These tutorials will show you how to digitize archaeological features from terrestrial scan data.
Hint: You can click on any image to see a larger version.
 

Drawing with the spline tool

In some cases using the pencil tool is not convenient. Cases include places where there are unhealed holes in the mesh and places where individual points need to be places in close proximity to one another in an irregular pattern. Any drawing will likely involve both the pencil and spline tools.

[wptabs style=”wpui-alma” mode=”vertical”] [wptabtitle] THE SPLINE TOOL[/wptabtitle] [wptabcontent]Select the “Spline” tool from the “3d Mesh Sketch” Menu

Fig. 31: The Spline tool[/wptabcontent]

[wptabtitle] NAVIGATE WITH THE SPLINE TOOL[/wptabtitle] [wptabcontent]As with the pencil tool, zoom in and navigate through the mesh to obtain a good view of the area you are digitizing. Place individual vertices at the desired locations on the mesh. The current vertex will be circled. Both vertices and the polyline will be drawn as they are created.

Fig. 32: Drawing a spline on a mesh.[/wptabcontent]

[wptabtitle] RENDERING DURING NAVIGATION[/wptabtitle] [wptabcontent]The mesh will be rendered as a point cloud during navigation.

Fig. 33: Navigating while in spline drawing mode.[/wptabcontent]

[wptabtitle] CHECK SPLINE ALIGNMENT[/wptabtitle] [wptabcontent]Zooming out provides an opportunity to check that new features align well with previously created ones, and that the overall interpretation is coherent.

Fig. 34: Checking the coherence of a group of splines. [/wptabcontent]

[wptabtitle] COMMIT EDITS[/wptabtitle] [wptabcontent]Commit edits to the “Spline” tool by clicking on the “Check” box.

Fig. 35: Committing edits for the spline tool. [/wptabcontent]

[wptabtitle] ADD MORE SPLINE SEGMENTS[/wptabtitle] [wptabcontent]To add further continuous segments, continue to use the “Spline” tool. Hover the mouse over the endpoint and it will be highlighted with a dashed circle around it. Clicking will snap the first point of a new polyline to the highlighted endpoint.

Fig. 36: Snapping with the spline tool. [/wptabcontent]

[wptabtitle] SPLINE TOOL VS. PENCIL TOOL[/wptabtitle] [wptabcontent]Comparing the Pencil and Spline tools

The Spline Tool

-Advantages: Using the spline tool you can place vertices in meaningful locations and have more control over the form of the final vector.

-Disadvantages: This method is slower than using the pencil tool and requires frequent navigation in the point cloud to ensure you are picking good points for vertex placement.

The Pencil tool

-Advantages: Significantly faster drawing and snapping to faces on the mesh, continuous point generation.

-Disadvantages: If there are holes in your mesh, the vector created by the pencil can more easily ‘fall through’ those holes, creating wild loops.

[/wptabcontent]

[wptabtitle] ADDING ANNOTATIONS[/wptabtitle] [wptabcontent]To insert text annotations into the model, enter the 3D sketch mode by selecting the 3D Sketch button from the main menu.

Then select the Text button.

Left click at the desired location to insert the text. Adjust options for size and font as desired.

n.b. The Rapidform freeviewer provides more flexible options for inserting annotations. It may be preferable to complete this step of the process using the freeviewer. More information on annotating models can be found in the Rapidform Freeviewer workflow.

Fig. 37: Adding text annotations.

[/wptabcontent] [/wptabs]

These tutorials will show you how to digitize archaeological features from terrestrial scan data.
Hint: You can click on any image to see a larger version.
 

[wptabs style=”wpui-alma” mode=”vertical”][wptabtitle] THE 3D MESH SKETCH TOOLBAR[/wptabtitle] [wptabcontent]Select the 3D Mesh Sketch toolbar.

Fig. 23: The 3D Mesh Sketch Menu.

And then select the “Pencil” tool

Fig. 24: The Pencil button.[/wptabcontent]

[wptabtitle] TOGGLE BETWEEN NAVIGATION AND DRAWING[/wptabtitle] [wptabcontent]Click the center mouse button to toggle between Navigation and the Pencil tool.
[/wptabcontent]

[wptabtitle] DRAWING WITH THE PENCIL TOOL[/wptabtitle] [wptabcontent]Zoom in and navigate so that you can clearly see the polyfaces where you wish to place a boundary. The selected polyface will be highlighted in yellow.

