Question

I’m looking to draw a cube at specific co-ordinates. I’ve got all 4 corners and the centers x/y value. I now want to construct a cube at those co-ordinates. Does anyone know of any tutorials or have any information on how I would go about said task?

Ive got the following code. I’d like to map each of its corners to a specific x/y co-ord

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.IntBuffer;
import javax.microedition.khronos.opengles.GL10;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.opengl.GLUtils;

 class GLCube {
    private final IntBuffer mVertexBuffer;


  private final IntBuffer mTextureBuffer;


   public GLCube() {

  int one = 65536;
  int half = one / 2;
  int vertices[] = {
        // FRONT
        -half, -half, half, half, -half, half,
        -half, half, half, half, half, half,
        // BACK
        -half, -half, -half, -half, half, -half,
        half, -half, -half, half, half, -half,
        // LEFT
        -half, -half, half, -half, half, half,
        -half, -half, -half, -half, half, -half,
        // RIGHT
        half, -half, -half, half, half, -half,
        half, -half, half, half, half, half,
        // TOP
        -half, half, half, half, half, half,
        -half, half, -half, half, half, -half,
        // BOTTOM
        -half, -half, half, -half, -half, -half,
        half, -half, half, half, -half, -half, };



  int texCoords[] = {
        // FRONT
        0, one, one, one, 0, 0, one, 0,
        // BACK
        one, one, one, 0, 0, one, 0, 0,
        // LEFT
        one, one, one, 0, 0, one, 0, 0,
        // RIGHT
        one, one, one, 0, 0, one, 0, 0,
        // TOP
        one, 0, 0, 0, one, one, 0, one,
        // BOTTOM
        0, 0, 0, one, one, 0, one, one, };



  // Buffers to be passed to gl*Pointer() functions must be
  // direct, i.e., they must be placed on the native heap
  // where the garbage collector cannot move them.
  //
  // Buffers with multi-byte data types (e.g., short, int,
  // float) must have their byte order set to native order
  ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length * 4);
  vbb.order(ByteOrder.nativeOrder());
  mVertexBuffer = vbb.asIntBuffer();
  mVertexBuffer.put(vertices);
  mVertexBuffer.position(0);



  // ...
  ByteBuffer tbb = ByteBuffer.allocateDirect(texCoords.length * 4);
  tbb.order(ByteOrder.nativeOrder());
  mTextureBuffer = tbb.asIntBuffer();
  mTextureBuffer.put(texCoords);
  mTextureBuffer.position(0);

 }


 public void draw(GL10 gl) {
  gl.glVertexPointer(3, GL10.GL_FIXED, 0, mVertexBuffer);


  gl.glEnable(GL10.GL_TEXTURE_2D); // workaround bug 3623
  gl.glTexCoordPointer(2, GL10.GL_FIXED, 0, mTextureBuffer);



  gl.glColor4f(1, 1, 1, 1);
  gl.glNormal3f(0, 0, 1);
  gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 4);
  gl.glNormal3f(0, 0, -1);
  gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 4, 4);

  gl.glColor4f(1, 1, 1, 1);
  gl.glNormal3f(-1, 0, 0);
  gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 8, 4);
  gl.glNormal3f(1, 0, 0);
  gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 12, 4);

  gl.glColor4f(1, 1, 1, 1);
  gl.glNormal3f(0, 1, 0);
  gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 16, 4);
  gl.glNormal3f(0, -1, 0);
  gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 20, 4);
 }


  static void loadTexture(GL10 gl, Context context, int resource) {
  Bitmap bmp = BitmapFactory.decodeResource(
        context.getResources(), resource);
  GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bmp, 0);
  gl.glTexParameterx(GL10.GL_TEXTURE_2D,
        GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_LINEAR);
  gl.glTexParameterx(GL10.GL_TEXTURE_2D,
        GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR);
  bmp.recycle();
 }

}

Answer 1

if you just want to translate your cube to x y coordinate use

gl.glTranslatef(x, y, 0);

before drawing it.

this is a tutorial for opengl transformations in android.