3D Views... 1

Creating a Room View.. 1

Window Viewing Controls. 2

Controls on the Rotate Pop Up. 3

Rotate around x, y, z axes. 3

Theta, Phi, and Twist 3

Focal Length. 4

Field of View Angle. 4

Translate Principle Point 4

Near and Far Planes. 4

Graphic Aid. 5

Light Control 6

Save Frame. 8

Material Properties. 9

Clipping Planes. 11

Frame Control 13

Stereo. 14

 

3D Views

This program provides for three dimensional solid model views.To see these views you must be on a system that supports Open GL and have 24 graphics planes.Otherwise you will only be able to see wire frame.The objects seen in a 3d view are sitting in an xyz coordinate system.This is referred to as the spatial space.The X, Y, and Z axes are drawn in the view with the label of each axis at the positive end.Your viewing window is also assigned a coordinate system.The orthogonal axes are assigned the labels u, v, and w.The u axis is horizontal across your screen from left to right.The v axis points vertically upward.The w axis points out of the screen toward you, the viewer.The origin is at the center of the screen.The view is perspective in that objects further away appear smaller.The origin of the u,v,w system in the spatial system is called the principle point.Coming out along the w axis toward your eye, the eye position is called the center of perspective.The distance from the principle point to the center of perspective is the focal distance.

Creating a Room View

Display Room View Popup Tool

On the main tool bar go under the Stacked Image Sets pulldown to Display Room View.Select an image set from the option menu.Then click the mouse on an empty frame where you want to show the room view.If there are not empty frames, then make a new screen by hitting the Screen Control button to the right of your screen.Screens which do not have a button in empty frames cannot have anything deposited in those frames.This applies to the screens used to display all of the images of a stacked image set.

 

After you have selected the image set and frame, hit the Apply button.

A 3d room view

Window Viewing Controls

Around the perimeter of the 3d window are wheels to control the viewing angle and position.The wheels control:

left bottom wheel:translates the principle point along the u axis in the spatial system.The effect is that objects appear to move sideways.

middle bottom wheel:changes the focal distance.The effect is that objects appear to get larger or smaller.

right bottom wheel:rotates around the current v axis.

bottom vertical wheel:rotates around the current u axis.

middle vertical wheel:rotates around the current w axis.

top vertical wheel:translates along the v axis.


Controls on the Rotate Pop Up

3d View Rotate Control Popup

When you hit the Rotate button to the right on your screen you get more controls on a popup.

Rotate around x, y, z axes

At the top are controls for rotating the object around the X, Y, and Z axes respectively.

Theta, Phi, and Twist

On the pop up your line of sight is converted to spherical coordinates in terms of theta, the rotation around the Z axis, then phi, a rotation from the Z axis.Lastly twist is a rotation around that line of sight, and is a duplicate of the control on the room view window.The use of spherical coordinates allows for a system to specify a specific viewing direction.The order of rotation is theta, phi, and twist for computing these values.You may specify these angles in any order and you will arrive at the same vector.

 

The angles are shown in degrees.We do not show the angle values around the u or v axes because the axes themselves move and because the order by which you perform rotations will give a different result for the same angles.We do not show an angle of rotation around the x, y, or z axes for this reason also.Rotation around the u and v axis provides an intuitive system where the object always appears to rotate sideways when rotating around the v axis, or up and down when rotating around the u axis.

Focal Length

This control duplicates that on the 3d view window, middle button.The focal length is the distance from the eye to the principle point.Making the focal length longer has the effect of making the objects look smaller.The focal length is shown in centimeters.

Field of View Angle

The field of view angle is initially 25 degrees. As you increase the focal length you will see more of the object as it appears to get smaller on the screen because you are moving further away.Increasing the field of view angle also will make objects appear to get smaller.Changing the focal length changes your perspective view whereas changing your viewing angle does not.We have picked 25 degrees as a default to correspond with the perspective of your viewing a 28 cm high screen at a distance of about 60 cm.The field of view angle is shown in degrees.

Translate Principle Point

The x, y, and z translate controls allow you to move the principle point in the x,y,z object coordinates system.The principle point is the point in 3 space that you are looking at, and is dead center in the 3d frame window.The position of the principle point is shown in centimeters.The focal length is the distance from the principle point to your eye location, the center of perspective.Theta, phi, and twist rotations are around this point as well as rotations around the u and v axis.As mentioned above, you can also translate along the current u, v, and w axes.The new principle point will be reported in x,y,z coordinates.The u and v controls are on the 3d window.The w translate control is on the popup.

Near and Far Planes

For solid model drawing with Open GL, there is a near plane and far plane.Only points inside the frustum between the near and far planes are drawn.The near and far planes are computed as you move your eye location to include the objects that you are looking at.The distance is shown in centimeters from the eye location.For wire frame drawn under the X protocol, the near and far planes have no effect.