Fig. 26: Drawing with the pencil tool.

Think carefully about whether you want to place boundaries on ‘top’ of an edge, in ‘front’ of an edge or on the edge itself. [/wptabcontent]

[wptabtitle] WILD LOOPS![/wptabtitle] [wptabcontent]

Fig. 27: Pencil tool errors include the creation of undesired loops in polylines.

Be aware of holes remaining in the mesh. Drawing across a hole in the mesh with the pencil tool will result in a ‘wild loop’ where the polyline falls through the hole. [/wptabcontent]

[wptabtitle] DRAGGING POLYLINE VERTICES[/wptabtitle] [wptabcontent]

Fig. 28: Dragging polyine vertices.

When you have completed drawing a polyline surrounding a ‘closed’ shape, you may need to drag one of the endpoints to snap to the start of the polyline. Select the endpoint by left clicking on it and drag until the target point is highlighted.[/wptabcontent]

[wptabtitle] CHECK YOUR POLYLINES[/wptabtitle] [wptabcontent]

Fig. 29: Checking a polyline-mesh alignment.

Check your polyline from multiple viewpoints to make sure it intersects the desired polyfaces in the mesh.[/wptabcontent]

[wptabtitle] ADJUST YOUR POLYLINES[/wptabtitle] [wptabcontent]You can alter the polyline by selecting individual nodes and dragging along the mesh.

Fig. 30: Adjusting a polyline to match the mesh.

n.b. Be aware that when you drag the endpoint, or any vertex, on a polyline, you alter the shape of the entire line, and slightly shift all the vertices. Be sure to check that the overall placement of the polyline is satisfactory after making adjustments to any given vertex.[/wptabcontent]

[wptabtitle] Continue to the Spline Tool[/wptabtitle] [wptabcontent]In some cases using the pencil tool is not convenient. Cases include places where there are unhealed holes in the mesh and places where individual points need to be places in close proximity to one another in an irregular pattern. Any drawing will likely involve both the pencil and spline tools.

Continue to the Drawing with the Spline Tool.

[/wptabcontent][/wptabs]

These tutorials will show you how to digitize archaeological features from terrestrial scan data.
Hint: You can click on any image to see a larger version.
 

[wptabs style=”wpui-alma” mode=”vertical”] [wptabtitle] AN UNCLEAN MESH[/wptabtitle] [wptabcontent]If the mesh has many holes, as seen in the one below, it is worthwhile to repair the mesh.

Fig. 18: An unclean mesh sporting holes and manifold faces.[/wptabcontent]

[wptabtitle] ENTER THE MESH EDITING MODE[/wptabtitle] [wptabcontent]Push the “Mesh” button to enter the mesh editing mode.

Fig. 19: The Mesh mode button[/wptabcontent]

[wptabtitle] THE FILL HOLES BUTTON[/wptabtitle] [wptabcontent]Select the “Fill Holes” button.

Fig. 20: The Fill Holes button[/wptabcontent]

[wptabtitle] FILL HOLES PARAMETERS[/wptabtitle] [wptabcontent]Left click and drag to select the area for which you wish to fill holes. Adjust the options in the menu on the left to exclude any holes which should persist. The “Do Not Fill N-Biggest Holes” and “Do Not Fill If Hole is Bigger Than” options are particularly useful. Holes which will be filled are highlighted in bright blue.

Fig. 21: The Fill Holes parameters menu [/wptabcontent]

[wptabtitle] THE HEALING WIZARD[/wptabtitle] [wptabcontent]If RapidForm is unable to fill some of the holes, try applying the “Healing Wizard”, doing some manual cleaning of the mesh, and then try filling the holes again.

Fig. 22: The Healing Wizard Menu.

Tiny defects in the mesh, like the one shown highlighted in green, prevent holes from being closed.

n.b. Making a clean and watertight mesh can be a time consuming process, especially for complex, natural forms. If your project’s deliverables do not include the mesh, it may be pragmatic to allow some imperfections to remain and to work around them while digitizing. If the mesh is part of the project’s deliverables, be sure to budget sufficient time for this step in the process.

[/wptabcontent]

[wptabtitle] CONTINUE TO…[/wptabtitle] [wptabcontent]You can now continue to Digitings using the Pencil Tool in Rapidform[/wptabcontent]
[/wptabs]

These tutorials will show you how to digitize archaeological features from terrestrial scan data.
Hint: You can click on any image to see a larger version.
 

