Normals.java

private static Texture generateNormalMapTexture(int width, int height, Pixmap pm) {
        pixmap = new Pixmap(width, height, Pixmap.Format.RGBA8888);
        texture = new Texture(width, height, Pixmap.Format.RGBA8888);

        for (int x = 0; x < width; x++) {
            for (int y = 0; y < height; y++) {
                Vector3 currentVertex = new Vector3(x, getPixelWrap(x, y, width, height, pm), y);
                Vector3 pU = new Vector3(x + 1, getPixelWrap(x + 1, y, width, height, pm), y);
                Vector3 pV = new Vector3(x, getPixelWrap(x, y + 1, width, height, pm), y + 1);

                Vector3 dpU = negate(currentVertex.cpy().sub(pU));
                Vector3 dpV = currentVertex.cpy().sub(pV);

                Vector3 normal = dpU.cpy().crs(dpV).nor();

                Vector3 normalRGB = normal.cpy().scl(0.5f).add(0.5f);

                pixmap.drawPixel(x, y, new Color(normalRGB.x, normalRGB.y, normalRGB.z, 1).toIntBits());
            }
        }


        PixmapIO.writePNG(Gdx.files.getFileHandle("normalmap.png", Files.FileType.Local), pixmap);
        texture.setWrap(Texture.TextureWrap.ClampToEdge, Texture.TextureWrap.ClampToEdge);
        texture.draw(pixmap, 0, 0);
        return texture;
    }

private static final float getPixelWrap(int x, int y, int width, int height, Pixmap pixmap) {
        if(MathUtils.isPowerOfTwo(width) && MathUtils.isPowerOfTwo(height)) {
            if (x < 0 || x >= width) x = (width + x) & (width - 1);
            if (y < 0 || y >= height) y = (height + y) & (height - 1);
            return pixmap.getPixel(x,y);
        } else {
            if (x < 0 || x >= width || y < 0 || y >= height) {
                return pixmap.getPixel((y + height) % height,(x + width) % width);
            } else {
                return pixmap.getPixel(y,x);
            }
        }
    }