Apply Special Effects - JavaFX: Developing Rich Internet Applications - page 163

Let's dissect what's taking place here. First, gradients do not operate on the
effect instance variable. Rather, they are assigned to the content's fill
instance variable. As mentioned, gradients are not part of the javafx.scene.effect
package, but instead they belong to javafx.scene.paint .
The stops variable is a sequence used for defining the overall gradient effect.
Within the sequence, a series of Stop instances are used to describe individual
transitions. Its offset variable, ranging in value from 0 to 1, describes where,
within the content, this gradient should be placed, 0.0 being the beginning of the
content, 1.0 being the end, 0.33 being approximately a third of the way in, and so
on. Alongside the offset variable, a Stop instance should also specify the
color too. In our preceding example, we, in effect, define the simplest of transi-
tions, a beginning Stop (offset is set to 0.0) with a white color, and an end Stop
(offset 1.0) set to black. With this information, the JavaFX runtime will fill in the
content interpolating all of the colors in between the stops.
Lastly, in our example, the gradient was defined with the proportional variable
set to true. By doing so, the start and end coordinates are defined relative to the
shape where, again, 0.0 specifies the beginning of the shape, 1.0 specifies the
end. By setting proportional to false instead, the start and end points would
have to be defined in absolute pixels.
LinearGradient
Sticking with our 3D theme, gradients, among many other uses, could be
employed to add perspective to content. Let's see how a LinearGradient can be
applied to an ordinary shape to make it look more realistic. First, we'll combine
two simple shapes together, a triangle and an ellipse, to create a cone. Figure
6.10 displays the particulars; later on we'll supply the complete code.
The resulting cone uses a class called ShapeIntersect , which is part of the
javafx.scene.shape package, to construct one logical shape from a number of
previously independent ones. The ShapeIntersect a[] instance variable forms
a union of the shapes included in the sequence—in this case a triangle and an
ellipse—while the b[] sequence (not used in this example) could be used to add
additional shapes that are intersected with a[] to form yet a more complex shape.
The big advantage of using ShapeIntersect here is that you can apply an effect
to the entire object, rather than having to do so on each individual component.