OpenGL ES Tutorial for Android – Part V – More on Meshes

Per-Erik Bergman

I have a feeling that some of you have tried my tutorials and then thought "This is a 3D tutorial, but why is everything in 2D?". So in this tutorial we will make some real 3D meshes. This is also necessary for the following tutorials.

When I started I had problems with finding out how to programmatic make different meshes like cubes, cones and so on. I needed this so I easy easy could put my scenes together. So this tutorial will show how to make some of the basic primitives. They might not be the most effective way of creating them but it is a way of doing them.

Starting point will be from the source of the second tutorial. I will show you plane and cube and then give you a couple of hint for additional primitives.

Design

A good place to start when designing an OpenGL framework is to use the composite pattern. This is a start of how I would proceed:

Let's start making out pattern.

Mesh

It's a good idea to have a common base for your meshes. So let us start by creating a class called Mesh.

package se.jayway.opengl.tutorial.mesh;
public class Mesh {
 
}

We add the draw function from previous example, since I when over this function in a previous tutorial I just show it here:

    // Our vertex buffer.
    private FloatBuffer verticesBuffer = null;
 
    // Our index buffer.
    private ShortBuffer indicesBuffer = null;
 
    // The number of indices.
    private int numOfIndices = -1;
 
    // Flat Color
    private float[] rgba = new float[]{1.0f, 1.0f, 1.0f, 1.0f};
 
    // Smooth Colors
    private FloatBuffer colorBuffer = null;
 
    public void draw(GL10 gl) {
        // Counter-clockwise winding.
	gl.glFrontFace(GL10.GL_CCW);
	// Enable face culling.
	gl.glEnable(GL10.GL_CULL_FACE);
	// What faces to remove with the face culling.
	gl.glCullFace(GL10.GL_BACK);
	// Enabled the vertices buffer for writing and to be used during
	// rendering.
	gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
	// Specifies the location and data format of an array of vertex
	// coordinates to use when rendering.
	gl.glVertexPointer(3, GL10.GL_FLOAT, 0, verticesBuffer);
        // Set flat color
        gl.glColor4f(rgba[0], rgba[1], rgba[2], rgba[3]);
        // Smooth color
        if ( colorBuffer != null ) {
            // Enable the color array buffer to be used during rendering.
            gl.glEnableClientState(GL10.GL_COLOR_ARRAY);
            // Point out the where the color buffer is.
            gl.glColorPointer(4, GL10.GL_FLOAT, 0, colorBuffer);
        }
	gl.glDrawElements(GL10.GL_TRIANGLES, numOfIndices,
		GL10.GL_UNSIGNED_SHORT, indicesBuffer);
	// Disable the vertices buffer.
	gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
	// Disable face culling.
	gl.glDisable(GL10.GL_CULL_FACE);
    }

We need functions where the subclasses can set the vertices and the indices. These function contains nothing new and are pretty much the same as you seen in earlier tutorials.

    protected void setVertices(float[] vertices) {
	// a float is 4 bytes, therefore we multiply the number if
	// vertices with 4.
	ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length * 4);
	vbb.order(ByteOrder.nativeOrder());
	verticesBuffer = vbb.asFloatBuffer();
	verticesBuffer.put(vertices);
	verticesBuffer.position(0);
    }
 
    protected void setIndices(short[] indices) {
	// short is 2 bytes, therefore we multiply the number if
	// vertices with 2.
	ByteBuffer ibb = ByteBuffer.allocateDirect(indices.length * 2);
	ibb.order(ByteOrder.nativeOrder());
	indicesBuffer = ibb.asShortBuffer();
	indicesBuffer.put(indices);
	indicesBuffer.position(0);
	numOfIndices = indices.length;
    }
 
    protected void setColor(float red, float green, float blue, float alpha) {
        // Setting the flat color.
        rgba[0] = red;
        rgba[1] = green;
        rgba[2] = blue;
        rgba[3] = alpha;
    }
 
    protected void setColors(float[] colors) {
	// float has 4 bytes.
	ByteBuffer cbb = ByteBuffer.allocateDirect(colors.length * 4);
	cbb.order(ByteOrder.nativeOrder());
	colorBuffer = cbb.asFloatBuffer();
	colorBuffer.put(colors);
	colorBuffer.position(0);
    }