These tutorials will show you how to digitize archaeological features from terrestrial scan data.
Hint: You can click on any image to see a larger version.

• This tutorial uses RapidForm XOR
• Hint: Click on any image to view a larger version.

[wptabs style=”wpui-alma” mode=”vertical”] [wptabtitle]SUBSETTING MESHES IN RAPIDFORM[/wptabtitle]
[wptabcontent]Part of the GMV Rapidform Modeling Series

[/wptabcontent]
[wptabtitle]ACHIEVING MANAGEABLE FILE SIZES[/wptabtitle]
[wptabcontent]
-The meshes produced through terrestrial laser scanning and close range photogrammetry can be very large.

-To facilitate working with the data, it is sometimes useful to subset or reduce the density of the dataset. The desired dataset size might be described through the polyface count, number of vertices, or file size per model.

-Subsetting a mesh will reduce the size of each individual file while maintaining the full resolution of the data, while decimating will reduce the data resolution but avoids splitting the data across several files.
[/wptabcontent]
[wptabtitle]THE SPLIT COMMAND[/wptabtitle]
[wptabcontent]Subsetting a mesh in Rapidform is simple.

– Enter the Mesh Mode by double clicking on the mesh you would like to subset in the left-hand menu tree.

– From the top menu select the Split command.

[/wptabcontent]
[wptabtitle]CHOOSE A SPLIT METHOD[/wptabtitle]
[wptabcontent]
In the Split command sub-menu select Method – By User Defined Plane. Select the base plane that will split your mesh nicely. Under Plane Options go to Base Plane.

[/wptabcontent]
[wptabtitle]ROTATE THE PLANE TO SPLIT THE MESH[/wptabtitle]
[wptabcontent]
– Move and Rotate the plane until it is in the proper position to split the mesh.

[/wptabcontent]
[wptabtitle]SPLIT THE MESH[/wptabtitle]
[wptabcontent]
– The Dialog will list the remaining region and it will be highlighted on the screen. Hit the continue arrow to split the mesh

[/wptabcontent]
[wptabtitle]SELECT THE REMAINING REGION[/wptabtitle]
[wptabcontent]
– Select the Remaining Region which will appear highlighted in blue (or yellow if you hover over it with the mouse) and hit the check button to accept the results.

[/wptabcontent]
[wptabtitle]EXPORT THE RESULTS[/wptabtitle]
[wptabcontent]
– Export the resulting section of the mesh as a new file to save the result of the process.

Congratulations! You’re Done!
[/wptabcontent] [/wptabs]

Download this tutorial as a pdf.
[iframe src=”/wp-content/uploads/2012/02/rapidform_arch_plans.pdf” width = “800px” height = “500px”]

I. Introduction

A. Comparing two meshes is a common task in 3d modeling applications. A model created from laserscanning data might be compared with a model created from photogrammetric data to assess relative accuracy. A building’s façade might be documented with a laserscanner at six month intervals to monitor erosion by comparing the meshes and individual profiles over time. This workflow demonstrates how to carry out a comparison in Rapidform XOR.

II. Aligning Models

A. Models with surveyed targets

1. In the Main Menu in Rapidform go into Tools > Scan Tools > Align between Scan Data.

Fig. 1: Align between Scan Data Menu

2. Select the Local Based on Picked Point method and select your Reference and Moving targets- the two meshes you are trying to align.

3. Check the box to Refine Alignment.

Fig. 2: Select reference and moving meshes

4. Zoom in close to each target and select it, first in the Reference and then in the Moving model. Right click to toggle between zooming and selection modes. Be sure to select the center of the target as accurately as possible. A colored pin will appear showing the picked center of each target

Fig. 3: Pick point on corresponding targets in the moving and reference meshes.

5. Once all the targets have been matched, you can visually review the goodness of the fit between the models by looking at the distance between the pins shown in the left hand window in this menu. When you are satisfied, check the Align Between Scan Data box to complete the process. The alignment will be refined.

Fig. 4: When the meshes are aligned, complete the transformation.

B. Models without targets

1. Aligning models without targets is inherently less accurate than alignments done based on surveyed targets because points on natural surfaces must be matched. Because the natural surfaces -as they are modeled- have slight local deviations, the algorithms used for fitting the models together can encounter problems.

