"Getting started with Agisoft PhotoScan"

(based on Agisoft PhotoScan standard edition version 0.9.1 build 1693 beta, june 2013)

by Karsten Kiessling

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For this getting started tutorial I have uploaded six photos and the ready processed PhotoScan

project to http://www.diy3dscan.com/ . You are encouraged to follow it and experimenting by

yourselves with the photos and the project . You can get the demo of Agisoft PhotoScan here:

http://www.agisoft.ru/products/PhotoScan/standard/demo/

I have shot these six photos of a small fountain "Bacchus" in the "gardens of the world" in Berlin in

2010. I used my Canon Powershot A590Is for shooting. I know there is room for improving with

better cameras and better light, but for testing purpose it should do it. Btw. the face of Bacchus has

nearly human size, but in opposite to a human it stays perfectly still, has a good texture, no shiny

reflections and no hair.

As you can see later I shot three stereo pairs, one from above the fountain, one in front and one from

below. Keep in mind that for every stereo pair you should use a stereo base to distance ratio from

1/5 to 1/10 (for example 20-10cm stereo base at 1m distance). All photos are aiming to Bacchus and

covering the whole figure so there is very good overlap. Of course you can also shot parts of your

object of interest.

1. Preparing Agisoft PhotoScan

When you start PS (Agisoft PhotoScan) for the first time, you can choose your preferred language

under Tools/Preferences/General

If you have a powerful graphic card you can speed up the depth map generation by using it. Under

the second tab " OpenCL " you should activate your graphic card and deactivate one CPU core for

each GPU in use, like this:

Now you are ready to begin!

Up to now follow the workflow tab from top to down until "Build texture"

2. "Add Photos..."

3. "Align Photos..."

Align them with high accuracy, it generates max. 40 000 points per image and compares these points

for every image combination. From these points PS recalculates the camera calibration parameters

and among other things the camera stations.

use "Pair preselection" generic, nevertheless it is rather for large photo sets to speed up the

processing:

and you get a sparse model from the common 20.000 points from the six images:

Here you can see the three stereo pairs from above, front, and below.

At this point it's time to adjust the bounding box to your object so, that all uninteresting parts and

nothing of the interesting parts are cut off. In "resizing region" mode (cross arrows) you do it by

picking the corner with the left mouse button and move it to the desired position. In "rotating

region" (it's the button to the right) you can rotate your bounding box to a desired position. It is

recommended to use alternately the "navigation" mode (single arrow) to change the point of view

with the left mouse button (drag the red, green and blue circles of the trackball) and with the right

mouse button the position of your object in space:

Just to mention it, you can now further inspecting and edit your project by "Reprojection error",

"Reconstruction uncertainty" and "Image count" under "Edit/Gradual Selection..." ( note that this is

only possible after the aligning step, later this menu is changing):

The calculated camera calibration parameter you can see in "Tools/Camera Calibration"

on the tab "Adjusted"

with the recalculated focal length fx, fy, projection center cx, cy, radial distortion coefficients k1, k2,

k3 and k4 and tangential distortion coefficients p1 and p2 .

When you want, you can export your cameras and undistort your images. See Tools menu/export for

this. In camera export you can chose between a number of formats for importing and using it in

another application:

You can undistort your images with different options:

It is now a good time to save your project with "File/Save As..."!!!

4." Build Geometry..."

For the object type chose Arbitrary. This is for any kind of object; Height field is for modeling planar

surfaces:

- when you chose geometry type "Smooth", little holes are filled with extra geometry so you get a

watertight geometry.

- when you chose geometry type "Sharp" you get a more accurate reconstruction but it needs hole

filling.

When you chose target quality "Ultrahigh" the original resolution of the images is used (results in

very long processing time); "High" height and length of the image divided by two (shorter processing

time, I have chosen this), "Medium" again divided by two (even shorter); "Low" again divided by two

(even faster); "Lowest" again divided by two (fastest)

If you set the "Face count" in the above menu to zero there is no decimation step after "Build

Geometry". This is sometimes really useful. You can edit the calculated geometry by yourselves and

decimate only the needed geometry later.

This is the shaded result after "Build Geometry" step "High" with more than 6 million faces:

After the "Build Geometry" step the menu of the "Gradual Selection" menu has changed to:

with two option to inspect and edit your 3d geometry. With "Connected component size" you can

chose unconnected parts of your geometry and with "Polygon size" you can chose big, extra polygons

created by the smooth geometry building process, which you can erase now.

Here you can see the solid geometry:

When you want to see your object from the near you should change the view options from

"Perspective" to " Orthographic"

After zooming in:

Way to much triangles ,more than 6 million, needing to be decimated with "Tools/Decimate Mesh..."

5. "Build Texture..."

As you can see, you have 5 "Mapping modes". With "Generic" you get this texture (I have used this):

and with "Adaptive orthophoto" you get:

and with "Orthophoto":

In the "Blending mode" you can chose between "Mosaic" (which is the best), Average, Max and Min

Intensity of the images:

Type in your atlas width and height (multiples of 1024, depending on what is possible with your

graphic card and what you want)

And chose the color depth between standard (24 bit) and HDR (96 bit) - I have chosen standard.

Finally you can export your object as model (mesh) in the following formats:

or as point cloud:

There is a lot more in PS like masking, working with chunks, working with a turntable ... but back to

our Bacchus:

When you inspect it, you see that despite the low number of images, the low quality of the camera

and the hard shadows on this sunny day it is pretty good modeled. Of course there are some parts

that aren't so well modeled. These are the tip of the nose and the upper part of the head, which

would had benefit from additional images. So, I hope, you get a feeling of how many images are

necessary and in which configuration you should shot them. One drawback of photogrammetry is

that it is a post processing process and you never know if you have shot enough photos. So it is often

simpler to shot more photos than "necessary" as come back to the location.

Certainly, the water of this fountain isn't modeled at all, because of the time between the shots with

one camera. In the depth maps you can see, that you get the depth of the water too.

So with a multi camera array it should be possible to model that too.

I hope you enjoyed this rather long explanations and it encouraged you to use PhotoScan by

yourselves.

Take your camera with you as your scanner in your pocket!