3D graphics for Java mobile devices, Part 1: M3G's immediate mode

/*
 * Sample code for M3G article on IBM developerWorks.
 * http://www.ibm.com/developerworks/
 */

package m3gsamples1;

import java.util.*;
import javax.microedition.lcdui.*;
import javax.microedition.m3g.*;

/**
 * Sample displaying a lit cube with material properties.
 *
 * @author Claus Hoefele
 */
public class TexturesSample extends Canvas implements Sample
{
  /** The cube"s vertex positions (x, y, z). */
  private static final byte[] VERTEX_POSITIONS = {
    -1, -1,  1,    1, -1,  1,   -1,  1,  1,    1,  1,  1, // front
     1, -1, -1,   -1, -1, -1,    1,  1, -1,   -1,  1, -1, // back
     1, -1,  1,    1, -1, -1,    1,  1,  1,    1,  1, -1, // right
    -1, -1, -1,   -1, -1,  1,   -1,  1, -1,   -1,  1,  1, // left
    -1,  1,  1,    1,  1,  1,   -1,  1, -1,    1,  1, -1, // top
    -1, -1, -1,    1, -1, -1,   -1, -1,  1,    1, -1,  1  // bottom
  };

  /** Indices that define how to connect the vertices to build 
   * triangles. */
  private static final int[] TRIANGLE_INDICES = {
     0,  1,  2,  3,   // front
     4,  5,  6,  7,   // back
     8,  9, 10, 11,   // right
    12, 13, 14, 15,   // left
    16, 17, 18, 19,   // top
    20, 21, 22, 23,   // bottom
  };

  /** Lengths of triangle strips in TRIANGLE_INDICES. */
  private static int[] TRIANGLE_LENGTHS = {
    4, 4, 4, 4, 4, 4
  };

  /** File name of the texture. */
  private static final String TEXTURE_FILE = "/texture.png";

  /** The texture coordinates (s, t) that define how to map the 
   * texture to the cube. */
  private static final byte[] VERTEX_TEXTURE_COORDINATES = {
    0, 1,   1, 1,   0, 0,   1, 0,   // front
    0, 1,   1, 1,   0, 0,   1, 0,   // back
    0, 1,   1, 1,   0, 0,   1, 0,   // right
    0, 1,   1, 1,   0, 0,   1, 0,   // left
    0, 1,   1, 1,   0, 0,   1, 0,   // top
    0, 1,   1, 1,   0, 0,   1, 0,   // bottom
  };

  /** First color for blending. */
  private static final int COLOR_0 = 0x000000FF;

  /** Second color for blending. */
  private static final int COLOR_1 = 0x0000FF00;

  /** The cube"s vertex data. */
  private VertexBuffer _cubeVertexData;

  /** The cube"s triangles defined as triangle strips. */
  private TriangleStripArray _cubeTriangles;

  /** The cube"s transformation. */
  private Transform _cubeTransform;

  /** Our cube"s appearance. */
  private Appearance _cubeAppearance;

  /** Polygon mode component of appearance that encapsulates per-face
   * attributes. */
  private PolygonMode _polygonMode;

  /** Stores whether perspective correction is enabled or not. */
  private boolean _isPerspectiveCorrectionEnabled;

  /** The cube"s texture. */
  private Texture2D _cubeTexture;

  /** Graphics singleton used for rendering. */
  private Graphics3D _graphics3d;

  /**
   * Called when this sample is displayed.
   */
  public void showNotify()
  {
    init();
  }

  /**
   * Initializes the sample.
   */
  protected void init()
  {
    // Get the singleton for 3D rendering.
    _graphics3d = Graphics3D.getInstance();

    // Create vertex data.
    _cubeVertexData = new VertexBuffer();

    VertexArray vertexPositions =
        new VertexArray(VERTEX_POSITIONS.length/3, 3, 1);
    vertexPositions.set(0, VERTEX_POSITIONS.length/3, VERTEX_POSITIONS);
    _cubeVertexData.setPositions(vertexPositions, 1.0f, null);

    VertexArray vertexTextureCoordinates =
        new VertexArray(VERTEX_TEXTURE_COORDINATES.length/2, 2, 1);
    vertexTextureCoordinates.set(0,
        VERTEX_TEXTURE_COORDINATES.length/2, VERTEX_TEXTURE_COORDINATES);
    _cubeVertexData.setTexCoords(0, vertexTextureCoordinates, 2.0f, null);

    // Set default color for cube.
    _cubeVertexData.setDefaultColor(COLOR_0);

    // Create the triangles that define the cube; the indices point to
    // vertices in VERTEX_POSITIONS.
    _cubeTriangles = new TriangleStripArray(TRIANGLE_INDICES,
        TRIANGLE_LENGTHS);

    // Create a camera with perspective projection.
    Camera camera = new Camera();
    float aspect = (float) getWidth() / (float) getHeight();
    camera.setPerspective(30.0f, aspect, 1.0f, 1000.0f);
    Transform cameraTransform = new Transform();
    cameraTransform.postTranslate(0.0f, 0.0f, 10.0f);
    _graphics3d.setCamera(camera, cameraTransform);

    // Rotate the cube so we can see three sides.
    _cubeTransform = new Transform();
    _cubeTransform.postRotate(20.0f, 1.0f, 0.0f, 0.0f);
    _cubeTransform.postRotate(45.0f, 0.0f, 1.0f, 0.0f);