 

You can toggle off the near/far plane automatic computation if you want to specify the location of the near and far plane and not have it change as you change your viewing location.Note that as you make the focal length smaller, at some point the eye location will have to push the near and far planes further away to keep them in front of the eye location.We enforce a minimum distance of 1 cm to the near plane, and a minimum distance of 1 cm from the near plane to the far plane.

 

If you don't toggle off the automatic near/far control, then as soon as you change anything else the near and far planes will be moved.

Graphic Aid

3d View Graphic Aid Popup

The Graphic Aid will show a view of the object and your viewing frustum to further assist you in understanding where you have put your eye and the near and far planes.This view point has its own controls for its viewing location.Your eye is where the four corners of the frustum come together.

 

For further understanding you need to read the Open GL Programming Guide, ISBN 0-201-63274-8, Addison-Wesley Publishing Co., by Jackie Neider, Tom Davis, Mason Woo.


Light Control

We have provided complete control over the light model used.To understand the parameters of the Open GL light model, we refer you to the Open GL Programming Guide whose reference was given above.We have chosen defaults which should make it unnecessary for you to mess with the light model or lights.

Light Model Control

 

We have not fully supported all options for Open GL lighting.Open GL guarantees up to 8 lights supported.Here we provide control for only one default light.The position of the light here may only be specified relative to the viewer.Also at this time we do not provide for spot light control.Otherwise the lighting equation may be controlled.Normally you would only provide for a white light, but you do have the controls to make a colored light.With the light intensity popups, the top slider will set all three components of the color the same.Adjusting any of the bottom sliders will allow for controlling the red, green, and blue intensities separately.


 

Light Control Popoup

 

We did provide for two sided lighting.You select two sided lighting under the Light Model.Then for each outlined region of interest, go under Material Properties if you want to have a different color on the back side.The same applies for isosurfaces.


Save Frame

You can save the configuration of a 3d room view on an image set under the Save Frame option.Select Save Frame under the Frame pulldown on the main menu.What is saved is the point of view and the frame specific options for each object that is drawn.This includes transparency status and clipping planes.Note that the configuration of 2d images can also be saved with this tool.You will have to enter a unique name for each frame that you want to save.A separate list is kept under each stacked image set.To restore select Restore Frame.Click the mouse on an empty frame on a screen that you have created.


Material Properties

To change the reflecting properties of the objects drawn, referred to as material properties, you must go to the object's control.For region of interest contoured outlines, go to Contours and then look under Volume:

 

Contouring -> Contours -> Volume -> Volume Properties -> Material Properties

 

Isosurfaces have a similar control.

 

Color and reflectance is a global property for each object.Transparency, wire frame versus solid, etc., are frame specific and can be changed under Frame Control for that object for application in a specific frame.For more information look also in the above chapter on Outlining.

Materials Properties Popup Control

 

Clipping Planes

 

 

Clipping Plane Toolbar and Clipping Plane Control Popup

Outlined regions of interest volumes and isosurfaces may be clipped.The clipping is specific to the particular frame and is not a global property for the object.You can specify and position up to six clipping planes.Any part of the object on one side of the plane is clipped.Everything on the other side is not clipped.With six planes you can clip down to a box of interest.

 

To clip an outlined volume select clipping under the Volume pulldown on the contouring toolbar.Likewise for isosurfaces look under the IsoSurface pulldown on the isosurfaces toolbar.

 

On the clipping tool bar you can select one of six clipping planes at a time.The clipping plane control popup will allow you to position the clipping plane.

 

At the top of the popup you can turn the clipping plane on or off.By default it is off.Turn it on to position the plane.A grid representing the position of the plane will be shown.Use the Theta and Phi angle controls to rotate the plane.Phi is measured from the z axis, and theta is rotation around the z axis. The angles shown are in degrees.

Given a position, the Off Set control moves the plane in a direction perpendicular to the plane with distance shown in centimeters.

 

There is a color button that you can use to change the color of the clipping plane representation.By default, the grids will be the same color as the clipped object.

 

Because a clipping plane is specific to a frame, nothing is saved upon program termination unless saved with a frame.


 

Frame Control

Depending upon the type of 3D frame presented, there will be Frame Control pulldown menu as shown below:

 

The top choice will be and Options popup which you can use to change the background between black and white, or select stereo mode (see below).All structures that have controls for individual frames that are drawn in the frame can be selected from the list.Individual structures may typically be turned off or on, or have the transparency mode changed.The options available will vary with the type of structure, such as a region of interest outline (ROI) structure or an isosurface for two examples.On the contouring toolbar there is an option to turn off and on ROIís globally.


 

Stereo

If you have a stereo graphics card and a means of mapping the output to a left eye and right eye view, then you can view 3D room views in stereo.Use the Frame Control menu next to the room view adjusting wheels to select Option.You will get the below popup:

 

If the Enable Stereo is not grayed out, you can select stereo.The control will be grayed out if a stereo visual could not be obtained.The program will draw to a left and right eye buffer, with a shift corresponding to the distance between a personís eyes, here defaulted to 6.3 cm.You can switch the left and right eye with the Switch Eyes button.