Rotated Blocks

The ability to rotate the coordinate system for a block is now supported in LC. Any rotation angle is allowed. This feature is useful for representing bends in interconnect structures as shown above. Blocks can be rotated around all three coordinate axes, so more complex variations are possible. Three additional fields are provided in the geometry block editing area in the Main Window to display and modify the rotation angles.

This feature can be contrasted with the Edit Transform dialog rotate function, which applies a transformation to the coordinates of the block. Since the block is aligned with the coordinate axes, only rotations which are a multiple of 90 degrees are allowed.

The rotated blocks are no longer aligned with the FD-TD mesh, and are therefore approximated via staircasing. This model was created by converting the three blocks forming the three segments of the trace into the mesh form via the Edit Convert To Mesh dialog.

If an infinitely-thin (two dimensional) block is rotated within the plane in which is lies, its meshed representation results in a staircase of 2D cells. However, if it is rotated outside of its plane, the meshed representation is the projection of the rotated block onto the plane.

This is an image visualizing the power density on the ground plane as a short pulse travels down the angled portion of the microstrip. The effect of the discontinuity is apparent as red spots on the inside corners of the bend. The effect of staircasing of the angled block is also visible.

Since rotated blocks are now supported, the Read Gerber File dialog can now successfully convert Gerber artwork files containing diagonal traces. In previous versions of LC, diagonal traces were converted into an axis-aligned bounding box and flagged in red to indicate an unsupported geometry configuration.

More pointer mode buttons have been added to the Model Viewport for block manipulation functions. Blocks can be moved, resized, and rotated with the new pointer modes.

For a move, drag the pointer in the viewport and the selected blocks are translated in the displayed dimensions (X and Y in the case of a +Z view).

To resize blocks, drag the pointer in the viewport and the selected blocks are scaled. Moving up or right grows the blocks along that axis, moving down or left shrinks them. Each block is scaled about its center.

Blocks may be rotated within the plane of the viewport to any orientation (not just 90 degree rotations, as required with the Edit Transform dialog. Each block is rotated around its center.

Blocks which have been moved or scaled in this way remain simple blocks. However, blocks which have been rotated through a pointer drag are now displayed and updated in a somewhat different manner. The Min and Max coordinates displayed in the main window editing area for a rotated block now reflect the values within the block's new coordinate system. The new coordinate system is rotated from the normal coordinate system. Thus, the axis annotations displayed in the Model Viewport are no longer correct for a rotated block. The Center and Size displayed for a rotated block work as normal.

Also note that rotated blocks can no longer be aligned with the simulation mesh, as thus the geometry approximated within a simulation via staircasing.

The default is to scale or rotate about the center of the selected blocks, which is a change from previous versions of LC. In older versions, the scale or rotate was always performed about the origin (point (0,0,0)).

The default fill pattern for materials can be set in addition to the default material color. The default fill pattern is automatically selected when the material is selected.

Materials can now be selectively imported from another model file as well, via the Select Materials From Model File button.

When you choose the model file from the Open Model file browser dialog, the file is read and a list of the materials from that file is displayed. Materials can be copied into the current model by selecting them from the list.

Sigma is defined as amount of time it takes the pulse to fall peak to 1/e (37%) of its peak value. Thus, if rise sigma and fall sigma are set to 1, then the initial and final values of the source is 37% of its peak. The default value of 3 gives short run times and acceptable error (less than 0.02% of the peak value) for many types of simulations. Larger sigma values will result in an even more accurate gaussian pulse initial and final values, at the expense of the number of time steps required during the simulation.

This diagram shows three gaussian pulse source waveforms with varying rise and fall sigma values.

All of the waveforms have 1 ns rise and fall times and start at time 0.

Layer Prefix is a prefix which is added to the name of each block created as the file is read.

Material Name is the material assigned to the blocks.

The Clip values are used to specify a rectangular clipping region. Blocks within the boundary are created, possibly by truncation at the boundary. Blocks outside of the boundary are discarded. If any field is left blank, then no clipping is done at that boundary.

The Z values specify the placement of the planar data along the Z-axis. If Z Min is equal to Z Max, then the created blocks are infinitely thin.

The Offset values are added to the (X,Y) coordinates read from the file. The offset values are added after the clipping is performed.