2. The process is essentially the same as aligning models with surveyed target, but with the additional requirement of selecting good targets on natural surfaces to achieve a closely aligned match. Follow the instructions in A1, A2 and A3.

3. Select points with high local curvature – edges and corners ideally- or intersections of linear features. Try to pick at least six points. When you are satisfied, check the Align Between Scan Data box to complete the process. The alignment will be refined.

Fig.5: On natural surfaces pick points on well defined features.

III. Assessing Differences between two Meshes

A. Mesh Deviations

1. In the Main Menu in Rapidform, select Measure > Mesh Deviations.

2. Select the meshes you are interested in as the Target Entities.

Fig. 6: The Mesh Deviations Menu

3. On the right hand side of the screen, set the Allowable Tolerance as the acceptable deviation between the meshes. Adjust the Color Bar to reflect the expected range of deviations between the meshes. Under Type select the appropriate deviation for your application, Max. Deviation is recommended for erosion monitoring. Click the ! under Deviation Option to recalculate the range.

Fig. 7: Properties of a mesh deviations map

4. Click the right arrow button in the Mesh Deviations menu to show the deviation overlaid on the mesh

Fig. 8: Mesh deviations displayed over the mesh.

The meshes produced through terrestrial laser scanning and close range photogrammetry can be very large. To facilitate working with the data, it is sometimes useful to subset or reduce the density of the dataset. The desired dataset size might be described through the polyface count, number of vertices, or file size per model. Subsetting a mesh will reduce the size of each individual file while maintaining the full resolution of the data, while decimating will reduce the data resolution but avoids splitting the data across several files.

[wptabs style=”wpui-alma” mode=”vertical”]

[wptabtitle] GETTING STARTED[/wptabtitle]

[wptabcontent] Subsetting Mesh Data

Subsetting a mesh in Rapidform is simple.

1. Enter the Mesh Mode by double clicking on the mesh you would like to subset in the left-hand menu tree.

2. From the top menu select the Split command.

Fig. 1: The Split tool[/wptabcontent]

[wptabtitle] THE SPLIT COMMAND[/wptabtitle]

[wptabcontent]3. In the Split command sub-menu select Method – By User Defined Plane.

Select the base plane that will split your mesh nicely. Under Plane Options go to Base Plane.

Fig. 2: Select a base plane.[/wptabcontent]

[wptabtitle] MOVE AND ROTATE THE PLANE[/wptabtitle]

[wptabcontent]4. Move and Rotate the plane until it is in the proper position to split the mesh.

Fig. 3: Manipulate the base plane.[/wptabcontent]

[wptabtitle] CLICK CONTINUE ARROW[/wptabtitle]

[wptabcontent]5. Hit the continue arrow to split the mesh

Fig. 4: Select the region you wish to preserve. [/wptabcontent]

[wptabtitle] EXPORT[/wptabtitle] [wptabcontent]6. Select the Remaining Region which will appear highlighted in blue (or yellow if you hover over it with the mouse) and hit the check button to accept the results.

Fig. 5: The results of a split operation

7. Export the resulting section of the mesh as a new file to save the result of the process.[/wptabcontent]

[wptabtitle] DECIMATE IF NECESSARY[/wptabtitle]

[wptabcontent]III. Decimating a mesh

In addition to subsetting the mesh, you may want to decimate it to further reduce file size.

1. While in mesh editing mode select the Decimate tool from the top menu bar

Fig. 6: The Decimate Tool[/wptabcontent]

[wptabtitle] DECIMATING CONT.[/wptabtitle] [wptabcontent]2. In the Decimate tool menu, select Poly-Face Count and then set the Reduction Ratio or the Target Poly-Face Count. The level of reduction will obviously depend on your project’s requirements. For import into ArcGIS (see the workflow) a target poly-face count of fewer than 500,000 is recommended. Select Large Data Mode, Preserve Color and Do not Move Poly-Vertices, set the High Curvature Area Resolution toward Dense, and hit the check button.

Fig. 7: Decimate the Mesh
The options in this menu are explained fully in the Rapidform Contextual Help.

3. Export the decimated mesh to save it as a new file.[/wptabcontent][/wptabs]

Many archaeological projects use a GIS to manage their data. After terrestrial scan or photogrammetric modeling data has been collected and cleaned, it may be convenient to integrate it into a project’s GIS setup. As ArcGIS is widely available and in use both in University research departments and government offices, we’re using it for the example here, but something like this should work for other GIS packages.

