 100%.
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Subtract mode (you guessed it) subtracts the envelope's value from the parameter's value. At frame 0, 50% would have 0% subtracted from it, leaving 50%. At frame 30, the envelope value of 50% would be subtracted from 50%, leaving no reflectivity on the surface.
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Multiply mode (I know it seems too easy, but keep reading) multiplies the envelope's values by the parameter's value. The only trick here is that the value multiplied might not be the value you think it is. Frame 0 is easy - 0 times anything is 0, so we multiply the envelope value of 0 at frame 0 by the parameter value to give us the reflectivity value of 0%. Now, let's look at frame 30 - you might think we'd multiply 50 times 50, to yield 2500% - but that's not correct. What is actually multiplied is 50% (the surface parameter) times .5 which equals 25%.
In other words, in multiply mode an envelope value of 50% really means .5 - the scale is different. 100% equals 1.0, 75% equals .75, and so on.
More on modes
One reason to use the add, subtract, or multiply modes is that they allow you to use textures on the surface parameter. We'll take a sphere, and add a simple fractal noise pattern to it where we alternate a dark gray (50,50,50) and a medium gray (150,150,150). Then we'll use Surface Envelope on the Color parameter, and create keyframes in the blue channel. At frame 0, we'll use a value of 0 and at frame 30, we'll use a value of 100.
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You can see that in overlay, the surface envelope completely covers up the texture pattern. In the other modes, however, the values of the envelope are applied to values of the texture. You can also acheieve similiar results by using the Dissolve function.