We need to add a couple of things. When we start working with multiple meshes we need to be able to move and rotate them individual so let us add translation and rotation parameters:

    // Translate params.
    public float x = 0;
    public float y = 0;
    public float z = 0;
 
    // Rotate params.
    public float rx = 0;
    public float ry = 0;
    public float rz = 0;

And use them in the draw function add this lines just before the gl.glDrawElements call.

    gl.glTranslatef(x, y, z);
    gl.glRotatef(rx, 1, 0, 0);
    gl.glRotatef(ry, 0, 1, 0);
    gl.glRotatef(rz, 0, 0, 1);

Plane

Let us start making a plane an quite easy task you might think and it kinda is. But to make it more interesting and more useful we need to be able to create it with some different settings like: width, depth, how many width segments and how many depth segments.

Just so we have the same terminology, width is the length over the x-axis, depth is over the z-axis and height is over the y-axis. Look at the image below as a visual input.

Width, height and depth.

Width, height and depth.

Segments is how many parts the length should be divided by. This is useful if you need to make a surface that is not total even. If you create a plane over x, y and make z not all be 0 say you give z a random span from -0.1 to 0.1 you will get something you could use as a ground plane in a game just put a nice texture on it.

Segments.

Segments.

Looking at the image above you see that the different segments gives you squares. Since we like it to be triangles so just split them up into 2 triangles.

I hate frameworks and classes that don't have a default setup and easy class constructors I try to always have more then one constructor. The constructors I will put in this plane is:

For an easy and quick setup:

// Gives you a plane that is 1 unit wide and 1 unit high with just one segment over width and height.
public Plane()

An easy one just to change the size:

 // Let you decide the size of the plane but still only one segment.
public Plane(float width, float height)

And finally one for setting up the plane with different segments:

// For alla your settings.
public Plane(float width, float height, int widthSegments, int heightSegments)

If I in theory would construct a plane that is 1 unit wide and 1 units high with 4 segments in both width and height direction it would look like this images:

The one to the left shows the segments and the one to the right show us the faces we need to create.

package se.jayway.opengl.tutorial.mesh;
 
public class Plane extends Mesh {
 
    public Plane() {
	this(1, 1, 1, 1);
    }
 
    public Plane(float width, float height) {
	this(width, height, 1, 1);
    }
 
    public Plane(float width, float height, int widthSegments,
		int heightSegments) {
	float[] vertices = new float[(widthSegments + 1) * (heightSegments + 1)
			* 3];
	short[] indices = new short[(widthSegments + 1) * (heightSegments + 1)
			* 6];
 
	float xOffset = width / -2;
	float yOffset = height / -2;
	float xWidth = width / (widthSegments);
	float yHeight = height / (heightSegments);
	int currentVertex = 0;
	int currentIndex = 0;
	short w = (short) (widthSegments + 1);
	for (int y = 0; y < heightSegments + 1; y++) {
            for (int x = 0; x < widthSegments + 1; x++) {
	        vertices[currentVertex] = xOffset + x * xWidth;
		vertices[currentVertex + 1] = yOffset + y * yHeight;
		vertices[currentVertex + 2] = 0;
		currentVertex += 3;
 
		int n = y * (widthSegments + 1) + x;
 
		if (y < heightSegments && x < widthSegments) {
		    // Face one
		    indices[currentIndex] = (short) n;
		    indices[currentIndex + 1] = (short) (n + 1);
		    indices[currentIndex + 2] = (short) (n + w);
		    // Face two
		    indices[currentIndex + 3] = (short) (n + 1);
		    indices[currentIndex + 4] = (short) (n + 1 + w);
		    indices[currentIndex + 5] = (short) (n + 1 + w - 1);
 
		    currentIndex += 6;
		}
	    }
	}
 
	setIndices(indices);
	setVertices(vertices);
    }
}

Cube

The next step I think a cube will be nice. I will only make a cube that you can set: height, width and depth on but I suggest you as a practice make it with segments just as we did with the plane.

