My latest "NDI doodle" is a 4-way colour-gradient pattern generator which transmits the image via NDI.
It uses selectable colours for each of the four corners of the rectangle, although pairs can be set to the same value in order to achieve a simple 2-way gradient. The gradient image can either remain static or the colours can rotate in a clockwise (CW) or anticlockwise (CCW) direction. A slider control adjusts the period between colour changes (i.e. faster rotational speed as the slider moves to the right).
The gradient image can either fill the screen, be horizontally (H-Split) or vertically mirrored (V-Split) as two half-size rectangles, or be mirrored both horizontally and vertically (in Quad mode) using quarter-size rectangles. The Cloud overlay option adds a fixed fractal noise pattern, self-keyed over the background.
The current version (v188.8.131.52) is available to download from my zenvideo website (NOTE: There is a "watermark" logo which appears on the NDI output, but it disappears after several minutes of usage.)