How can I clip a circle?

Question

How can I clip a circle using libGDX? Clipping a rectangle very easy Gdx.gl.glScissor(int x,int y,int width,int height). Is there any method to clip a circle or do I need some algorithm?

While searching for "libgdx clip circle" doesn't yield much help, perhaps searching for a general opengl solution might help you find something that you can use. Try googling "opengl clip circle", for example. — tobloef, Sep 19 '15 at 16:58
That command works for anything you draw??? so give me an example using circle?? the command takes position and **width** and **height** as parameters what about circle **radius**?? — mobarmig, Sep 19 '15 at 20:46
Are you saying you want to cut a slice of the pie, as it were, for the circle clipping? — Malkierian, Sep 20 '15 at 05:56
Your question sounded to me like you were asking how to clip a circle, not how to clip an arbitrary shape *with* a circle. The clip command always clips a rectangle out of whatever you draw after it. For anything other than a rectangle, you cannot simply clip. You need to use multi-texturing with a custom shader program. But the way to do it depends on exactly what you are doing. Are you cutting the same circle out of many sprites or just one? — Tenfour04, Sep 20 '15 at 14:27
And are you clipping multiple different circles from different areas on the screen. — Tenfour04, Sep 20 '15 at 14:32
I am drawing multiple objects using **PolygonSpriteBatch** and **SpriteBatch** and **ShapeRenderer** and I would like to draw objects (lines , images, fill shapes) inside a circle , you said I need **multi-texturing with a custom shader program** can you explain more or give some example or link to docs. — mobarmig, Sep 21 '15 at 11:13
OK I found some examples and docs for shader program and there is another way to do clipping with depth buffer , I am just search for easiest it solution to do circle clipping?? — mobarmig, Sep 21 '15 at 11:47
http://stackoverflow.com/questions/37716128/modify-picture-resource-to-rounded-rectangle-border-in-libgdx — Jing Hu, Jul 07 '16 at 09:54

mobarmig · Answer 1 · 2015-09-22T18:51:25.827

It is possible to clip circle by using depth buffer :

    //clear screen

    Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);

    //clear depth buffer with 1.0 : 

    Gdx.gl.glClear(GL10.GL_DEPTH_BUFFER_BIT);

    //set the function to LESS

    Gdx.gl.glDepthFunc(GL20.GL_LESS);

    //enable depth writing

    Gdx.gl.glEnable(GL20.GL_DEPTH_TEST);

    //Enable depth mask and disable RGBA color writing

    Gdx.gl.glDepthMask(true);

   Gdx.gl.glColorMask(false, false, false, false);

    //rendering(Circle ect..) primitive shapes

    shapeRenderer.begin();
    shapeRenderer.circle(x, y, radius);
    shapeRenderer.end();

    batch.begin();

     //Enable RGBA color writing

    Gdx.gl.glColorMask(true, true, true, true);

    //Enable testing

    Gdx.gl.glEnable(GL10.GL_DEPTH_TEST);

    //Discards pixels outside masked shapes

    Gdx.gl.glDepthFunc(GL10.GL_EQUAL);

    batch.draw(...);

    batch.end();

How can I clip a circle?

1 Answers1