Square and angular shapes. They have more key points than round objects. Round shapes are smooth without sharp transitions, so the image will be difficult to identify.
► Example of a bad shape:
Here we can see the shape without sharp lines. Such an image will be hard to detect.
► Even though a square has 4 corners, which are easy to detect... such a shape is not used for one reason — the square is symmetric, so it becomes impossible to determine its orientation in space. If you turn the square by 90º, nothing changes. That’s why it’s better not to use this figure as a marker.
►An example of a perfect shape is a triangle.