The first part of the workflow addresses working with meshes created from terrestrial scan data, and assumes you have existing meshes in Rapidform.

[/wptabcontent]

[wptabtitle] Decimation[/wptabtitle] [wptabcontent]

Before exporting a dataset for use in a GIS you may want to decimate the dataset to produce a lower resolution model for visualization. High resolution models can slow rendering down and make manipulation of the model difficult.

a. Select the model you will be exporting either graphically or through the menu tree on the left hand side of the screen.

b. In the main menu select Tools and then Scan Tools and Decimate Meshes

Fig. 1: Select the Decimate Meshes tool

c. In the Decimate Meshes menu confirm the selection of the Target Mesh.

d. Under Method choose Poly-Face Count for best control over the size of the resultant model.

e. Under Options set the Target Poly-Face Count. Numbers under 100,000 will render relatively quickly in ArcGIS. Inclusion of more than 500,000 polyfaces is not recommended.

f. Under More Options select Preserve Color.

g. Click “OK” to confirm and decimate the mesh.

Fig. 2: Select options for decimating the mesh.

[/wptabcontent]

[wptabtitle] Subsetting and Splitting Meshes[/wptabtitle] [wptabcontent]

(Skipping ahead a bit conceptually…) When you import your mesh data into ArcGIS each mesh is stored as a single multipatch. You don’t want to edit the shape of the multipatch in ArcGIS, only the placement (trust us on this). So any subsetting of the mesh needs to be performed before exporting from Rapidform (or other modeling software of your choice). Why subset or split a mesh?

a. Navigating in tight, enclosed spaces. You might want to be able to turn off the visibility of the back wall of a room or one half of a cistern to better visualize its interior.

b. Major sections of a mesh. If you have a scan of a building including several rooms or structures and you want to be able to visualize them individually, then they need to be made into discrete meshes.

[/wptabcontent]

[wptabtitle] Exporting[/wptabtitle] [wptabcontent]

a. Select the model you want to export from the menu tree on the left hand side of the screen.

b. Right-click and select “Export”. Select an appropriate file format (see step 2, below, for choices).

Fig. 3: Export via the menu tree.

4. Export Formats

a. Get a list of valid export formats by looking in the dropdown menu of the export dialog box.

Fig. 4: Valid export file formats.

b. Suggested formats for export are VRML (file extension .wrl), collada (.dae) and AutoDesk 3d Max (.3ds).

[/wptabcontent][wptabtitle] Advice on Textures and Color Data[/wptabtitle] [wptabcontent]

Modeling software manages color data in several ways. Color data might be recorded as UV coordinates referencing a separate texture file, as per vertex, per face or per wedge color information. Color data imported with scan data will typically default to storage as per vertex color. ArcGIS only recognizes color data stored explicitly in texture files, so if your color data is currently stored in another form you need to convert it.

[/wptabcontent]

[wptabtitle] Textures direct from Rapidform[/wptabtitle] [wptabcontent]

i. Select the Mesh mode from the main toolbar.

ii. Select Tools and Texture Tools and Convert Color to Texture.

Fig. 5: Conver Color to Texture

iii. After creating the texture, export the model as usual.

iv. Export the texture by going in the Main Menu to Texture Tools, then Export Texture to save the texture file. Store it in the same folder as the model.[/wptabcontent]

[wptabtitle] Color and Texture in Meshlab[/wptabtitle] [wptabcontent]Sometimes you want more tools for color editing. Sometimes ArcGIS doesn’t like the textures produced by Rapidform. For this reason, we suggest an alternative method for setting the texture data using Meshlab. Meshlab is open source, and can be found at meshlab.sourceforge.net.

i. From Rapidform export a .VRML file by right-clicking (in the model tree menu on the left land side of the screen) on the mesh you wish to export and selecting Export.

ii. In Meshlab, open a new empty project. Go to File and Import Mesh.

Fig. 6: Import the Mesh to Meshlab

iii. Select the VRML file you just created and hit Open.

iv. Transfer the color information from per vertex to per face. In the main menu go to Filters, then to Color Creation and Processing, then to Transfer Color: Vertex to Face. Hit Apply in the resulting pop-up menu.

Fig. 7: Transfer color data from the vertices to the faces of the mesh.

v. From the Main Menu go to Filters, then to Texture, then to Trivial Per-Triangle Parametrization.

Fig. 8: Create texture data.

