Using CAD Tools to Edit Your Mesh

There may be times when all you need is a nice water-tight mesh. Scan the part, run the Healing Wizard, maybe a Rewrap command, and presto! But what if you want to add a precise feature? Perhaps a few quarter inch holes for fastening locations or maybe you want to trim the part so that its an exact height. Well its a good thing you have Rapidform! In this post, I’ll show you how to use some of our CAD Tools on mesh bodies.

Overview

The main trick is that you need to remember that Rapidform is a history-based modeler. This means that if you want to use any surfaces or ref. geometry to edit your mesh, those features need to be above the mesh in the feature tree. I personally like making a copy of the mesh. This allows you to have an original copy in the file that you can always reference back to. So we just need to make the CAD entities we want to use to edit our mesh. Then we copy our mesh and use those entities on our copied mesh using the mesh tools.

The Scenario

In this post, we’ll use our Quick Start Guide sample model, the bottle. (C:\Program Files\INUS Technology\Rapidform\Sample\QuickStartGuide\Bottle.stl).

Our customer wants to take this scan of his and make a print out of the stl, but of course he wants some quick edits done. The printed bottle will eventually be made into a trophy on a stand, so they’ve requested that the height of the bottle be shortened by 0.315 inches. They’ve also requested that a clearance hole be modeled in so that they can tap and thread the bottle. It’ll be a 1/4-inch threaded post, so the hole needs to have a 7/32-inch diameter and be at least an inch deep.

Getting It Done

First we’ll create a plane that’s 0.315 inches above the bottom of the bottle. We’ll use this plane not only to shorten the height, but it will also serve as the sketch plane for our hole.

Conveniently the bottle scan is already aligned and its sitting on the Top plane. We can quickly generate a plane by using the CTRL key.

Thinking ahead, now we’ll use this plane for our 2D mesh sketch to make our clearance hole. The cross-section can referenced to make sure the hole is concentric (it happens to be centered around the origin), and the smart dimension tool will guarantee the size of the hole.

Using the sketch, we can extrude a surface (or a solid) that we’ll use to create the hole in the mesh. We need at least a 1-inch deep hole so we’ll extrude to about 1.15 inches.

Now that we have our tools ready, we’ll make a copy of the mesh using the copy and paste commands (Edit Menu).

In Mesh Mode (double-click on the Copied Mesh), we’ll be using the split command (Tools>Mesh Tools> Split). First we’ll split the mesh using Plane 1. Be sure to have “Cap Section Ends” checked, or if you prefer, you can use the fill hole command.

Then we’ll split the mesh again and use the surface body as the entity.

With a quick fill hole on the bottom, we have our mesh!

The result is a mesh file that has been modified with CAD precision, a unique feature found in your Rapidform Software.

Notes

A slightly different workflow can be used to generate the hole (or more complex shapes that one may encounter). Instead, you would convert the solid body into a mesh by making an empty mesh feature and using the “Convert Body” command. Then use the Mesh Boolean command (Tools>Scan Tools>Boolean) to cut (or merge or intersect) the shape.

We all know that the Rewrap command is useful for interpolating mesh data as well as smoothing noisy data. This post continues our look at the command with a third example. The first two examples can be found by visiting this post and this post.

Example #3

Generating a mesh for cross-sections: Generating cross-sections can be useful if you plan on creating lofts. Using 3d-sketch tools, you can smooth out and edit your cross-sections to create smoother loft surfaces.  Cross-sections can also be used to generate sweep paths, guide curves, and boundary-fit curves. What if your mesh is missing data? Or there are mesh features that you would like to omit from your final model? If each cross section was a 2d section we could use our sketch tools to fit geometry over the missing data. Or if they are 3d sketches, we manually could fill in the gaps with matched splines, and delete sections we don’t want. Of course, a much more elegant method would be to use the rewrap command.

