How interactive floor projection works: a truly simple and easy-to-understand explanation

You’ve probably seen those interactive floors in shopping malls or amusement parks where you can “play” with them: when you step on them, ripples form on the water and fish swim away; or you can kick a virtual soccer ball with your feet.

These effects look incredibly magical, making you wonder: How is this even possible? How does the system know my exact location and movements so precisely?Actually, the principle behind it is quite straightforward. The entire system consists of three core components installed on the ceiling, which work together at extremely high speeds to create the interactive effects we see.

Part One: Unveiling the Equipment: Three Core Components

Inside an inconspicuous box mounted on the ceiling lies everything needed to achieve the interactive effects.

1.Projector

This is the easiest component to understand. Its function is to project a clear, bright image onto the ground. All the game visuals we see, such as the reservoir, football field, and piano keys, are projected by this device. To ensure the image remains visible in well-lit environments, ground projectors are typically of a high grade.

2. Sensor

This is the core of the entire system and the key to achieving “interaction.” Its primary function is to monitor all movements occurring on the ground in real time.

Its operating principle can be understood as an extremely advanced “motion sensor.”

• First, it emits an invisible “light grid” (typically infrared) that uniformly covers the entire projection area.
• When no one is walking, this “light grid” remains flat and unchanged.  
• When your foot touches the ground, it disrupts this “light grid,” much like throwing a stone into calm water. The sensor's function is to immediately capture the location, shape, and timing of this “disruption” with extremely high precision.  

3. Computer

The computer serves as the “brain” and “command center” of the entire system. It is connected to the projector and sensors via data cables and is responsible for processing all information and making decisions.  

• It receives real-time motion capture data from the sensors (e.g., “an object shaped like a footprint has appeared at a specific point”).
• It immediately calculates what changes should occur in the image based on pre-set game program rules (e.g., “Rule: If an object steps on point A, generate a water vortex effect at that point”).
• Finally, it sends the generated new image instructions to the projector for execution.

Part Two: Unveiling the Process: Understanding the Interaction Process in Three Steps

Now that we understand the three core components, let's take a look at how they work together to complete an interaction. The entire process can be simplified into three major steps:

Step 1: Sensors “detect” the action

When you enter the interactive area and your feet touch the ground, you have interrupted the invisible “light grid.” The sensors immediately “detect” this action and capture the precise location of your feet in the form of digital signals for control.

Step 2: The computer “decides” what to do

The sensors transmit the captured position signals to the computer at lightning speed. Upon receiving the signals, the computer immediately matches them with the game program.

For example, if the current game is soccer, the computer's program rules state: “If a kicking motion is detected at this position, calculate the trajectory of the soccer ball after it is kicked.” The computer completes this calculation in a fraction of a second.

Step 3: The projector “draws” the response

After the computer completes the calculation, it immediately sends the new image—an animation of the soccer ball flying out—to the projector. The projector receives the instruction and projects this new image onto the ground every second without fail.

Final effect:
From your perspective, when you kick the virtual soccer ball with your foot, the ball lifts up and is “kicked” into the air.

Key point: Speed determines “magic”

The entire process of “seeing the action → deciding on a response → drawing the image” consists of three steps, but it happens at a speed that is beyond imagination.

This entire process can occur in a loop 30 to 60 times within the participant.

Because it happens so quickly, our brains cannot perceive any delay in the intermediate speed. Therefore, we experience an immediate, fleeting, and seemingly real interactive effect. This is the truth behind the “magic.”

Why is this interactive effect so appealing?

1. The satisfaction of instant feedback: When human behavior elicits a response from the environment, the “cause-and-effect relationship” brings immense satisfaction.
2. The novelty of surprise: It challenges our preconceived notion that “the ground is calm,” offering the same sense of surprise.
3. Zero-barrier participation: No learning is required; participation can be achieved through the most natural physical movements, allowing both the elderly and young children to easily engage together and enjoy the fun.  

Now, you should have a complete understanding of how interactive floor projection works.

It's not mysterious. Simply put, sensors on the ceiling “detect” your movements, a computer ‘decides’ what should happen, and a projector “draws” the response on the floor. All of this happens at extremely high speeds, creating a noticeable interactive experience.