In the pop-up menu, select 0 Quads per line, 1024 for the Texture Dimension, and 0 for Inter-Triangle border. Choose the Space Optimizing method. Click Apply.

n.b. If you get an error along the lines of “Inter-Triangle area is too much” your Texture Dimension is too small for the dataset. Increase the texture dimension to resolve the error.

Fig. 9: Set the texture data parameters.

vi. In the Main Menu go to Filters and Texture and Vertex Color to Texture. Accept the defaults for the name and size. Tick the boxes next to Assign texture and Fill Texture.

Fig. 10: Transfer color data to the texture dataset.

vii. In the Main Menu go to File and Export Mesh. Make sure to UNTICK the box next to Vertex Color. Otherwise ArcGIS gets confused! Make sure the texture file is present. Click OK to save.

Fig. 11: Export the mesh as collada (dae).[/wptabcontent]

[wptabtitle] Preparing a GIS to receive Mesh data[/wptabtitle] [wptabcontent]

Once you have created your mesh files and exported them to collada or something similar and explicitly assigned texture data (not to be confused with vertex color, face color or wedge color data), you are ready to import the data into ArcGIS. Assuming your data is not georeferenced, follow the method below. If your data is georeferenced, head over to our Photoscan to ArcGIS post, and follow the import method described there.

1. Preparing the geodatabase

a. Open ArcCatalog any way you choose. Create a new geodatabase by right clicking on the folder where you wish to create the geodatabase and selecting New and File Geodatabase. Only Geodatabases support the import of texture data, so don’t try and use a shapefile.

Fig. 14: Create a geodatabase in ArcGIS.

b. Create a multipatch feature class in the geodatabase.

c. Ensure that the X/Y domain covers the coordinates of any meshes you will be importing. View the Spatial Domain by right-clicking on the feature class and going to Properties and then to the Domain tab.

Fig. 15: Check the spatial domain of the new feature class.

d.If the spatial domain is not suitable, adjust the Environment settings by going to the Geoprocessing toolbar in the Main Menu. Scroll down to Geodatabase Advanced and adjust the Output XY Domain as needed. You can also adjust the Z Domain in this dialog box.

Fig. 16: Adjust the spatial domain in the environment settings.

[/wptabcontent]

[wptabtitle] Preparing the scene file. [/wptabtitle] [wptabcontent]

a. Open ArcScene and add base data such as a plan of the site, an air photo of the location, etc. The base data will allow you to control the location to which the model is imported. Add the empty multipatch feature class you just created.

Fig. 17: Add base data to a Scene.

b. Start editing either from the 3D editor toolbar or by right-clicking on the multipatch feature class in the Table of Contents and choosing Edit Features and Start Editing.

Fig. 18: Start editing in ArcScene. [/wptabcontent][wptabtitle] Importing the Scan data[/wptabtitle] [wptabcontent]

1. Import the vrml or collada file by selecting the Create Features Template for the multipatch and clicking on the base plan roughly in the location where you would like the mesh data to appear. Select the vrml or collada file from the Open File dialog box that appears. Wait while the file is converted.

Fig. 19: The vrml data is converted to multipatch on import.

2. You can now Move, Rotate, Scale the imported multipatch in ArcScene by selecting the feature using the Edit Placement tool and inputting values in the 3D Editing toolbar or by interactively dragging the multipatch feature.

Fig. 20: Select the multipatch feature to adjust its position and scale.

3. Once you are satisfied with the placement of the multipatch, you can add attribute data.

[/wptabcontent]

[wptabtitle] A note on rotation in Arcscene[/wptabtitle] [wptabcontent]

You can only rotate in the x-y plane (that is, around z-axis) in ArcScene. If you need to rotate your data around the x or y axis you need to do this in your modeling software before import. Bringing a .dxf of the polygon or point data you are trying to align the mesh with into your modeling software is probably the simplest way to get the alignment right. You may have to translate your .dxf to a local grid because most modeling software doesn’t like real world coordinates. Losing the real coordinates during this step doesn’t matter because you’re just using the polygon data to set orientation around the x and y axes. You’ll get the model in the correct real-world place when you import into ArcScene.

[/wptabcontent]

[wptabtitle] Re-exporting[/wptabtitle] [wptabcontent]

Fig. 21: The textured mesh data appears over the correct location on the base plan.

