Applying Properties

RepTile Surfaces Expert

Overview

When modeling objects that have many small repeated structures, it may be infeasible to create the structures using TracePro or any other solid modeling program. For example, brightness-enhancing films used in flat-panel LCDs may have thousands or millions of repeated surface structure elements. The RepTile surface feature in TracePro allows you to create these objects by specifying the shape of one tile, or one column of tiles. This feature allows you to create complicated models with a great reduction in model size, audit time, and ray-trace time compared to equivalent models with solid geometry.

Specifying a RepTile surface

The process of making a RepTile surface in TracePro is similar to applying a surface property. TracePro has a database of different RepTile surface shapes and geometries, and you can define different RepTile parameters and add them to the database. The database is accessed through the RepTile Property Editor. Different tile shapes (ring, rectangular, staggered rectangular, and hexagonal) and tile geometries (conical, spherical, ellipsoidal, hip-roof, cube-corner, prism, rounded prism, and Fresnel lens) are available. In general, the geometries can be defined as either “bumps” or “holes”. Once a RepTile property is entered in the database (see “RepTile Surfaces” on page 4.40), it can be applied to a plane surface using the RepTile tab of the Apply Properties dialog box. Additional data is also needed, namely a boundary (rectangular or circular) on the plane surface within which the tiles exist, and the location of a reference tile (the (0,0) tile). These data are entered in the RepTile tab of the Apply Properties dialog box.

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FIGURE 4.31 - RepTile Dialog

TracePro permits one RepTile property per Surface. So a Block with 6 surfaces could have up to 6 RepTile properties, one on each surface.

When you apply a RepTile property to a plane surface, TracePro defines a “cell” containing the tiled space. The cell has the shape of the boundary (circular or rectangular) and a calculated depth. If the RepTile property is Parameterized the cell depth is entered in the dialog otherwise the depth of the cell is as follows:

•The depth or height, d, of the deepest geometry is calculated.

•A buffer of 0.001 mm is added to each side.

The total depth of the cell is d + 0.002 mm, and all geometry surfaces are at least 0.001 mm from the top and bottom planes that bound the cell. You must be aware of this calculated depth, because the cell must be completely contained within the object that owns the RepTile surface. If this rule is violated, incorrect rays will result. Another way to think of this is that the cell “sticks into” the surface by a distance d + 0.002 mm (this is true for both “holes” and “bumps”). There must also be a margin around the edges of the cell. That is, the cell boundary should not be

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coincident with any surface of the object in order for rays to escape. This margin can be small, e.g. 0.001 mm, but it should not be zero or errant rays will result.

FIGURE 4.32 - A completed RepTile Surface. The tiled region has a rectangular boundary, and the tiles are rectangular with conical geometry. The tile numbering increases along the x and y axes. Tiles along the local x axis are in rows, and those along the local y axis (the Up vector) are in columns.

The orientation of tiles in a RepTile surface is determined by the Tile Up Vector you enter when applying the RepTile Surface property to a surface. The direction of the Tile Up Vector defines the local y axis of the tiles, the plane normal vector defines the local z axis, and the local x axis is orthogonal to the y and z axes and forms a right-handed coordinate system. The boundary is oriented according to the Boundary Up Vector entered. The Height of the boundary is measured along the Boundary Up Vector. The width of tile shapes and geometry is the dimension along the local x axis, and the height is along the local y axis (the Tile Up vector). Depth/height of “bumps”/ “holes” is along the local z axis.

Figure 4.32 shows a rectangular plane surface with a RepTile Surface property applied to it. You specify the (x, y, z) location of the (0,0) tile. The tile numbering increases along the x and y axes. The tile directly above the (0,0) tile is (0,1), and the tile to the right of the (0,0) tile is (1,0). In general, a tile is referred to by its coordinates (nx,ny). When you select variable geometry, the geometry varies as

ny varies, so that for a given ny, all the nx tiles are the same as shown in Figure 4.32.

When you enter the coordinate of the (0,0) tile, it doesn’t have to be on the surface. If it is above or below the surface, the point will be projected onto the surface along the surface normal. If the point is outside the boundary of the

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surface, some of the tiles (or fractions of tiles) will not be used, but this is a perfectly valid way to use the RepTile Surface feature.

Depth for Parameterized Reptile

When a RepTile property is defined as Parameterized, the depth is entered in the Apply Properties Dialog. These properties allow the RepTile feature to be truncated by or immersed in the Object containing the property.

	Truncated		Top tangent
		Immersed	to surface

FIGURE 4.33 - Parameterized Spherical Bumps at three different depths.

Figure 4.33 shows an example using Spherical Geomerty for three different Boundary Depths.

•The Truncated case has a Boundary Depth less than the Geometry Depth.

•The Immersed case has a Boundary Depth greater than the Geometry Depth.

•The third case has the two depths being equal.

The horizontal line below the sphere is the Boundary surface defined by the RepTile property.

Boundary Shapes

Circular boundary

You specify a circular boundary by a center point (x, y, z) and a radius. When you specify a circular boundary, TracePro creates a disk-shaped cell to contain the tiles.

Rectangular boundary

You specify a rectangular boundary by a center point (x, y, z), Boundary Up vector, width, and height. When you specify a rectangular boundary, TracePro creates a rectangular cell to contain the tiles.

Export

The RepTile surface information can be exported to a file. TracePro provides a text format containing the a description of the property with defining data. The geometry can be exported as a 2 dimensional mask or 3 dimensional wireframe in DXF format. In all cases, the property must first be applied to a surface to enable the Export function.

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