Comments on: OpenGL ES Tutorial for Android – Part IV – Adding colors

By: vinpa

vinpa — Wed, 17 Mar 2010 15:56:40 +0000

Per-Erik:

Very nice tutorials; I have followed all of them up to this point. I just wanted to say thanks for the nice documentation on the fundamentals of 3D programming using OpenGL. The illustrations are a very nice touch to understanding the whole idea of a matrix.

One thing I found helpful when completing this tutorial was the use of glPushMatrix() and glPopMatrix() to make both squares appear:

@Override public void onDrawFrame(GL10 gl) { // Clear the screen and depth buffer. gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); // Replace current matrix with the identity matrix. gl.glLoadIdentity();


		// FLAT SQUARE

		// Save current matrix.

		gl.glPushMatrix();

		// Translate -10 units into screen, 1.5 units up.

		gl.glTranslatef(0, 1.5f, depth);

		// Draw our flat square.

		flatSquare.draw(gl);

		// ...then restore previous matrix.

		gl.glPopMatrix();
		// SMOOTH SQUARE

		// Save current matrix.

		gl.glPushMatrix();

		// Translate smoothSquare to end up under flatSquare.

		gl.glTranslatef(0, -1.5f, depth);

		// Draw our smooth square.

		smoothSquare.draw(gl);

		// ...then restore previous matrix.

		gl.glPopMatrix();

}

Again, many thanks! I will continue to read through the rest of your posts and look forward to many more! : )

VP.

By: Per-Erik Bergman

Per-Erik Bergman — Thu, 28 Jan 2010 21:36:10 +0000

Yes, I have started on the next tutorial. It will be about more meshes, but 3D meshes so that we get some real 3D objects on the screen.

By: Sam

Sam — Thu, 28 Jan 2010 06:57:26 +0000

All tutorials are really awesome.By now you must have started preparing the next tutorial, can you please tell which topics will be covered in next tutorial.
thanks.

By: arn.zhan

arn.zhan — Tue, 26 Jan 2010 07:49:56 +0000

Mr Bergman , after seeing your tutorials I want to say , this is the best I have ever seen , even better than NeHe’s. If some day you’ve written a book , I will certainly buy one .

By: Al

Al — Sat, 23 Jan 2010 20:12:52 +0000

Excellent tutorials, they have explained a lot of things for me, looking forward to the next one!

By: Per-Erik Bergman

Per-Erik Bergman — Tue, 19 Jan 2010 06:25:04 +0000

Jen: Glad you like my tutorial. About face picking or mesh picking it’s a bit much to share as a comment. But there is two basic ways of doing this;
1. Sending a ray into the screen and calculate which mesh you clicked on,
2. Rendering all meshes with a unique color and when you pick just check for the color. I recommend for beginners since it’s a bit easier.

By: jen

jen — Sun, 17 Jan 2010 15:04:04 +0000

Thank you verry much. This is the best 3d tutorials I’ve found.

There’s something I would like to know. Hope you will help me.

Is there any way to capture touch events on 3D objects drawn in a space?

I just want to select a object or know where I have clicked.

Is it possible?

Thanks.