4. At this point it’s probably a good idea to re-export a collada model of your newly scaled and located mesh data. If not, every time you update the model you will have to go through the scaling and locating process again.

a. In ArcToolbox go to Conversion Tools> To Collada> Multipatch To Collada.

Fig. 22: Export Multipatch to Collada

b. Select the multipatch for export and the folder where you want the re-exported model to appear.

Fig. 23: Set parameters for export.

c. Check that the model has exported correctly by opening it in your modeling software.

n.b. You may have to reapply the textures at this point.

[/wptabcontent]

[wptabtitle] A note on features for attribute management [/wptabtitle] [wptabcontent]

It may be convenient to store attribute information in other related feature classes so that a single meshed model can have multiple, spatially discrete attributes. How you design your geodatabase will vary greatly dependent on project requirements.

Fig. 19: Additional related feature classes can be used to manage attribute data.

[/wptabcontent]

[wptabtitle] A note on just how much mesh data you can get into ArcScene.[/wptabtitle] [wptabcontent]

1. If you are using a file geodatabase, in theory the size of the geodatabase is unlimited and you can include all the mesh data you want.

2. In practice, individual meshes with more than 200,000 polygons have problems importing on an average desktop computer.

3. In practice, rendering becomes slow and jumpy with more than 200 MB of mesh data loaded into a single scene on an average desktop computer. The size and quality of your textures will also have an impact here. Compressed textures are probably a good plan.

4. In short, the limitation is on rendering and on what can be cached in an individual scene, rather than on storage in the geodatabase. Consider strategies including having low polygon count meshes for display in a general scene, with links to high polygon count meshes, which can be stored in the geodatabase but not normally rendered in the scene, which can be called up via links in html popup, the attribute table, or via another script.

[/wptabcontent]

[/wptabs]

General Considerations

Automatic feature recognition has improved greatly (and continues to improve) but isn’t quite up to most archaeological scenarios just yet. It follows that hand drawing, or ‘digitizing’, individual stones, patches of conservation materials, layers of mortar, etc. on scan data is part of many a project’s workflow. For information on drawing 3D vectors on scan data see Part 1 of the Rapidform GMV series.

For purposes of paper publications, sometimes it is convenient to produce a 2D rendering of a 3D object or feature. In archaeology sections, profiles, plans and elevation drawings are commonly used 2D renderings. The 3D vectors characterized from scan data can be converted into 2D drawings. When a 3D dataset is converted to a 2D plan drawing conventions (e.g. line styles, shadings, and hatchings) become essential for conveying information. Conversion is therefore a two-step process; first accurate 2D projections of the 3D vectors describing the feature or object are created, then appropriate drawing conventions are applied. The first stage is easily achieved in Rapidform. The second stage is better accomplished within a CAD, GIS or illustration program which provides finer control over the line artwork.

[wptabs style=”wpui-alma” mode=”vertical”]

[wptabtitle] OPEN A PROJECT[/wptabtitle]

[wptabcontent]Basic Workflow to create a 2D plan from existing 3D vectors in Rapidform

1. Open a project containing your scan data and 3D vectors.

Fig. 1: A Rapidform project with 3D vectors outlining individual stones in a wall.

[/wptabcontent]

[wptabtitle] CREATING A REFERENCE PLANE 1[/wptabtitle] [wptabcontent]

2. Create a reference plane where you want your 2D vectors to appear. Many archaeological features don’t have an obvious, neatly planar ‘top’ or ‘front’ face. Try to orient the reference plane parallel to the main orientation of the feature you are drawing. When choosing the orientation, you may want to consider placing perpendicular reference planes for the creation of a top plan or another elevation or section at the same time.

Fig. 2: This wall is substantially vertical but the front face, as seen from the path, is clearly not a flat plane.

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[wptabtitle] CREATING A REFERENCE PLANE 2[/wptabtitle] [wptabcontent]

a. From the main menu, select “Insert” and from the dropdown menus select “Ref. Geometry” and then “Plane”.

Fig. 3: Select Insert Reference Plane.

b. In the Add Ref. Plane menu a number of options are available for creating the plane. For the creation of an initial plane oriented in line with a set of features, the “Extract” option may be the simplest choice.

Fig. 4: Select a method for defining the reference plane.

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[wptabtitle] CREATING A REFERENCE PLANE 3[/wptabtitle] [wptabcontent]

c. Select the entities you wish to include in the plan by left-clicking and sweeping the mouse across the entities.

Hint: Remember that the middle button on the mouse toggles between navigation and selection.