The constructor will look like this:

public Cube(float width, float height, float depth)

And since I'm not doing this with any segments the constructor will be quite easy.

package se.jayway.opengl.tutorial.mesh;
 
public class Cube extends Mesh {
    public Cube(float width, float height, float depth) {
        width  /= 2;
        height /= 2;
        depth  /= 2;
 
        float vertices[] = { -width, -height, -depth, // 0
                              width, -height, -depth, // 1
                              width,  height, -depth, // 2
                             -width,  height, -depth, // 3
                             -width, -height,  depth, // 4
                              width, -height,  depth, // 5
                              width,  height,  depth, // 6
                             -width,  height,  depth, // 7
        };
 
        short indices[] = { 0, 4, 5,
                            0, 5, 1,
                            1, 5, 6,
                            1, 6, 2,
                            2, 6, 7,
                            2, 7, 3,
                            3, 7, 4,
                            3, 4, 0,
                            4, 7, 6,
                            4, 6, 5,
                            3, 0, 1,
                            3, 1, 2, };
 
        setIndices(indices);
        setVertices(vertices);
    }
}

If you like to make it with segments the constructor could look like this:

public Cube(float width, float height, float depth,
                 int widthSegments, int heightSegments, int depthSegments)

Since we now have a plane that replaces the Square class ( in the code from tutorial II ) I will just remove it and in OpenGLRenderer change the square to a cube...

public OpenGLRenderer() {
    // Initialize our cube.
    cube = new Cube(1, 1, 1);
    cube.rx = 45;
    cube.ry = 45;
}

... and render it.

public void onDrawFrame(GL10 gl) {
    ...
    // Draw our cube.
    cube.draw(gl);
}

Group

A group is really good to have when setting up and controlling your 3D scene. What a group really do is to distribute all commands sent to the group to all it's children. You can see the implementation of a simple group here:

package se.jayway.opengl.tutorial.mesh;
 
import java.util.Vector;
 
import javax.microedition.khronos.opengles.GL10;
 
public class Group extends Mesh {
    private Vector<Mesh> children = new Vector<Mesh>();
 
    @Override
    public void draw(GL10 gl) {
        int size = children.size();
        for( int i = 0; i < size; i++)
            children.get(i).draw(gl);
    }
 
    public void add(int location, Mesh object) {
        children.add(location, object);
    }
 
    public boolean add(Mesh object) {
        return children.add(object);
    }
 
    public void clear() {
        children.clear();
    }
 
    public Mesh get(int location) {
        return children.get(location);
    }
 
    public Mesh remove(int location) {
        return children.remove(location);
    }
 
    public boolean remove(Object object) {
        return children.remove(object);
    }
 
    public int size() {
        return children.size();
    }
}

Make the renderer work with a group as a root node and add your cube to it.

Group group = new Group();
Cube cube = new Cube(1, 1, 1);
cube.rx = 45;
cube.ry = 45;
group.add(cube);
root = group;

And draw our scene:

public void onDrawFrame(GL10 gl) {
    ...
    // Draw our scene.
    root.draw(gl);
}

Suggestions

It's always a good idea to have different primitives ready to use when you starting up a new project. My experience tell me that in 9 times of 10 you won't have any meshes from the graphic people when you start coding so it's really good to have some meshes to work with as place holders. I'll give you a hint of the way to start with your own meshes library by giving you an idea of how I would do it.

Creating your own meshes is a really good way of getting to know vertices and indices really close up.

