this is an attempt to port this shader to libgdx https://www.shadertoy.com/view/XdcXDN#

libGdxFromShaderToy.java

package de.qx.shaders.CustomFrameBuffer;

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.Screen;
import com.badlogic.gdx.assets.AssetManager;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.graphics.g2d.TextureRegion;
import de.qx.shaders.ShaderManager;

/**
 * @author Michael "molp" Olp
 */
public class FrameBufferScreen implements Screen {

    private static final String MARBLE = "img/tex02.jpg";
    private static final String BUFFER_A = "img/black.png";

    private AssetManager assetManager;
    private boolean assetsLoaded;

    private final SpriteBatch batch;
    private ShaderManager shaderManager;

    private TextureRegion marble;
    private TextureRegion bufferA;
    private float time = 100f;

    public FrameBufferScreen() {
        assetManager = new AssetManager();
        assetManager.load(MARBLE, Texture.class);
        assetManager.load(BUFFER_A, Texture.class);
        shaderManager = new ShaderManager(assetManager);
        shaderManager.loadShader("bufferA", "default.vert", "bufferA.frag");
        shaderManager.loadShader("dissolve", "default.vert", "dissolve.frag");
        shaderManager.loadShader("default", "default.vert", "default.frag");

        batch = new SpriteBatch();
    }

    @Override
    public void render(float delta) {
        Gdx.gl.glClearColor(0f, 0f, 0f, 1f);
        Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

        if (!assetsLoaded) {
            if (assetManager.update()) {
                assetsLoaded = true;

                build();
            }
        } else {
            shaderManager.beginFrameBuffer("frameBuffer01");
            shaderManager.begin("bufferA");

            batch.enableBlending();
            batch.begin();
            batch.setShader(shaderManager.getCurrentShader());

            shaderManager.setUniformMatrix("u_projTrans", batch.getProjectionMatrix());
            shaderManager.setUniform2fv("iMouse", new float[]{Gdx.input.getX(), Gdx.input.getY()});

            shaderManager.setUniformTexture("u_texture", shaderManager.getFrameBuffer("frameBuffer01").getColorBufferTexture());
            shaderManager.setUniform2fv("iResolution", new float[]{Gdx.graphics.getWidth(), Gdx.graphics.getHeight()});


            batch.draw(bufferA, 0f, 0f);
            batch.end();
            shaderManager.end();
            shaderManager.endFrameBuffer();

            shaderManager.begin("dissolve");


            shaderManager.setUniformMatrix("u_projTrans", batch.getProjectionMatrix());
            shaderManager.setUniform2fv("iResolution", new float[] { Gdx.graphics.getWidth(), Gdx.graphics.getHeight()});
            time+= 0.01;
            shaderManager.setUniformf("iGlobalTime", time);
            shaderManager.setUniformTexture("u_texture", marble.getTexture());
            shaderManager.setUniformTexture("u_texture1", shaderManager.getFrameBuffer("frameBuffer01").getColorBufferTexture());

            shaderManager.renderFrameBuffer("frameBuffer01");
            batch.setShader(shaderManager.getCurrentShader());

            batch.begin();
            batch.draw(marble, 0f, 0f);
            batch.end();
            shaderManager.end();
        }
    }

    private void build() {
        marble = new TextureRegion(assetManager.<Texture>get(MARBLE));
        bufferA = new TextureRegion(assetManager.<Texture>get(BUFFER_A));

        shaderManager.createFrameBuffer("frameBuffer01");
    }

    @Override
    public void resize(int width, int height) {
    }

    @Override
    public void pause() {
    }

    @Override
    public void resume() {
    }

    @Override
    public void show() {
    }

    @Override
    public void hide() {
    }

    @Override
    public void dispose() {
        shaderManager.dispose();

        assetManager.unload(MARBLE);
        assetManager.unload(BUFFER_A);
        assetManager.dispose();
        
    }
}