Make a List<Point3D> , add points and draw using glDrawArrays.

Question

Hey guys,

This is a follow up question from http://stackoverflow.com/questions/3204189/add-contents-to-the-end-of-a-float-array-like-this . I'm looking to dynamically create 3D boxes. Here's my Questions

• I want to add a box to the list e.g add....

  // FRONT
           -2.0f, -1.5f,  -6.0f,
            2.0f, -1.5f,  -6.0f,
           -2.0f,  1.5f,  -6.0f,
            2.0f,  1.5f,  -6.0f,
           // BACK
           -2.0f, -1.5f, -10.0f,
           -2.0f,  1.5f, -10.0f,
            2.0f, -1.5f, -10.0f,
            2.0f,  1.5f, -10.0f,
           // LEFT
           -2.0f, -1.5f,  -6.0f,
           -2.0f,  1.5f,  -6.0f,
           -2.0f, -1.5f, -10.0f,
           -2.0f,  1.5f, -10.0f,
           // RIGHT
            2.0f, -1.5f, -10.0f,
            2.0f,  1.5f, -10.0f,
            2.0f, -1.5f,  -6.0f,
            2.0f,  1.5f,  -6.0f,
           // TOP
           -2.0f,  1.5f,  -6.0f,
            2.0f,  1.5f, -6.0f,
           -2.0f,  1.5f, -6.0f,
            2.0f,  1.5f, -10.0f,
           // BOTTOM
           -2.0f, -1.5f,  -6.0f,
           -2.0f, -1.5f, -10.0f,
            2.0f, -1.5f,  -6.0f,
            2.0f, -1.5f, -10.0f,
  

The above values would make up 1 box, how would I do so?

• I'd like to use glDrawArrays() to then draw the entire list (all of the boxes) how would I make it do so?

          FloatBuffer makeFloatBuffer(float[] arr) {
  ByteBuffer bb = ByteBuffer.allocateDirect(arr.length*4);
  bb.order(ByteOrder.nativeOrder());
  FloatBuffer fb = bb.asFloatBuffer();
  fb.put(arr);
  fb.position(0);
  return fb;
  

  }

keep in mind, I'm sending everything through a floatbuffer. and then drawing like so..

            gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 4);          
    gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 4, 4);
    gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 8, 4);
    gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP,12, 4);
    gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP,16, 4);
    gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP,20, 4);

I'm completely new to Point3D, OpenGL and graphics in general so any help would be greatly appreciated.

Thanks.

Answer 1

Now that you've added the opengl tag I understand why you need float[] structures (or at least floats instead of doubles).

Here is demo application. To me it looks like a good piece of code for studying opengl basics, including the vertex arrays. From other question I see that you work on an android project. So I just hope that it's applicable to android too.