Cone

After you have gotten your cube up and ready to go my suggestion is that you move onto a cone. A cone with the right settings could be more then just a cone. if you give is 3-4 sides it will be a pyramid. If you give it the same base and top radius it becomes a cylinder. So you can see why it is so useful. Take a look at this image and see what the this cone can do.

public Cone(float baseRadius, float topRadius, float height, int numberOfSides)

Pyramid

public class Pyramid extends Cone {
    public Pyramid(float baseRadius, float height)  {
        super(baseRadius, 0, height, 4);
    }
}

Cylinder

public class Cylinder extends Cone {
    public Cylinder(float radius, float height)  {
        super(radius, radius, height, 16);
    }
}

One more thing

Dividing up surfaces is a good thing to know about and by now you know how to divide up a regular square. To divide up a triangle look at the images below. It is a bit different and it might be a bit harder to implement.

References

The info used in this tutorial is collected from:
Android Developers
OpenGL ES 1.1 Reference Pages

You can download the source for this tutorial here: Tutorial_Part_V
You can also checkout the code from: code.google.com

Previous tutorial: OpenGL ES Tutorial for Android – Part IV – Adding colors
Next tutorial: OpenGL ES Tutorial for Android – Part VI – Textures

Per-Erik Bergman
Consultant at Jayway

Tags: , ,

71 comments ↓

#1 Jason Odom on 02.22.10 at 5:15

Another Great tutorial.. keep them coming

#2 Andy on 02.24.10 at 23:04

Great series! Would love to see a tutorial on loading textures. Keep up the good work!

#3 Per-Erik Bergman on 02.25.10 at 9:02

Next tutorial will be about textures so stay tuned :)

#4 Kernle 32DLL on 02.26.10 at 16:40

Excellent tutorial. I only read this tutorial so far, to verify i did all correctly myself. I wish i had this tutorial when i started :)

#5 mtf on 03.01.10 at 17:31

Fantastic tutorial! Congratulations! I am impacient waiting the next one! When will it be?

#6 Spobo on 03.06.10 at 18:31

you are realy doing a great job :) when will you post the next tutorial?

#7 Vaughan on 03.09.10 at 21:38

Really helpful thanks. Any chance of doing a surface normals / lighting tutorial for the next one?

#8 Imti on 03.16.10 at 3:03

cant wait to get home and try these out

#9 vinpa on 03.18.10 at 15:45

Another nice tutorial.

Could you possibly explain the math involved here? I am pretty sure I grasped the equations you used to determine vertices and indices, but a brief explanation would be greatly appreciated! : )

Thanks!

#10 Omega on 03.21.10 at 23:49

As always, complete and 100% applicable. Great tutorials!

I’d love to see a tutorial from you on ray picking on Android!

#11 Winchester on 03.28.10 at 21:29

Thank you for your tutorial!

But i got a curious..about Cylinder.
Because i’d like to make a Cylinder.

If you gotta some time..
Could U make a Cylinder part plz~!

I’m so sorry about question.

#12 Ankita on 04.06.10 at 8:03

Thanks for such a great tutorial!

Eagerly waiting for the next part on textures!! :)
Thanks again!

#13 Per-Erik Bergman on 04.06.10 at 13:55

vinpa: I’m not sure what math you need, I try to draw every thing on paper and then recreate it in java.
Omega: Ray picking will be done, but not now. My plan is to do all the basics first.
Winchester: I don’t have the time at the moment to write about a cylinder. Basicly you do it just as you would do a plane but with with sin/cos to gain the circle shape.

And as always I’m happy that you read and like my posts.

#14 canny on 04.08.10 at 12:22

please continue with tutorials . Really they are very much help full. thank u thank u…….. please go ahead dont stop.