Fig. 5: Select options within the Add. Ref Plane menu.

d. In the Add Ref. Plane menu under Fitting Options set the Fitting Type to “Max. Bound” to create a plane surrounding all the selected entities.

e. Under Constraint Options select Axis Constraint and Use Specified Axis As Initial Guess. Then Select User Defined and choose the axis parallel to the long side of the reference plane you are creating. In the example in Fig. 5 this is the x-axis.[/wptabcontent]

[wptabtitle] CREATING A REFERENCE PLANE 4[/wptabtitle] [wptabcontent]

f. Click “OK” to create the Reference Plane.

Fig. 6: Click “OK” to accept the settings and create the Reference Plane.

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[wptabtitle] EXPAND REFERENCE PLANE IF NECESSARY[/wptabtitle] [wptabcontent]

3. (optional) If the resulting Reference Plane does not entirely enclose the entities, you likely need to expand it.

Fig. 7: The Reference Plane does not entirely enclose the entities.

a. In the Add Ref. Plane menu select the Convert option for defining a plane. Then select the Reference Plane you just created. Click “OK” and a larger plane will be defined.

Fig. 8: The final reference plane should fully enclose all the features you are including in the plan.[/wptabcontent]

[wptabtitle] CREATE ORTHOGONAL REFERENCE PLANE 1[/wptabtitle]

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4. (optional) Create Orthogonal Reference planes for further plans.

a. In the Add Ref. Plane menu select the Rotation option. Select the Plane you just created. This is the object which will be rotated. Select an entity, such as a polyline as the axis of rotation. Set the rotational Angle to 90 degrees. Click “OK” to create a new reference plane.

Hint: It may be useful to sketch a rectangle around the Reference Plane to create straight polylines for use as rotational axes.

Fig. 9: The Rotational method of creating a Reference Plane.

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[wptabtitle] CREATE ORTHOGONAL REFERENCE PLANE 2[/wptabtitle] [wptabcontent]

b. Enter Sketch mode by selecting “Sketch” from the main toolbar.

Fig. 10: The Sketch button on the Main menu.

c. In the Sketch menu select the Rectangle tool. Select the Reference Plane just created as the Base Plane.

d. Draw a Rectangle over the area where you want to create the next Reference Plane. Click “OK” to accept the rectangle.

Fig. 11: The Rectangle tool in the Sketch toolbar.

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[wptabtitle] CREATE ORTHOGONAL REFERENCE PLANE 3[/wptabtitle] [wptabcontent]

e. The rectangle should be nicely perpendicular to the first Reference Plane you created.

Fig. 12: The rectangle is perpendicular to the first Reference Plane.

f. Return to the Add Ref. Plane menu and select the Convert option. Select the Rectangle just created and click “OK” to create the Reference Plane.

Hint: Delete the intermediate planes after you have created the final Reference Planes.

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[wptabtitle] PROJECT 3D SKETCHES ONTO PLANES[/wptabtitle] [wptabcontent]

5. Once the Reference Planes are prepared you can project 3D sketches onto those planes.

a. From the Main Menu enter Sketch mode.

b. Set the Base Plane to the Reference Plane on which you wish to project features.

c. Select the Convert Entities button from the Sketch Menu.

Fig. 13: The Convert Entities button.

d. Select the entities you wish to project onto the reference plane by holding down the left mouse button and sweeping across them. Click “OK” to convert the entities from 3D to a 2D projection.

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[wptabtitle] PROJECT 3D SKETCHES – CONT.[/wptabtitle] [wptabcontent]

e. The features you selected should now appear as a 2D sketch listed in the Sketches menu on the left side of the screen.

Fig. 14: The 2D projection of the 3D vectors appears on the Reference Plane and in the Sketches list.
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[wptabtitle] EXPORT[/wptabtitle] [wptabcontent]

6. The 2D sketch can now be exported for annotation and manipulation in a CAD, GIS or Illustration program.

a. Right-click on the sketch in the Sketch list and select Export. Select the output format, .dxf is probably a good option.

Fig. 15: Export the Sketch.

b. Applying drawing conventions is not covered in the Rapidform tutorials. Be aware of regional (and even project to project!) variations in drawing conventions. We refer you to Approaches to Archaeological Illustration: A Handbook (Ed. Steiner, M., 2005, Council for British Archaeology and Association of Archaeological Illustrators and Surveyors).

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