How to create a perfect 3D scan

TLDR

A perfect object's surface for photogrammetry looks something like this:

• thousands of distinct/random features
• no specular highlights
• no blurry areas
• high contrast

Guide

It is all about the object's surface and some basic camera and lighting settings. But fortunately, there are some neat little tricks to scan almost any kind of object. The following flow chart gives an overview and should be printed and placed next to your scanner.

Every new object poses a challenge, so take your time answering each individual question and adjust your workflow accordingly

Below you can find many examples and explanations.

Table of Contents

1. OBJECT
2. Plastic Miniature
3. Plastic replacment part
4. Plastic 3D printed miniature
5. Metal Key
6. Cast Metal Tank Chain
7. Stone spinning whorl (archeology)
8. Flintstone tool/weapon
9. LIGHT
10. Cross polarization
11. CAMERA

OBJECT

I am using either the OpenScan Classic or Mini with the ring light turned on to create the following examples:

Plastic miniature

bad	bad	very good
without polarizer	with polarizer	with polarizer and scanning spray
The object has large unicolor areas and a lot of specular highlights	The specular highlights can be removed with cross-polarisation (which is not absolutely necessary, but helps in the next step)	Add thousands of tiny dots by applying a fine layer of scanning/chalk spray, the dots could be finer and denser.

Plastic replacement part

bad	okay-ish	perfect
without polarizer	with polarizer	with polarizer and scanning spray
The object seems to have a lot of surface features, where in fact it is almost totally unicolor. What you see here are thousands of specular highlights	The specular highlights can be removed with cross-polarisation. Now, you are able to see, that the object is almost completely featureless (except for some small pieces of dirt, which might already be enough.)	Add thousands of tiny dots by applying a fine layer of scanning/chalk spray. This is an example of a perfectly random, feature-rich surface

Plastic 3D Printed miniature

bad	bad	perfect
without polarizer	with polarizer	with polarizer and scanning spray
Again, the surface seems feature-rich, but all you see are specular highlights created by the surface of the 3d print	As soon as you add cross-polarization, all those highlights disappear and not many features are left	Create a perfect, feature-rich surface with the help of some scanning spray

metal key

bad	bad	good
without polarizer	with polarizer	with polarizer and scanning spray
lots of specular highlights and almost no distinct surface features	due to the high reflectivity of the surface, there are still specular highlights visible when using cross-polarisation (this could be avoided in a completely dark environment + polarized light source)	adding dots helps a lot to create enough features, but the remaining specular highlights might create some noise in the resulting 3d mesh. To improve the result, you would have to matte the surface before applying the scanning spray

Cast metal tank chain

bad	very good
without polarizer	with polarizer

Stone spinning whorl

This is basically as good as it could be, lots of features and almost no specular highlights. Note, that not all types of stone show that amount of surface features/graininess.

perfect	perfect
without polarizer	with polarizer

Stone flintstone tool

bad	good
without polarizer	with polarizer
A lot of specular highlights	The feature on this surface are not very distinct and a little bit washed-out. Scanning spray could definitely help a lot

Wood

This is basically as good as it could be, lots of features and almost no specular highlights. Note, that not all types of wood show that amount of surface features/graininess.

perfect	perfect
without polarizer	with polarizer

Fabric

Skin

LIGHT

Cross-polarization

CAMERA