#15 Quicols Consultancy Services on 04.14.10 at 3:20

Hi,
First of all really great tutorials.
I have been trying your suggestion on creating the cone.I could draw tetrahedron with the little geometry but could not imagine the generic equation to decide the vertices.At present I am thinking of

//for a Cone like figure if number of sides 3 then verices = 4
//For a Cylinder like figure if number of sides = 3 then vertices = 6
int noOfVertices = numberOfSides + ((topRadius == 0) ? 1 : numberOfSides);

for most of the cases it may work but for winding the final figure I could not reach to generic LOOP kind of logic. Could you please suggest.

Thanking you in advance.
Keep up the great work.

Regards,
Quicols Consultancy Services

#16 Checkus on 04.17.10 at 10:13

Hi,

Excellent tutorial. I have just one problem :
When I made more then one cube in one group and when I draw the cube i have a problem with the translation.

// Code //
for (int i = 0; i < 3; i++){
Cube enemy = new Cube(1, 1, 1);
enemy.x = i + 0.0f;
EnemyG.add(i, enemy);
}
// END CODE //

As you can see the third cube are too shifted. I have the impression that it takes for reference the last cube.

Is it normal?

Thanks!

(Sorry for my English, I’m french)

#17 NoviceAndroidDev on 04.19.10 at 22:05

Hello, I just would like to know how would one go about making it so the cube rotates only upon a key press on the android. For example, let’s say I want to make the cube rotate to the left only when the left key is pressed down. How would this be done? I can’t seem to figure out a way to implement a listener with the OpenGLRenderer class.

#18 AndroidOpenGLBeginner on 04.26.10 at 20:35

@NoviceAndroidDev you can check out lesson 7 here http://insanitydesign.com/wp/projects/nehe-android-ports/

Implements Event Listeners for key presses. It should be fairly easy to do.

#19 Ramana on 05.19.10 at 10:11

First of all Excellent tutorials.
Iam doing an augment reality application on android.I have camera preview on surface view.Now i would like to have a 3d grid on GLSurfaceview which rotates with sensor values and i should be able to overlay some png images on to grid which moves accordingly.How do i acheive this?

#20 Daniel Rodríguez on 05.21.10 at 18:54

Awesome tutorial. Thank you very much.

Texturing would be great, can’t wait. I would also like to see a tutorial on importing OBJs.

Congratulations for this great series.

#21 Musa on 05.22.10 at 19:07

Just followed this tutorial but could u please explain the math involved? It would be highly/greatly appreciated if u do.. Thanks and keep up the good work!

#22 lost on 05.31.10 at 19:05

Is it possible to have the correction of this tutorial: the cube with segment, please ?

#23 Nov on 06.04.10 at 18:17

These tutorials are really really good, and are a life saver for people new to not only openGL ES but openGL in general.

Please keep on writing more tutorials for the betterment of the public!

#24 David on 06.16.10 at 22:32

Thanks for a very good starting tutorial to OpenGL Es, wish there was something like this on the android site.

#25 Alex on 06.20.10 at 21:47

The cube mesh example has the vertices backwards, so you actually have to set the winding to clock-wise instead of counter-clock wise..unless I’m doing something wrong

#26 Alex on 06.20.10 at 22:30

These are the right indices for counter-clockwise order:

short indices[] = {
0, 1, 5,
0, 5, 4,
1, 0, 3,
1, 3, 2,
1, 2, 6,
1, 6, 5,
5, 6, 7,
5, 7, 4,
4, 7, 3,
4, 3, 0,
6, 2, 3,
6, 3, 7,
};

#27 JON on 06.30.10 at 14:50

Thank you. This is a great tutorial. OpenGL has always intimidated me. I could not find any book on OpenGL ES, specially with Android for beginners. Wish you could publish a book (with the same style of writing). I will definitely buy that one.

#28 Musa on 07.16.10 at 2:02

Don’t mean to be a punk, but when’s the next tutorial coming? The last one came out since Feb.?!

#29 Grass on 07.18.10 at 15:44

Please give us next tutorial :)

#30 John on 07.22.10 at 6:45

First, kudos for putting the tutorials together, I’ve been following them closely.

