Source Radial
The Source Radial is a flat, rectangular or elliptical shape that emits rays into a hemisphere. The distribution of the rays in this hemisphere is symmetric about the local z axis and is defined by a cubic spline fit to arbitrary intensity vs. angle data. The number of points can be any integer between 5 and 181, inclusive. The angular range is evenly divided among the specified number of points. The data for each point is the relative intensity measured in the far field of the source at the angle corresponding to that point. The provided data is fit to a cubic spline. Rays generated from the spline fit will follow the correct distribution in the far field of the source.
However, note that the spline fit can be a poor representation of the source in regions where the intensity is varying sharply if enough input data points are not supplied to describe the variation in these regions. A common example is near the angular boundaries of the source (i.e. at the Minimum and Maximum Angle values) if the relative intensity at either of those boundaries is a large fraction of the maximum intensity for the source; since the intensity just outside of the boundaries is zero, this leads to a large discontinuity in the source intensity at the boundaries that the spline fit will not be able to adequately represent.
The parameters are:
| Parameter # | Definition |
| 1-5 | See " Parameters common to all source objects " . |
| 6 | X Half Width: The x half width in lens units. If less than zero, the emitting region will be elliptical. |
| 7 | Y Half Width: The y half width in lens units. If less than zero, the emitting region will be elliptical. |
| 8 | Minimum Angle in degrees. The value must be between 0.0 and 89.9. |
| 9 | Maximum Angle in degrees. The value must be between the minimum angle plus 0.1 and 90.0. |
| 10 | The number of points, must be between 5 and 181, inclusive. |
| 11+ | The relative intensity data at each angle from the normal. |
Use with LightningTrace
The angular distribution of the source is taken for the input data (parameters 8, 9, 10, 11+). The size and spatial distribution of the source is neglected, and thus the X and Y Half Widths (parameters 6, 7) have no effect on the LightningTrace results.
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