• Create Account

## Android + GLES 2.0 - Why Can't I See Anything? (SOLVED)

Old topic!

Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.

5 replies to this topic

### #1elliotpotts  Members

130
Like
0Likes
Like

Posted 13 February 2014 - 04:29 PM

Hi everyone - this is my first post on GameDev.net and I apologise that it is just asking for help! I cannot for the life of me get this code to display anything. All I want is a quad on the screen (or anything, then I can work from there!)

Here is the code: https://gist.github.com/elliotpotts/8983783

I don't understand what is wrong - I thought I'd done everything:
• Generated index + vertex buffers
• Put data into the buffers
• Bound the buffers and used the programme
• Set up the vertex layout
• Drawn with glDrawElements
But still all I can see is the orange screen from glClear! I can't find any errors in the log either.

Any help or insight would be much appreciated!
Thanks. Ell.

### #2HScottH  Members

520
Like
0Likes
Like

Posted 13 February 2014 - 04:47 PM

Here are some things to try:

* Use your Projection. You are not calling your method to build the projection matrix, but you are pushing it to the shader.  Yet, you are not using it in the shader (mutiply that vec4(...) with it).

* Turn off culling explicitly.

* Push your geometry a little positive from 0 in the Z direction.

* Change the 2 to a 4 in the glDrawElements call; this number represents the number of indices, not triangles

* Try changing from GL_TRIANGLE_STRIP to GL_TRIANGLES

### #3elliotpotts  Members

130
Like
0Likes
Like

Posted 13 February 2014 - 05:30 PM

Thanks for the tips - I don't gave access to my computer until the morning now (GMT) but as soon as I can I will try those things out and report with the results - if you think of anything in the mean time please post it here and I will check this thread to see if anyone has come up wit anything else. Thanks again

### #4KoMaXX  Members

601
Like
0Likes
Like

Posted 14 February 2014 - 09:31 AM

Hi elliotpotts,

welcome to the special hell that is graphics programming ;)

Since I haven't found anything particularly wrong with your code, try the following:

* Add a GLES20.glGetError() after every single GLES20 function call you do. It it ever returns anything but 0, you've found your problem.

Otherwise, try to dumb it down:

* Do not use a vertex buffer, but push the vertices directly

* Use a simple orthographic projection

* Play with the z-value (negate it, +10, -10, ...). It may be that your geometry simply is not in the viewing area.

* Swear

Hope that helps!

Go on, feed your brain: http://poroba.com/flip/flipz.php

### #5elliotpotts  Members

130
Like
0Likes
Like

Posted 14 February 2014 - 11:38 AM

Okay, so I tried doing GLES20.glGetError() after every GLES20 function call and all of them were 0. I've tried fiddling with the z values - still can't see anything. I've now tried without any matrices at all which should draw the vertices in window coordinates - https://gist.github.com/elliotpotts/9005362

I don't want to try without a vertex & element buffer because this is what I need to achieve! I still have no clue why I'm not seeing anything because the above code is very minimal.

### #6elliotpotts  Members

130
Like
1Likes
Like

Posted 14 February 2014 - 12:12 PM

Ahh I fixed the issue - I was trying to use the GLES20 as if it were a C api therefore I was not using native ByteBuffers! I have to allocate buffers with ByteBuffer.allocateDirect and then fill them with data.

Old topic!

Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.