← IGCSE Computer Science Paper 1

3D scanner

An input device that uses lasers, light patterns or cameras to measure many points on an object's surface and combine them into a digital 3D model of its shape.

Part of: IGCSE Computer Science 0478 — 3.2 Input and Output Devices — Module 16

Understanding 3D scanner in IGCSE Computer Science Paper 1

What it does: Lasers, light patterns or cameras are used to measure how far each point on the surface is from the scanner. A 3D scanner is an input device. It captures a real object. A 3D printer is an output device that makes one. Many distance readings are combined to build the 3D model. One reading would not capture the shape. Scanning from several angles, or turning the object on a turntable, captures every surface for a complete model. Scanned models can be sent to a 3D printer to make copies. A keyboard is used for typing text. Heritage work uses scanning to keep a digital record of objects and to share them without handling them.

Common mistakes: This overwrites the model on every loop, so only the last angle is kept. The readings from all angles must be combined, so it should be APPEND(model, reading). A 3D printer is an output device that makes objects. The device that measures a real object and captures its shape is the 3D scanner.

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This module's key terms are also in a printable crossword (Modules 252–261) and word search (Modules 240–261).

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Learning
Duo
Which statement describes what a 3D scanner does?
It prints a real object from a digital 3D modelIt captures the shape of a real object as a digital 3D model
Matches
A 3D scanner is an output device that prints a copy of an object
↓
A 3D scanner is an input device that captures the shape of an object. Printing a copy is done by a 3D printer, which is an output device.
Applying
Meanings
Term
3D scanner
Meaning
An input device that uses lasers, light patterns or cameras to measure many points on an object's surface and combine them into a digital 3D model of its shape.
Practice
Count ← 0
Testing
Gaps
device ←
Check Answer
Spots
3 reading ← SCAN(angle)
4 model ← reading

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Quick Questions

1. Which statement describes what a 3D scanner does?
A. It captures the shape of a real object as a digital 3D model ✓
B. It prints a real object from a digital 3D model
A 3D scanner is an input device. It captures a real object. A 3D printer is an output device that makes one.
2. How does a 3D scanner build up a model of an object?
A. It takes one reading from the centre of the object
B. It measures the distance to many points on the surface ✓
Many distance readings are combined to build the 3D model. One reading would not capture the shape.
3. Which can a 3D scanner use to measure points on a surface?
A. Lasers, light patterns or cameras ✓
B. Magnets, keys or microphones
3D scanners use lasers, projected light patterns or cameras to measure the surface.
4. Is a 3D scanner an input device or an output device?
A. Output device, because it produces a solid object
B. Input device, because it sends data about an object into the computer ✓
It captures data from the real world and sends it to the computer, so it is an input device.
5. How can a scanner capture all sides of an object?
A. Scan from several angles or rotate the object ✓
B. Scan the front only and let the software guess the rest
Scanning from several angles, or turning the object on a turntable, captures every surface for a complete model.

Match the Pairs

3D scanner → An input device that measures the distance to many points on an object's surface to capture its shape as a digital 3D model
point cloud → The many distance readings from the surface of an object, combined by software to build the 3D model
A scanner uses a laser, light pattern or camera to measure points on the surface of an object → laser.measureDistance(point)
The object is scanned from several angles or rotated on a turntable so the whole shape is captured → for angle in range(0, 360, 45): scan(angle)
A 3D scanner is an output device that prints a copy of an object → A 3D scanner is an input device that captures the shape of an object. Printing a copy is done by a 3D printer, which is an output device.
A 3D scanner takes one reading of an object to build its 3D model → A 3D scanner needs many readings from many points on the surface, often from several angles, to build an accurate 3D model.

Key Term

3D scanner
An input device that uses lasers, light patterns or cameras to measure many points on an object's surface and combine them into a digital 3D model of its shape.

Fill in the Blanks

1. device ← 3D scanner model ← device.SCAN(object) OUTPUT model
Hint: Type the name of the input device that captures an object's shape and surface.
2. points ← MeasureSurface(object) model ← BuildModel(points)
Hint: Type the function name that combines the many surface readings into a digital 3D model.
3. FOR angle ← 0 TO 270 STEP 90 SCAN(object, angle) NEXT angle
Hint: Type the keyword that starts a loop so the object is scanned from several angles.
4. model ← SCAN(object) SEND model TO 3D printer
Hint: Type the output device that can turn the scanned model into a physical copy.
5. IF pointCount > 0 THEN model ← BuildModel(points) ENDIF
Hint: Type the keyword that starts the code to run when some readings have been captured.

Spot the Error

Question 1
A model ← []
B FOR angle ← 0 TO 270 STEP 90
C reading ← SCAN(angle)
D model ← reading
E NEXT angle
Line D — This overwrites the model on every loop, so only the last angle is kept. The readings from all angles must be combined, so it should be APPEND(model, reading).
Question 2
A device ← "3D printer"
B points ← MEASURE(device)
C model ← BUILD(points)
D OUTPUT model
Line A — A 3D printer is an output device that makes objects. The device that measures a real object and captures its shape is the 3D scanner.
Question 3
A points ← 0
B WHILE points > 100000
C MEASURE_POINT()
D points ← points + 1
E ENDWHILE
Line B — points starts at 0, so points > 100000 is false straight away and no points are measured. The condition should be points < 100000 so many readings are taken.
Question 4
A scanner ← LASER
B part ← "car part"
C model ← SCAN3D(part)
D SEND model TO SPEAKER
Line D — A speaker outputs sound and cannot copy an object. To make a copy of the scanned part, the model is sent to a 3D printer.
Question 5
A turntable ← ON
B FOR step ← 1 TO 36
C ROTATE(turntable, 100)
D SCAN()
E NEXT step
Line C — 36 steps of 100 degrees would spin the object far too much and miss detail. Steps of 10 degrees make exactly one full 360 degree turn, so all sides are scanned.

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