Quick question – In the draw() method, why is gl.glDisableClientState(GL10.GL_VERTEX_ARRAY) called, but gl.glDisableClientState(GL10.GL_COLOR_ARRAY) is never called?

#31 Per Sandström on 08.24.10 at 16:07

Hi,

awesome tutorial! I’m really looking forward to the texture-tutorial! My current application only succeeds with loading textures that are exactly 256*256 pixles for some reason :(

#32 Fluckysan on 08.25.10 at 12:01

There are very good tutorial :)
Keep in going !

#33 Anh Nguyen on 09.09.10 at 18:49

Hi Bergman,
This tutorial series is great, it helps me a lot in learning OpenGLES.
The explanation is clear and the code runs well :) .
Thanks a lot.

#34 Mustafa on 10.04.10 at 11:27

Thanks alot buddy… Loving your tutorials. Helpful… precise and perfect. Made it so easy for person who has started programming recently.

#35 Vishnu on 10.07.10 at 9:17

Hey,
Awesome tutorials…Best one for beginners..TRUST ME..
Thanks man…..

And uhh…I think it will be a lot more easier if you use GL_TRIANGLE_FAN or GL_TRIANGLE_STRIP to draw circle or square like structures….But be careful while applying colors or textures…

#36 Uma Maheswari on 10.11.10 at 11:31

hey
thanks for the tutorials…
could you please help me with the following thing?
actually m done with loading different images on all the faces.
i need to create a text view or an editable text view on one of the faces of the cube.. M really stuck up with this..Please lend a help..
Thanks

#37 Espen on 10.20.10 at 15:25

Three words: Write-a-book. I would buy it. I have done lots of OpenGL programming in the past and now I just need a jolt of information for OpenGL ES. Hoping for texturing soon though it seems a long time since the last tutorial…

#38 ommar on 10.25.10 at 19:10

Should we be waiting for 6th. tutorial ?

#39 Cisco on 11.20.10 at 2:47

Is the 6th tutorial coming out?

#40 sreekanth on 11.23.10 at 12:29

really awesome material , please give me an idea regarding drawing arc shape which is badly needed for my project

#41 sreekanth on 11.23.10 at 12:35

please suggest me if there are any tool that convert the “openg gl” code to “opengl es”.Actually i got a code to draw arc in c language but i am unable to convert that code into java(android) .
really great explanation,
i am eagerly waiting for your next tutorial
thanks in advance

#42 PaulC on 11.25.10 at 23:34

I have been reading every site I can find trying to get a proper primer on opengl. For me everything starts at too high a level. Your explanations, examples, diagrams and code examples are everything I have been searching for.

I can imagine that such good stuff takes a very long time to produce, but please don’t give up, as I for one will vouch for the almost unique usefulness of this series of tutorials.

As others have said, if you wrote a book along these lines I would buy it.

Waiting with antisipation for the next tutorial.

Thank you very much.

#43 Jeffrey Blattman on 11.26.10 at 20:29

awesome tutorial.

i was trying to make a cube with distinctly colored sides. i tried translating 8 colored squares into the right places. this works, but i wonder if it’s the right approach?

anyway, if i enable face culling with this approach i get strange results. some sides are hidden when they should not be. i wonder if this is because face culling only works within a given “shape”, and since i have 8 different shapes …

the other problem is that i see the parts of the back faces drawing through to the front, around the edges of the squares. seems to happen at particular angles only.

#44 Riki on 12.01.10 at 17:32

Hello, just wanted to confirm that these tutorial-series is still going or have you (jayway) discontinued it?

#45 RealTime - Questions: "Vector java help please?" on 12.01.10 at 20:05

[...] [...]

#46 Priyanka on 12.15.10 at 6:26

Thanks for tutorial………….
really awesome

#47 sujit panda on 12.27.10 at 7:26

great tutorial…thnaks ………

#48 OpenGL ES Tutorial for Android – Part VI – Textures — Jayway Team Blog on 12.30.10 at 18:46

[...] Previous tutorial: OpenGL ES Tutorial for Android – Part V – More on Meshes [...]

