Package breitband.GUI.util

Class PolygonOptimizer

java.lang.Object

breitband.GUI.util.PolygonOptimizer

public class PolygonOptimizer
extends java.lang.Object

Class for optimizing the polygons used in the GUI. All methods are static. They take a Polygon and return a (usually simplified) GPolygon

Only high quality Polygons are optimized, low quality polygons (less than 20 points) get rerouted to generateHQPolygon(Border)

Basic simplification steps:

1. Skip every second point to remove jaggies (exception: neighbouring points are too far apart).
2. Use frequency analysis to simplify the model. In this case frequency is the speed of change/the angle of change, in the model's outline. E.g a corner is high frequency and a straight line or slight curve is low frequency.
   • First detect edges/'high frequency' points using convolution with an edge detection kernel (-1, 2, -1), this kernel is based on edge detection kernels used in shaders. The result is low frequency points being close to [0,0] and high frequency points being far from 0,0. The distance to the origin is saved as the frequency. This low-frequency information is subsequently deleted by skipping the low-frequency points.
   • Leftover points are "blurred" with a weighted blur kernel. In this case a blur leads to the curves getting smoothed, leading to more appealing "simplified" looking shapes.
3. As a last step, the points are iterated over and the distances are accumulated. Only when the distance is greater than a set threshold, does a point get added. This way, levels of detail can be created based on different distance threshold.

Author:

Juno Veenstra

See Also:

generateSimplifiedPolygon(Border, LevelOfDetail)

Constructor Summary

Constructors

Constructor	Description
PolygonOptimizer()

Method Summary

Modifier and Type	Method	Description
static float[]	calculateCenter(Border polygon, float stepSize)	Walks over every point at a constant distance, adds them together and calculates
static sag.elements.shapes.GPolygon	generateHQPolygon(Border polygon)	Generate a full quality GPolygon, these most likely run rather slow
static sag.elements.shapes.GPolygon	generateSimplifiedPolygon(Border polygon, LevelOfDetail lod)	Generate a simplified GPolygon, these should make the renderer run faster.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PolygonOptimizer

public PolygonOptimizer()

Method Detail

generateSimplifiedPolygon

public static sag.elements.shapes.GPolygon generateSimplifiedPolygon(Border polygon,
                                                                     LevelOfDetail lod)

Generate a simplified GPolygon, these should make the renderer run faster.

The LOD sets the allowed distance between points. A higher distance means more points getting left out. When zoomed out, high levels can get used, when zooming in lower levels can get used

Parameters:

polygon - A PolygonWithIntersects from a Region

lod - The degree to which the polygon gets simplified. Higher lod leads to more simplification

Returns:

simplified GPolygon

See Also:

PolygonOptimizer

generateHQPolygon

public static sag.elements.shapes.GPolygon generateHQPolygon(Border polygon)

Generate a full quality GPolygon, these most likely run rather slow

Parameters:

polygon - a PolygonWithIntersects from a Region

Returns:

full quality GPolygon

calculateCenter

public static float[] calculateCenter(Border polygon,
                                      float stepSize)

Walks over every point at a constant distance, adds them together and calculates

Parameters:

polygon - Polygon of which the center needs to be found

stepSize - Distance between sampled points

Returns:

A float array of length 2, with the x coordinate at index 0 and the y coordinate at index y