Libgdx 将 Bitmap 字体渲染到像素图纹理导致渲染极慢

Question

I'm using libgdx scene2d to render 2d actors. Some of these actors originally included scene2d Label actors for rendering static text. The Labels work fine but drawing ~20 of them on the screen at once drops the frame rate by 10-15 frames, resulting in noticeably poor rendering while dragging.

I'm attempting to avoid the Labels by pre-drawing the text to textures, and rendering the textures as scene2d Image actors. I'm creating the texture using the code below:

    BitmapFont font =  manager.get(baseNameFont,BitmapFont.class);
    GlyphLayout gl = new GlyphLayout(font,"Test Text");

    int textWidth = (int)gl.width;
    int textHeight = (int)gl.height;
    LOGGER.info("textHeight: {}",textHeight);
    //int width = Gdx.graphics.getWidth();
    int width = textWidth;
    //int height = 500;
    int height = textHeight;

    SpriteBatch spriteBatch = new SpriteBatch();

    FrameBuffer m_fbo = new FrameBuffer(Pixmap.Format.RGB565, width,height, false);
    m_fbo.begin();
    Gdx.gl.glClearColor(1f,1f,1f,0f);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
    Matrix4 normalProjection = new Matrix4()

            .setToOrtho2D(0, 0, width,  height);
    spriteBatch.setProjectionMatrix(normalProjection);

    spriteBatch.begin();

    font.draw(spriteBatch,gl,0,height);


    spriteBatch.end();//finish write to buffer

    Pixmap pm = ScreenUtils.getFrameBufferPixmap(0, 0, (int) width, (int) height);//write frame buffer to Pixmap

    m_fbo.end();

    m_fbo.dispose();
    m_fbo = null;
    spriteBatch.dispose();

    Texture texture = new Texture(pm);
    textTexture = new TextureRegion(texture);
    textTexture.flip(false,true);
    manager.add(texture);

I assumed, and have read, that textures are often faster. However when I replaced the Labels with the texture, it had the same, if not worse, affect on the frame rate. Oddly, I'm not experiencing this when adding textures from a file, which makes me think I'm doing something wrong in my code. Is there a different way I should be pre-rendering these pieces of text?

Answer 1

I have not tested this, but I think you can enable culling for the whole Stage by setting its root view to use a cullingArea matching the world width and height of the viewport. I would do this in resize after updating the Stage Viewport just in case the update affects the world width and height of the viewport.

@Override
public void resize(int width, int height) {
    //...
    stage.getViewport().update(width, height, true);
    stage.getRoot().setCullingArea(
        new Rectangle(0f, 0f, stage.getViewport().getWorldWidth(), stage.getViewport().getWorldHeight())
    );
}

It will only be able to cull Actors that have their x, y, width, and height set properly. This is true I think of anything in the scene2d UI package, but for your own custom Actors you will need to do it yourself.

If a child of your root view is a Group that encompasses more than the screen and many actors, you might want to cull its children, too, such that even if the group as a whole is not culled by the root view, the group can still cull a portion of its own children. To figure out the culling rectangle for this, I think you would intersect a rectangle of the group's size with the viewport's world size rectangle offset by -x and -y of the group's position (since the culling rectangle is relative to the position of the group it's set on).