#49 ray on 01.10.11 at 10:01

i just want to add texture to this code but i can’t got it
this is my code

float vertices[] = { -width, -height, -depth, // 0
width, -height, -depth, // 1
width, height, -depth, // 2
-width, height, -depth, // 3
-width, -height, depth, // 4
width, -height, depth, // 5
width, height, depth, // 6
-width, height, depth, // 7
};

short indices[] = {
//FRONT
4, 5, 6,
4, 6, 7,
//BACK
1, 0, 3,
1, 3, 2,
//LEFT
0, 4, 7,
0, 7, 3,
//RIGHT
5, 1, 2,
5, 2, 6,
//TOP
7, 6, 2,
7, 2, 3,
//BOTTOM
0, 1, 5,
0, 5, 4,
};

and textureindex is

float textureCoordinates[] = {
1.0f, 1.0f,
1.0f, 0.0f,
0.0f, 1.0f,
0.0f, 0.0f,

1.0f, 1.0f,
1.0f, 0.0f,
0.0f, 1.0f,
0.0f, 0.0f,

1.0f, 1.0f,
1.0f, 0.0f,
0.0f, 1.0f,
0.0f, 0.0f,

1.0f, 1.0f,
1.0f, 0.0f,
0.0f, 1.0f,
0.0f, 0.0f,

1.0f, 1.0f,
1.0f, 0.0f,
0.0f, 1.0f,
0.0f, 0.0f,

1.0f, 1.0f,
1.0f, 0.0f,
0.0f, 1.0f,
0.0f, 0.0f,
};

what’s wrong with me?
thanks

#50 Andranik on 01.17.11 at 10:28

Hi Per-Erik!

You’re doing a great job in this blog! Simple, clear and professionally!
I have a one little question…

In the Plane constructor you create indices in the clockwise order, but render it in counterclockwise as in previous tutorials. I try it and it works only in this combination, if I replace CCW to CW in draw method (gl.glFrontFace(GL10.GL_CCW) -> gl.glFrontFace(GL10.GL_CW)) I’ll get an empty screen.

Сould you shed some light on this situation?

Best Regards, Andranik

#51 Andranik on 01.18.11 at 7:03

Sorry,

I forget to flip Y-coordinate, the order of the indices is correct.

#52 Alberto on 01.29.11 at 6:14

This is better than any book and tutorial I could find out there. I want to thank for you making this great set of intuitive tutorials, every other piece out there just rewrites the openGL ES technical documents again .

#53 Ricardo Paiva on 02.07.11 at 3:29

Hi,
If you want to draw two planes, when you set plane’s X and Y coordinates, what happens it’s a translation.
What if I want to reset (LoadIdentity) before drawing a new plane, how can I do it?

Thanks in advance!

#54 Shakthi on 02.09.11 at 9:24

Hi Per-Erik,
Thanks a lot for such an excellent Tutorial. I have started programming on OpenGL.

Can you Please tell me how to Draw a Sphere/Circle instead of a Plane?

Waiting for your Reply.

#55 Renan on 02.11.11 at 20:30

Excellent tutorials! Thanks for sharing your knowledge!

I have one question: what is the idea behind this equation (line code):
int n = y * (widthSegments + 1) + x;
?
Thanks again! These tutorials have helped me a lot with my new project!

#56 逍遥十四少 on 03.11.11 at 14:52

太棒了,看了你的教程我才知道原来我们中国的那些教程有的是把你的教程翻译过去的,我晕,我还佩服他们呢,原来鼻祖在这啊,小弟佩服……

#57 逍遥十四少 on 03.11.11 at 15:01

suprised!

it’s 22:00 in my country now,but*****

#58 lattimore on 04.14.11 at 10:28

Excellent!
Great Tutorial!

