Swing Hacks

Turn the Spotlight on Swing #64

Chapter 8, Rendering

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HACK

paint( ) method of the component you want to see through the Java3D

scene is less efficient than taking a screen capture with the help of

java.awt.

Robot

; however, it is a lot easier because it works even when the

Canvas3D

has already been added to the window. This allows, for instance, changing

the texture when the window is resized and the gradient changes due to the

new dimensions.

Once the content panel has been fully drawn in

image, you must clip it to

retrieve the exact part covered by the

Canvas3D. This is done with another

BufferedImage

called

subImage

. This new picture has the same dimensions as

the 3D scene. The second step is to draw

image on subImage (without forget-

ting to change the origin of the drawing when you call

drawImage( )). When

the two last parameters of this method are both

0, the image is drawn on the

target surface with its top-left corner at the target’s top-left corner. With the

coordinates –

c3d.getX( ) and –c3d.getY( ), the pixel of image drawn at the

top-left corner of

subImage is the pixel where the Canvas3D is located on

screen. This ensures the code paints the exact part of the content panel that

lies behind the 3D scene.

Then, a

Background object is created with subImage as a texture. To achieve

this, you need to create an

ImageComponent2D from the BufferedImage—and

don’t forget to make the pixel formats compatible! Since

subImage has its

pixels stored as RGB integers, you must do the same for

ImageComponent2D. A

bounding sphere is finally attached to the background. Java3D uses this

sphere to know where the background object needs to be rendered and

where it should not be rendered. In this case, the background will appear

within a sphere of a radius of 100 units. This value is large enough to pre-

vent any rendering problem. Figure 8-11 shows the final result, with a

“transparent” 3D scene and no bugginess with pop-up menus.

—Romain Guy

H A C K

#64

Turn the Spotlight on Swing Hack #64

Users often get lost when using applications, as if they were in total

darkness. Why don’t you turn on a spotlight to show them the way?

Most applications involve a fair amount of data manipulation. The user cre-

ates, edits, deletes, and moves around data items. When the amount of data

becomes important, it is vital for the user to be able to search for items eas-

ily. Yet, search result displays are often irritatingly complicated, and the

results are a pain to browse through. This hack describes how to draw a

user’s attention to only the parts of the UI you want him to look at.