libgdx 裁剪多边形(clip polygon、masking polygon)

public static void drawClip(Batch batch, Polygon polygon, TextureRegion region, float x, float y) {
        float[] vertices = polygon.getVertices();
        if (shapes == null) {
            shapes = new ShapeRenderer();
        }
        //2. clear our depth buffer with 1.0
        Gdx.gl.glClearDepthf(1f);
        Gdx.gl.glClear(GL20.GL_DEPTH_BUFFER_BIT);

        //3. set the function to LESS
        Gdx.gl.glDepthFunc(GL20.GL_LESS);

        //4. enable depth writing
        Gdx.gl.glEnable(GL20.GL_DEPTH_TEST);

        //5. Enable depth writing, disable RGBA color writing
        Gdx.gl.glDepthMask(true);
        Gdx.gl.glColorMask(false, false, false, false);

        ///////////// Draw mask shape(s)

        //6. render your primitive shapes
        shapes.begin(ShapeRenderer.ShapeType.Filled);

        shapes.setColor(1f, 0f, 0f, 0.5f);
        shapes.identity();
        shapes.triangle(vertices[0], vertices[1], vertices[4], vertices[5], vertices[2], vertices[3]);
        shapes.triangle(vertices[0], vertices[1], vertices[4], vertices[5], vertices[6], vertices[7]);
//        shapes.polyline(polygon.getVertices());

        shapes.end();

        ///////////// Draw sprite(s) to be masked
        if (!batch.isDrawing()) {
            batch.begin();
        }

        //8. Enable RGBA color writing
        //   (SpriteBatch.begin() will disable depth mask)
        Gdx.gl.glColorMask(true, true, true, true);

        //9. Make sure testing is enabled.
        Gdx.gl.glEnable(GL20.GL_DEPTH_TEST);

        //10. Now depth discards pixels outside our masked shapes
        Gdx.gl.glDepthFunc(GL20.GL_EQUAL);

        //push to the batch
        batch.draw(region, x, y);
        //end/flush your batch
        batch.end();
        Gdx.gl.glDisable(GL20.GL_DEPTH_TEST);
    }