#59 Rancs on 04.25.11 at 6:42

I have a question about the triangle creation of this tutorial. Here is the indice array given above:
short indices[] = { 0, 4, 5,
0, 5, 1,
1, 5, 6,
1, 6, 2,
2, 6, 7,
2, 7, 3,
3, 7, 4,
3, 4, 0,
4, 7, 6,
4, 6, 5,
3, 0, 1,
3, 1, 2, };

Do the first 2 lines of this array create 2 triangles (0-4-5 and 0-5-1) or 3 triangles? (0-4-5, 4-5-0 and 0-5-1)

#60 Anay Tamhankar on 05.03.11 at 10:50

Hello Per-Erik,

Great set of Tutorials ! Thanks for such excellent resource.

I was looking at the code for memory allocation of indices array in class Plane:

short[] indices = new short[(widthSegments + 1) * (heightSegments + 1)
* 6];

I think the array is getting over-allocated. The correct allocation should be:

short indices[] = new short[(widthSegments) * (heightSegments) * 2
* 3];

My logic:

1) It takes 3 values to represent triangle (last multiplication by 3)
2) The number of triangles in any plane will be (widthSegments * heightSegments * 2).

For example: if a plane is divided into 3 widthsegments and 2 heightsegments, then number of triangles will be 12 (3 * 2 * 2)

Please correct if I am wrong.

Thanks!
Anay

#61 Lance Zimmerman on 05.11.11 at 22:56

Thank you so much, now I can make my sprite engine! I’m going to port my games to Android! You have been of a great help! I must say, this is the only useful tutorial I’ve found. This is what the Android community needs, more people like you!
Sharing knowledge makes us all stronger!

#62 Sam on 05.18.11 at 20:48

Please tell me if there is any way to draw 3D curves… Please reply asap.

Thanks A Lot

#63 CP Gangstaz on 05.25.11 at 10:15

This tutorial is so dope! I’m telling all my homies about it.

#64 abeeleakey on 06.10.11 at 4:11

很不错啊,里面还穿插有设计模式。厉害!

#65 faraon on 08.03.11 at 15:17

Great tutorial! Unfortunatelly there is no GLUT lib for opengl es. Could you please to write about loading and using 3D models. It should be easier then making e.g. sphere from triangles. Thanks.

#66 sensei on 08.14.11 at 7:04

this tutorial is really great,
can you tell me how to load bitmap for cube or other 3D object?
thanks for your help…

#67 nebyan on 09.07.11 at 11:35

this tuorial is really helpful for me
wait for next tutorial.

Thanks a lot …

#68 3D model modeling, mapping, animation Research (Done by Lai Chin Wang) « Maternal App on 09.21.11 at 20:32

[...] http://blog.jayway.com/2010/02/15/opengl-es-tutorial-for-android-%E2%80%93-part-v/ [...]

#69 Julia on 11.18.11 at 6:10

Excellent tutorial! It is really helpful for me, as a java beginner. I want to use java to write a java barcode generator, which I saw from “http://www.onbarcode.com/tutorial/java-barcode-generation.html ”. It is easy-use, I want to write one like it.

#70 Alex on 12.30.11 at 3:13

Hi, great work!

Can you tell me if is possible to use text on OpenGL? Page curl and selectable text?

To resolve this question:
http://stackoverflow.com/questions/8675360/page-curl-with-text-on-android

Thanks

#71 OpenGL ES Tutorial for Android – Part V – More on Meshes | Per-Erik Bergman on 02.01.12 at 18:55

[...] (function() { var s = document.createElement('SCRIPT'), s1 = document.getElementsByTagName('SCRIPT')[0]; s.type = 'text/javascript'; s.async = true; s.src = 'http://widgets.digg.com/buttons.js'; s1.parentNode.insertBefore(s, s1); })(); TweetThis tutorial is original posted at Jayway’s Developer Blog and can be found here: Jayway’s Developer Blog [...]

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