[FIXED] Same background color for PC and Android

[Ats]

If we do not set App.ClearColor on the project, screen is black on PC, but white on Android.
If we set a color to something else (ex: RED), it is red on both.
Then, if we set it to BLACK again, it's black on both.

So I suspect that the base background color isn't black, but full transparent.
I suggest that App.ClearColor is set to Black instead of transparent for new projects,
or we could modify the ZgeActivity.java so that the Activity color isn't white, but black by adding:

Code: Select all

import android.graphics.Color;
...
setContentView( zge );
getWindow().getDecorView().setBackgroundColor(Color.BLACK);

NB:
This doesn't solve the transparency problem on Android.

[VilleK]

Its been a long time since I looked at the ZGE Java code. Maybe the recommended way to initialize an OpenGL application is completely different now compared to when this code was written.

When I try searching for "Android transparent OpenGL surface" then the normal problem seems to be that the surface is not transparent by default.

I don't have a Android development environment so it is hard for me to try things. Please do some more investigations. I suspect the problem lies in the Java code somewhere.

[Ats]

After reading that: https://developer.android.com/training/ ... nvironment
I tried adding in zge.java :

Code: Select all

import android.opengl.GLES20;
...
public void onSurfaceCreated( GL10 gl, EGLConfig config )
{
   if(DEBUG) Log.i("ZgeAndroid", "SurfaceCreated: " + gl.glGetString( GL10.GL_VERSION ));

   // Set the background frame color
   GLES20.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);

   NativeSurfaceCreated();
}
...
public void onDrawFrame( GL10 gl )
{
   GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
            
   if(NativeDrawFrame())
      IsDestroy=true;

   if ( IsDestroy )
      Finish();
}

and

<uses-feature android:glEsVersion="0x00020000" android:required="true" />
is already set in the AndroidManifest.xml

But it doesn't solve the Android transparency problem, nor the background color.

[Kjell]

Hi Ats,

If we do not set App.ClearColor on the project, screen is black on PC, but white on Android.
If we set a color to something else (ex: RED), it is red on both. Then, if we set it to BLACK again, it's black on both.

Keep in mind that by default App.ClearColor is {0,0,0,0} ( which matches the default glClearColor state of OpenGL ), but once you select black using the color picker you end up with {0,0,0,1}.

K

[Ats]

That is what I suspected in my first post.
In which case it interesting to start with {0,0,0,0} since the exe can't be transparent?

[Kjell]

Hi Ats,

That is what I suspected in my first post.

If you start a new project and right-click on the color box of App.ClearColor you can see that its alpha value is 0

In which case it interesting to start with {0,0,0,0} since the exe can't be transparent?

You mean a Windows standalone executable? Since Windows Vista there's the option to ( easily ) make the background of a window (semi-)transparent, but it's not enabled by default.

The decision of OpenGL using {0,0,0,0} as default might come from early GLide / OpenGL GPUs being 3D add-on cards instead of standalone cards ( connected to a traditional / 2D GPU using a VGA-to-VGA passthrough cable ), but that's just a wild guess.



K

[Ats]

So the two lines of code in my first post solves the background color on Android, so it is the same as Windows when the ZGE app background color is transparent

The alpha problem on Android is another problem yet to solve. I'm going to make a little PR on github.

[Kjell]

Hi Ats,

Setting the Android activity background to black is probably the easiest OS "solution" yea

By the way, when you enable background transparency in Windows you actually get a semi-transparent result by default ( which is different from Linux ). Not that it matters, but just to indicate that these kind of differences are OS dependent, not OpenGL dependent.



K

[Ats]

Oh nice, I didn't know about that. Last time I saw something like that was with the good old Winamp skins

[Kjell]

Hi Ats,

Oh nice, I didn't know about that.

You can do fully transparent as well of course, which makes the behavior similar to Android / WebGL. Below is what a simple RenderParticles project looks like with the Spotify website in the background ( click image for short video ).

Last time I saw something like that was with the good old Winamp skins

The WinAmp skins used a different technique, but yea .. transparent windows haven't been very popular on PC the last couple of decades

K