123D Catch - Tutorial

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Melvyn Sims
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The official site, which includes links to downloads, can be found here http://www.123dapp.

1 123D Catch - Tutorial Autodesk s 123D Catch software (formerly Project Photofly) is based on photogrammetry. Photogrammetry is a process which derives geometric properties of an object from a series of images. 123D Catch is still in beta testing; as such, it will likely continue to improve. The official site, which includes links to downloads, can be found here Video documentation can be found on YouTube regarding the following Photo tips and planning for better results Getting started with uploading images Navigating within a scene Creating Animations Manual Stitching Editing meshes and requesting refined models The chart below shows the general workflow for the process (though labeled for Photofly, it still holds true for 123D Catch) 1

Guidelines for taking images: Decide on a focal length before you start shooting. Once you start, avoid zooming in and out.

shots before you start. Ideally, work consistently from high to low, and from left to right.

of marking system when your subject lacks discernable features.

Consider using a high contrast tape (black gaffer s tape works really well!).

2 Guidelines for taking images: Decide on a focal length before you start shooting. Once you start, avoid zooming in and out. Zooming distorts images and will make it impossible for information to align across a set of images Avoid shiny objects or objects with extreme glare, as these will confuse the system. Mirrored or transparent surfaces are another feature that will cause problems and should be avoided if possible Plan out the order in which you will take shots before you start. Ideally, work consistently from high to low, and from left to right. Keeping your chronology consistent will allow you to identify errors later on (should they arise) when you are working within the software Use some sort of marking system when your subject lacks discernable features. You need 4 points for registration between any one image and two other images in the collection. Consider using a high contrast tape (black gaffer s tape works really well!). Place enough markers so that at least 4 are always visible from any of the positions you plan to shoot from Spacing of shots: ideally every 5 to 10 degrees (though 15 degrees works OK); at least 50% overlap between images Since the information from photos is based on line-of-sight, a single position will severely limit what we collect. Instead, we need to move around (in the case of an object) or across (when dealing with architectural space) our subject. This will help us see what is not visible from a single perspective Fixed point Multiple points Note the hole in the mesh 2

Of particular interest when capturing objects (including heads) Move the

Think of the head as an attractor to the camera lens.

The bottom row should be low enough to capture the bottom of the chin.

good results (a minimum of 40 shots not more than 70) Top view Perspective

3 Of particular interest when capturing objects (including heads) Move the camera position at regular intervals and in a predictable pattern (i.e. from left to right and from top to bottom). Think of the head as an attractor to the camera lens. The top row of images should capture beyond the center of the head (i.e. there should be overlap to ensure complete coverage). The bottom row should be low enough to capture the bottom of the chin. 12 shots per row (16 degrees between shots), and 4 rows seem to produce good results (a minimum of 40 shots not more than 70) Top view Perspective view Side view 3

4 Loading files 1- Open the program. At the starting screen click on Create a new Photo Scene 2- Browse to the set of images you want to use. Select all the images (drag to select or CTL+A) and click Open. 4

Scene Name with something more descriptive if you like).

5 3- Back at the opening screen, click Compute Photo Scene. In the dialogue box that appears, make sure your is visible and correct, and click Me (you can also append the Photo Scene Name with something more descriptive if you like). You will receive an when your files are ready (anywhere from 10 minutes to perhaps an hour). Creating a Scene 1- You will receive an from Autodesk with a link to your prepared file. Download the file. Open 123D Catch. At the start screen, click on Open an Existing Photo Scene. 5

6 2- Browse to the file you just downloaded from your 3- You should now see your scene. Navigation is pretty straight forward: Pan = Click middle mouse and drag Rotate = Shift + Click middle mouse and drag 3D geometry Camera positions Thumbnail Images 6

highlight this information) Projected image from current camera Current camera Clicking on an image will reorient the view to show things from that camera s perspective.

