After the applet has (finally) read in the data you will see three
images which are cross sections of a chick embyro. Each image
is surrounded by a rectangle colored red, green, & blue. These
correspond to the front, top and side views of planes through
the center of the 3D solid. When the mouse is dragged on these images
the colored cross hairs (which appear whenever the mouse is in the applet)
will move to follow the mouse. The other two images will update
so that they contain the planes indicated by the cross hairs on in the
image that the mouse is in. These three images will collectively be referred
to as the orthogonal images.
You will also see two buttons marked "Reset" and "Refresh"
as well as two check boxes marked "Depth Cue" and "Arbitrary
Image". The check boxes are to accommodate various levels of hardware
and patience. (I am not offering the thread bomb version.) By default,
neither check boxes are selected. You may want to first play around a bit
with just the orthogonal images , then the Depth Cue then the
Arb Image and finally both.
If you check the "Arb Image" box a fourth "arbitrary image"
will appear surrounded by a yellow rectangle, underlined by
a cyan line and flanked on the right by a magenta line. The cross
hairs in the orthogonal images will switch to three lines (cyan, magenta,
and yellow) emanating from your current location within the model (called
a "axis cross hair"). The behavior of the orthogonal images
is just as it was except the arbitrary plane also moves to contain the
common point of the orthogonal planes at the center of the arbitrary image.
You can also drag the mouse on the arbitrary image which does not cause
any change in the orthogonal images but does cause the arbitrary plane
and hence the cross hairs to rotate about the common point. Dragging
the mouse on the arbitrary image causes rotation of the arbitrary plane
about the point at the center of the arbitrary image.
Dragging left/right in the arbitrary image pivots the "yellow-cyan plane"
about the magenta axis.
Dragging up/down in the arbitrary image pivots the "yellow-magenta plane"
about the cyan axis.
The algorithm that responsible for translating a 2D mouse movement in to
a 3D rotation of a plane is simplistic and may not always function as expected.
When an axis-crosshair would extend beyond the edge of an image, the cross
hair is distorted instead of being clipped.
If you check the "Depth Cue" box, all three or four images of the model
are subject to being updated with information from "deeper" within the
model. The behavior of dragging on the orthogonal and arbitrary images
is still as it was, except that when the mouse button is released images
may again be updated as follows. If a pixel in the image falls beneath
a certain threshold of "brightness" the applet starts looking for
a brighter voxel in the direction (within the model) you were heading.
The applet also keeps track of how far it has looked and if it finds a
brighter voxel it darkens it proportionately to how far it had to look
before replacing the dark pixel of the original image with the color of
the found and darkened voxel.
note: deeper for arbitrary image the is the direction from your current
location along the yellow axis.