Drawing transparent ShapeRenderer in libgdx

Question

I have a drawn a filled circle using ShapeRenderer and now I want to draw this circle as a transparent one. I am using the following code to do that: But the circle is not coming as transparent. Also, I checked th libgdx API and from the wiki, it says that, need to Create CameraStrategy. Has somebody faced similar issue ever before? If so, please give me some clues. Thanks in advance.

 Gdx.gl.glEnable(GL10.GL_BLEND);
      Gdx.gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);
      drawFilledCircle();
      Gdx.gl.glDisable(GL10.GL_BLEND);

private void drawFilledCircle(){

   shapeRenderer.setProjectionMatrix(camera.combined);
   shapeRenderer.begin(ShapeType.FilledCircle);
   shapeRenderer.setColor(new Color(0, 1, 0, 1));
   shapeRenderer.filledCircle(470, 45, 10);
   shapeRenderer.end();

}

If you don't mind me asking, why do you want to draw a transparent circle? — Zach Latta, Feb 05 '13 at 08:12
@crynix, basically I need to understand how can I use ShapeRenderer to display transparancy. I do not want to use a transparent texture here for that. So I wanted to do using ShapeRenederer. — UVM, Feb 05 '13 at 13:10

score 102 · Accepted Answer · edited Dec 31 '15 at 06:08

102

The following code is working for me in this case, maybe it will help someone else:

Gdx.gl.glEnable(GL10.GL_BLEND);
Gdx.gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);
shapeRenderer.setProjectionMatrix(camera.combined);
shapeRenderer.begin(ShapeType.FilledCircle);
shapeRenderer.setColor(new Color(0, 1, 0, 0.5f));
shapeRenderer.filledCircle(470, 45, 10);
shapeRenderer.end();
Gdx.gl.glDisable(GL10.GL_BLEND);

edited Dec 31 '15 at 06:08

Alex Crist

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answered Feb 06 '13 at 04:28

UVM

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Thanks it working but i hope i doesnt mess with other blend stuffs if any – PraveenMax Apr 30 '13 at 15:46
Enabling and disabling blend worked for me also.. however I share @Max_Dev's concern that this might not be the most efficient thing here. – Sean Connolly May 26 '13 at 14:43
14

It is VERY IMPORTANT to stop/pause the current SpriteBatch using mySpriteBatch.end() BEFORE enabling blending! Translucent drawing operations won't work otherwise! :D – Christopher Stock Sep 09 '13 at 08:51
This doesn't need to be before `shapeRenderer.begin()` but it does need to be before `shapeRenderer.setColor()`. – Anubian Noob Oct 26 '15 at 13:43
2

Note: you shouldn't allocate new Color instance on each frame. – Miha_x64 Apr 22 '17 at 17:13
@Miha_x64 you are right. But that was a code snippet only, not the actual code – UVM Apr 24 '17 at 06:25
2

Had to change `GL10` to `GL20` to get it working. Thanks! – Spikatrix Aug 17 '19 at 10:18

score 13 · Answer 2 · answered Mar 06 '14 at 02:44

13

First we need to enable blending:

Gdx.gl.glEnable(GL10.GL_BLEND);

And make sure that you don't call SpriteBatch.begin() and SpriteBatch.end() between that line of code and your Shaperender.drawSomething() line of code. I don't know why but that's what works in my case

answered Mar 06 '14 at 02:44

Hải Phong

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Replace `GL10` with `GL20` for newer versions of LibGDX. – Morgoth Aug 07 '18 at 08:13
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Replace `GL20` with `GL30` for newer versions of LibGDX. – EntangledLoops Jun 12 '20 at 04:22
`GL30` extends `GL20` and `GL30.GL_BLEND` is a static reference to `GL20.GL_BLEND`. – dan1st Jun 20 '21 at 09:49

score 6 · Answer 3 · answered Nov 21 '14 at 09:49

6

Only this worked for me :

Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT | GL20.GL_DEPTH_BUFFER_BIT);
//Gdx.gl.glEnable(GL20.GL_BLEND);
Gdx.gl.glBlendFunc(GL20.GL_SRC_ALPHA, GL20.GL_ONE_MINUS_SRC_ALPHA);   // <<< this line here makes the magic we're after
game.shapeRenderer.setProjectionMatrix(camera.combined);
game.shapeRenderer.begin(ShapeType.Filled);
    go.drawShapes();
game.shapeRenderer.end();
//Gdx.gl.glDisable(GL20.GL_BLEND);

answered Nov 21 '14 at 09:49

Li3ro

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Same thing happened with me. LibGDX discontinued support of OpenGL version 1.x sometime last year. This is likely just the result of using a newer version. – Robert Krupp Jun 11 '15 at 18:14

jellyfication · Answer 4 · 2013-02-05T09:58:21.680

5

Well, there is not really a point in drawing something fully transparent. If you did want to make a half transparent circle, you would have to clear the color buffer by glClearColor before each frame and set Color alpha component to 0.5f.

If you wouldn't clear the buffer, after few render draws, the circle would blend into one with almost solid color.

private void drawFilledCircle(Camera camera){
    Gdx.gl.glClearColor(0, 0, 0, 0); 
    Gdx.gl.glClear( GL10.GL_COLOR_BUFFER_BIT  );

    shapeRenderer.setProjectionMatrix(camera.combined);
    shapeRenderer.begin(ShapeType.FilledCircle);
    shapeRenderer.setColor(new Color(0, 1, 0, 0.5f)); // last argument is alpha channel
    shapeRenderer.filledCircle(470, 45, 10);
    shapeRenderer.end();
}

edited Feb 05 '13 at 09:58

answered Feb 05 '13 at 09:01

jellyfication

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,In my case with the above change, I cannot see the transparancy – UVM Feb 06 '13 at 04:25
For some reason alpha in color works in debug mode (drawing borders of scene2ui elements). But without debug mode I got solid non-transparent colors (same result when alpha is 1f). I'm clearing buffer before every frame. – monnef Feb 17 '15 at 14:55

Drawing transparent ShapeRenderer in libgdx

4 Answers4