7 Note the line connecting the camera locations above. This shows the chronology of the images taken. Hovering over an image will highlight the corresponding camera position and its contribution to the overall geometry in the main window as a projected image (hovering over a camera will also highlight this information) Projected image from current camera Current camera Clicking on an image will reorient the view to show things from that camera s perspective. To return to the global view, press space bar. Scroll along the bottom to view the thumbnails for all your images. If any of these are darkened, it means that the program had trouble automatically aligning them with the others (in this program, aligning is called stitching ). If none of the thumbnails look darkened, you can skip the stitching steps below and go to the next section, Choosing Mesh Quality. 7

8 Stitching 1- Double-click on darkened images to open the manual stitching window Unstitched image Reference images 8

9 2- You need to find 4 common points on the unstitched image and on two reference images (reference images are any images in the set that have previously been stitched). Notice that the 2 default reference images may not be ideal. You can choose alternate images by clicking on the arrows in either of the reference images. In this example, I kept the top reference but changed the bottom one to something more similar 3- In the unstitched image, left-click and drag until you see a magnified preview with crosshairs. Choose a feature that is clearly visible in all three images (I used black target tape). A yellow round icon will appear, indicating the point has been established. To move a previously placed target, simply drag from its location. You can also right-click to delete targets. 9

4- Repeat this for the two reference images sometimes after placing the first two targets, a yellow square icon will automatically appear in the third window The square icon is the program s way of

10 4- Repeat this for the two reference images sometimes after placing the first two targets, a yellow square icon will automatically appear in the third window The square icon is the program s way of telling you that it has an idea of where the reference on the third image will go. Click on the box icon to accept this location. The reference points should now turn green and you will see 1 of 4 point matched at the bottom right. 10

5- Continue this process until you have referenced 4 points across the 3

Note the four points in each image are green Four points have been

new alignment to take place, the file will need to be uploaded to the

11 5- Continue this process until you have referenced 4 points across the 3 images. Note the four points in each image are green Four points have been established, so stitching is complete for this image 6- In order for the new alignment to take place, the file will need to be uploaded to the server. If you have just one unstitched image in your scene, you can click on submit. The program will minimize while the transfer takes place 11

If you have more than one unstitched image, you may want click on continue. This will allow you to stitch additional images. You can then submit multiple images all at once at the end of the process.

12 If you have more than one unstitched image, you may want click on continue. This will allow you to stitch additional images. You can then submit multiple images all at once at the end of the process. Regardless, after stitching, the file will go to the cloud for regeneration and will then be sent back to you. Choosing Mesh Quality The following assumes that either (a) you didn t have to stitch anything and are working with the original scene file; or (b) you performed stitching (as outlined above), sent the file to the cloud server for updating, and have opened the updated version after it has been ed back to you... Up to this stage, we have been looking at the data at very low resolution (in DRAFT mode). You will want to increase resolution for final use. Click at the top right on the Mesh Quality: DRAFT button to pull up the quality options Select one of the three settings (Maximum is probably best for our purposes, but will take the longest to process). Below is a comparison of the three levels of Mesh Quality, all derived from the same original scene and imported into Rhino as OBJ files 12

13 Poly count File Size Mobile 29, MB Standard 112, MB Maximum 372, MB Mobile Standard Maximum Upon selecting the Mesh Quality setting, the program will again shut down while the scene is uploaded to the server. When done, go to your , download the file and open the new scene. 13

Cleaning up the mesh You may want to delete background

To do so, simply click and drag in an empty area of the

By default, this gives you a lasso-type selection.

14 Cleaning up the mesh You may want to delete background mesh information or unwanted areas in general. To do so, simply click and drag in an empty area of the background. By default, this gives you a lasso-type selection. Selected mesh faces will turn red. To delete a selection, press your delete. To deselect, click a second time. 14

Exporting To export the file to something we can import

The resulting OBJ file can be opened in just about any

15 Exporting To export the file to something we can import into 3D modeling software, you need to export using a 3D format. Go to File>Export Scene As Choose OBJ as the file type. The resulting OBJ file can be opened in just about any modeling program Note that when you export to OBJ, a JPEG file is created for the textures. In order to render with color, you will need to keep the OBJ and the associated JPEG together in the same folder. I.e. 15

16 + = Viewed in Rhino using Rendered mode 16

A Guide to Processing Photos into 3D Models Using Agisoft PhotoScan

A Guide to Processing Photos into 3D Models Using Agisoft PhotoScan Samantha T. Porter University of Minnesota, Twin Cities Fall 2015 Index 1) Automatically masking a black background / Importing Images.