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   1 /*
   2  * Sixth 3D engine. Author: Svjatoslav Agejenko.
   3  * This project is released under Creative Commons Zero (CC0) license.
   4  */
   5 package eu.svjatoslav.sixth.e3d.renderer.raster.shapes.composite.solid;
   6
   7 import eu.svjatoslav.sixth.e3d.geometry.Point3D;
   8 import eu.svjatoslav.sixth.e3d.renderer.raster.Color;
   9 import eu.svjatoslav.sixth.e3d.renderer.raster.shapes.basic.solidpolygon.SolidPolygon;
  10 import eu.svjatoslav.sixth.e3d.renderer.raster.shapes.composite.base.AbstractCompositeShape;
  11
  12 /**
  13  * A solid cylinder oriented along the Y-axis.
  14  *
  15  * <p>The cylinder has circular top and bottom caps connected by a curved side
  16  * surface made of rectangular panels. The number of segments determines the
  17  * smoothness of the curved surface.</p>
  18  *
  19  * <p><b>Usage example:</b></p>
  20  * <pre>{@code
  21  * // Create a cylinder with radius 50, height 100, and 16 segments
  22  * SolidPolygonCylinder cylinder = new SolidPolygonCylinder(
  23  *     new Point3D(0, 0, 200), 50, 100, 16, Color.RED);
  24  * shapeCollection.addShape(cylinder);
  25  * }</pre>
  26  *
  27  * @see SolidPolygonCube
  28  * @see SolidPolygonSphere
  29  * @see SolidPolygon
  30  */
  31 public class SolidPolygonCylinder extends AbstractCompositeShape {
  32
  33     /**
  34      * Constructs a solid cylinder centered at the given point.
  35      *
  36      * @param center   the center point of the cylinder in 3D space.
  37      *                 The cylinder is centered on the Y-axis, extending
  38      *                 {@code height/2} above and below this point.
  39      * @param radius   the radius of the cylinder
  40      * @param height   the total height of the cylinder
  41      * @param segments the number of segments around the circumference.
  42      *                 Higher values create smoother cylinders. Minimum is 3.
  43      * @param color    the fill color applied to all polygons
  44      */
  45     public SolidPolygonCylinder(final Point3D center, final double radius,
  46                                 final double height, final int segments,
  47                                 final Color color) {
  48         super();
  49
  50         final double halfHeight = height / 2.0;
  51         final double bottomY = center.y - halfHeight;
  52         final double topY = center.y + halfHeight;
  53
  54         Point3D bottomCenter = new Point3D(center.x, bottomY, center.z);
  55         Point3D topCenter = new Point3D(center.x, topY, center.z);
  56
  57         Point3D[] bottomRing = new Point3D[segments];
  58         Point3D[] topRing = new Point3D[segments];
  59
  60         for (int i = 0; i < segments; i++) {
  61             double angle = 2.0 * Math.PI * i / segments;
  62             double x = center.x + radius * Math.cos(angle);
  63             double z = center.z + radius * Math.sin(angle);
  64             bottomRing[i] = new Point3D(x, bottomY, z);
  65             topRing[i] = new Point3D(x, topY, z);
  66         }
  67
  68         for (int i = 0; i < segments; i++) {
  69             int next = (i + 1) % segments;
  70
  71             addShape(new SolidPolygon(
  72                     new Point3D(bottomCenter.x, bottomCenter.y, bottomCenter.z),
  73                     new Point3D(bottomRing[i].x, bottomRing[i].y, bottomRing[i].z),
  74                     new Point3D(bottomRing[next].x, bottomRing[next].y, bottomRing[next].z),
  75                     color));
  76
  77             addShape(new SolidPolygon(
  78                     new Point3D(topCenter.x, topCenter.y, topCenter.z),
  79                     new Point3D(topRing[next].x, topRing[next].y, topRing[next].z),
  80                     new Point3D(topRing[i].x, topRing[i].y, topRing[i].z),
  81                     color));
  82
  83             addShape(new SolidPolygon(
  84                     new Point3D(bottomRing[i].x, bottomRing[i].y, bottomRing[i].z),
  85                     new Point3D(topRing[i].x, topRing[i].y, topRing[i].z),
  86                     new Point3D(bottomRing[next].x, bottomRing[next].y, bottomRing[next].z),
  87                     color));
  88
  89             addShape(new SolidPolygon(
  90                     new Point3D(bottomRing[next].x, bottomRing[next].y, bottomRing[next].z),
  91                     new Point3D(topRing[i].x, topRing[i].y, topRing[i].z),
  92                     new Point3D(topRing[next].x, topRing[next].y, topRing[next].z),
  93                     color));
  94         }
  95
  96         setBackfaceCulling(true);
  97     }
  98 }