    // Define an appearance object and set the polygon mode.
    _cubeAppearance = new Appearance();
    _polygonMode = new PolygonMode();
    _isPerspectiveCorrectionEnabled = false;
    _cubeAppearance.setPolygonMode(_polygonMode);

    try
    {
      // Load image for texture and assign it to the appearance. The
      // default values are: WRAP_REPEAT, FILTER_BASE_LEVEL/
      // FILTER_NEAREST, and FUNC_MODULATE.
      Image2D image2D = (Image2D) Loader.load(TEXTURE_FILE)[0];
      _cubeTexture = new Texture2D(image2D);
      _cubeTexture.setBlending(Texture2D.FUNC_DECAL);

      // Index 0 is used because we have only one texture.
      _cubeAppearance.setTexture(0, _cubeTexture);
    }
    catch (Exception e)
    {
      System.out.println("Error loading image " + TEXTURE_FILE);
      e.printStackTrace();
    }
  }

  /**
   * Renders the sample on the screen.
   *
   * @param graphics the graphics object to draw on.
   */
  protected void paint(Graphics graphics)
  {
    _graphics3d.bindTarget(graphics);
    _graphics3d.clear(null);
    _graphics3d.render(_cubeVertexData, _cubeTriangles,
        _cubeAppearance, _cubeTransform);
    _graphics3d.releaseTarget();

    drawMenu(graphics);
  }

  /**
   * Draws a menu on the screen.
   *
   * @param graphics graphics context.
   */
  protected void drawMenu(Graphics graphics)
  {
    graphics.setColor(0xFFFFFFFF);
    int fontHeight = graphics.getFont().getHeight();

    // Upper half menu.
    int height = 0;
    graphics.drawString(getKeyName(getKeyCode(FIRE)) + ": Reset", 0, height, 0);
    height += fontHeight;
    graphics.drawString(
        getKeyName(getKeyCode(LEFT)) + "/" +
        getKeyName(getKeyCode(RIGHT)) + ": Rotate y ", 0, height, 0);

    // Lower half menu.
    height = getHeight() - fontHeight;
    if (_cubeVertexData.getDefaultColor() == COLOR_0)
    {
      graphics.drawString(getKeyName(getKeyCode(GAME_C)) +
          ": Color: blue", 0, height, 0);
    }
    else
    {
      graphics.drawString(getKeyName(getKeyCode(GAME_C)) +
          ": Color: green", 0, height, 0);
    }

    height -= fontHeight;
    if (_cubeTexture.getWrappingS() == Texture2D.WRAP_CLAMP)
    {
      graphics.drawString(getKeyName(getKeyCode(GAME_B)) +
          ": Wrapping: clamp", 0, height, 0);
    }
    else
    {
      graphics.drawString(getKeyName(getKeyCode(GAME_B)) +
          ": Wrapping: repeat", 0, height, 0);
    }

    height -= fontHeight;
    if (isPerspectiveCorrectionSupported())
    {
      if (_isPerspectiveCorrectionEnabled)
      {
        graphics.drawString(getKeyName(getKeyCode(GAME_A)) +
            ": Persp. correction: on", 0, height, 0);
      }
      else
      {
        graphics.drawString(getKeyName(getKeyCode(GAME_A)) +
            ": Persp. correction: off", 0, height, 0);
      }
    }
    else
    {
      graphics.drawString(getKeyName(getKeyCode(GAME_A)) +
          ": Persp. correction: not supported", 0, height, 0);
    }
  }

  /**
   * Checks whether perspective correction is supported.
   *
   * @return true if persepctive correction is supported, false otherwise.
   */
  protected boolean isPerspectiveCorrectionSupported()
  {
    Hashtable properties = Graphics3D.getProperties();
    Boolean supportPerspectiveCorrection =
        (Boolean) properties.get("supportPerspectiveCorrection");

    return supportPerspectiveCorrection.booleanValue();
  }

  /**
   * Handles key presses.
   *
   * @param keyCode key code.
   */
  protected void keyPressed(int keyCode)
  {
    switch (getGameAction(keyCode))
    {
      case LEFT:
        _cubeTransform.postRotate(-10.0f, 0.0f, 1.0f, 0.0f);
        break;

      case RIGHT:
        _cubeTransform.postRotate(10.0f, 0.0f, 1.0f, 0.0f);
        break;

      case FIRE:
        init();
        break;

      case GAME_A:
        if (isPerspectiveCorrectionSupported())
        {
          _isPerspectiveCorrectionEnabled = !_isPerspectiveCorrectionEnabled;
          _polygonMode.setPerspectiveCorrectionEnable(
              _isPerspectiveCorrectionEnabled);
        }
        break;

      case GAME_B:
        if (_cubeTexture.getWrappingS() == Texture2D.WRAP_CLAMP)
        {
          _cubeTexture.setWrapping(Texture2D.WRAP_REPEAT,
              Texture2D.WRAP_REPEAT);
        }
        else
        {
          _cubeTexture.setWrapping(Texture2D.WRAP_CLAMP,
              Texture2D.WRAP_CLAMP);
        }
        break;

      case GAME_C:
        if (_cubeVertexData.getDefaultColor() == COLOR_0)
        {
          _cubeVertexData.setDefaultColor(COLOR_1);
        }
        else
        {
          _cubeVertexData.setDefaultColor(COLOR_0);
        }
        break;

      // no default
    }

    repaint();
  }

  /**
   * Handles key repeat events for phones that support them. Redirects
   * all key input to <code>keyPressed()</code>.
   *
   * @param keyCode key code.
   */
  protected void keyRepeated(int keyCode)
  {
    keyPressed(keyCode);
  }

  /**
   * Returns the <code>Displayable</code> used to display this sample.
   *
   * @return display
   */
  public Displayable getDisplayable()
  {
    return this;
  }

  /**
   * Returns the display name of this sample.
   *
   * @return name
   */
  public String getName()
  {
    return "Textures";
  }
}