Set Libgdx FrameBuffer size in world units

Question

I'had like to use a FrameBuffer and to set his size in world units instead of pixel. When I set the FrameBuffer size in pixel, i have the expected result. But when I use another personal units. The result is messed up.

Here a snippet of the working code:

public class FBOTestLibGDX implements ApplicationListener {

public static void main(String[] args) {
    LwjglApplicationConfiguration cfg = new LwjglApplicationConfiguration();
    cfg.useGL30 = false;
    cfg.width = 640;
    cfg.height = 480;
    cfg.resizable = false;

    new LwjglApplication(new FBOTestLibGDX(), cfg);
}

Texture atlas;
FrameBuffer fbo;
TextureRegion fboRegion;

Matrix4 projection = new Matrix4();
SpriteBatch batch;
OrthographicCamera cam;

@Override
public void create() {
    atlas = new Texture(Gdx.files.local("src/test/resources/fboData/testTexture.jpg"));

    fbo = new FrameBuffer(Format.RGBA8888, atlas.getWidth(), atlas.getHeight(), false);
    fboRegion = new TextureRegion(fbo.getColorBufferTexture(), atlas.getWidth(), atlas.getHeight());
    fboRegion.flip(false, true); // FBO uses lower left, TextureRegion uses
    projection.setToOrtho2D(0, 0, atlas.getWidth(), atlas.getHeight());

    batch = new SpriteBatch();
    batch.setProjectionMatrix(projection);
    cam = new OrthographicCamera(5, 5);
    cam.setToOrtho(false);

    renderTextureInFBO();
}

protected void renderTextureInFBO() {
    fbo.begin();
    Gdx.gl.glClearColor(0f, 0f, 0f, 0f);
    Gdx.gl.glClear(GL30.GL_COLOR_BUFFER_BIT);
    batch.begin();
    batch.setProjectionMatrix(projection);
    batch.draw(atlas, 0, 0);
    batch.end();
    fbo.end();
}

@Override
public void render() {
    Gdx.gl.glClearColor(0, 0, 0, 0f);
    Gdx.gl.glClear(GL30.GL_COLOR_BUFFER_BIT);
    batch.setProjectionMatrix(cam.combined);
    batch.begin();
    batch.draw(fboRegion, 0, 0, 5, 5);
    batch.end();
}

@Override
public void resize(int width, int height) {
    cam.setToOrtho(false, 5, 5);
    //batch.setProjectionMatrix(cam.combined);
}

@Override
public void pause() {}

@Override
public void resume() {}

@Override
public void dispose() {}
}

Using pixel I obtain this result:

But if I use world units for FrameBuffer like this:

public void create() {
    ...
    fbo = new FrameBuffer(Format.RGBA8888, 5, 5, false);
    fboRegion = new TextureRegion(fbo.getColorBufferTexture(), 5, 5);
    fboRegion.flip(false, true);
    projection.setToOrtho2D(0, 0, 5, 5);
    ...
}

protected void renderTextureInFBO() {
    ...
    batch.draw(atlas, 0, 0,5,5);
    ...
}

I obtain a low scaled result:

The question is, it is possible to set the FrameBuffer size in world unit as we do for batch and viewport or it is mandatory to set it in pixel?

I don't know libgdx very well, but defining a framebuffer size in something else than pixels doesn't make much sense. A framebuffer is basically a texture into which you can render. The texture size does not have any relation to world units. — BDL, Aug 30 '18 at 09:04
I do it because I want to draw tiles and to apply effect and blending on them into the framebuffer. So I want to define the framebuffer in world units to make the texture the exact size it would be if a drew the tiles directly in the batch. That way I don't have to deal with pixels and it will be easier to adapt to different screen resolution. — QuentinR, Aug 30 '18 at 09:21
I'm looking for a way to don't have to do it. And to know if the framebuffer specify his size is in pixel. — QuentinR, Aug 30 '18 at 09:51

score 0 · Accepted Answer · answered Sep 02 '18 at 05:50

As specified in the documentation, a FrameBuffer size have to be defined in pixel. cf: FrameBuffer specification

FrameBuffer

public FrameBuffer(Pixmap.Format format, int width, int height, boolean hasDepth, boolean hasStencil)

Creates a new FrameBuffer having the given dimensions and potentially a depth and a stencil buffer attached.

Parameters:

format - the format of the color buffer; according to the OpenGL ES 2.0 spec, only RGB565, RGBA4444 and RGB5_A1 are color-renderable

width - the width of the framebuffer in pixels

height - the height of the framebuffer in pixels

hasDepth - whether to attach a depth buffer

Throws

GdxRuntimeException - in case the FrameBuffer could not be created

Set Libgdx FrameBuffer size in world units

1 Answers1