In this example we have a Rapidform helmet. Most us application engineers in the company put these on to protect ourselves from the sales reps when the end of the fiscal year nears…

The scan itself is missing data and there a few features that we want to ignore during our modeling. With region groups, we can easily separate the areas of interests.

After deleting the unwanted data, or copying and pasting the regions of interest, we can run the rewrap command to simultaneously fill holes and defeature.

Now we can generate continuous cross-sections for Lofts…

for Boundary-Fit Surfaces…



or to help with Solid Modeling.

Final Thoughts
This concludes this 3-part series of Commands and Applications for the Rewrap command. Want to request the same for other commands? Have other questions or comments? Let us know in comments below!

We all know that the Rewrap command is useful for interpolating mesh data as well as smoothing noisy data. This post continues our look at the command with a second example. The first example can be found by visiting this post.


Example #2

Autosurfacing a mesh for CAD operations: If you are creating an auto-surface of a model, it is usually said that a majority of the editing must be done to the mesh since you are creating a verbatim model. But with XOR, you have the added ability to create a hybrid model, that is, performing CAD operations on a verbatim model to create a model that has both the accuracy from the scan as well as the design intent of a designed model.

In this example, we have an autosurface of a bottom of a bottle. What if the scan of the bottom of the bottle isn’t flat? Well then our autosurface of the bottom of the bottle may not be flat either.

Using the rewrap command, we can extend the mesh in a natural way, create our autosurfaced solid model, then create a perfectly flat surface.

We can also change the height of the bottle by using a different cutting plane!

More Examples…

We’ll be posting the final example of how this command can be applied soon! If you missed the first example, check it out here!.

We all know that the Rewrap command is useful for interpolating mesh data as well as smoothing noisy data. If you don’t, press The F1 Key.

We’ll take a look at a few examples of how we can apply this useful command.  Example #1 is below, keep an eye out for more examples which will be posted soon!

Example #1

Defeature complex features: Want to remove a feature from your scan and fill the space in naturally? If its as simple as a bump or lettering on a smooth area, use the Defeature command. But if the feature or its location is a bit more complex, the Rewrap command can help. Just delete the area and run Rewrap. Be sure to have “Extend Boundaries” checked!

More Examples…

We’ll be posting more examples of how this command can be applied soon!

© 2009 American Association for the Advancement of Science

Rapidform is used for scientific research every day, but rarely does it help with such an important discovery as this: ancient human footprints found in Kenya reveal that our ancestors had similar height, weight and walking patterns to us.  Matthew Bennett of Bournemouth University in the UK used a 3D scanner to capture these fossilized footprints and studied them with Rapidform.  You can read the news about this fascinating case or examine the paper published in Science, replete with various Rapidform-generated images.

Professor Bennett performed a variety of measurements of the footprints using Rapidform, and generated beautiful color maps showing the depth of each footprint in the prehistoric mud.  The cover of the Feb 27, 2009 issue of Science featured one of these color maps made in Rapidform. This important research made worldwide headlines because the findings represent the oldest evidence of modern-human foot anatomy.

This is another great example of how 3D scanning is being applied to all sorts of important work, from anthropology and medicine to manufacturing and new product development.

Source: Science Magazine [login required to read full article]

When you create a mesh, Mesh Buildup Wizard is typically used. If scan data consists of line type point clouds, then it is not easy to maintain the original shape of its boundaries while generating the mesh.

If you use the manual way of using 3D triangulation command in the Addins menu, you will get better result than the automatic way of using Mesh Buildup Wizard as shown in the image below.

Results from Mesh Buildup Wizard (image above)

Results from 3D triangulation in Add-ins (image above)

Method
1. When you apply triangulation with line type scan data which is already aligned by a scan device, accurately align scan sets again in the software. Select the Align button in the bottom pallet menu, or Click Tools > Scan Tools > Align in the menu.

Use the Global And Fine method with Apply Only Small Transform option as shown in the below image. This option considers that initial alignment is already done and accurately aligns scan shots removing gaps among scan shots by small transformation. And also if overlapped regions have planar shape, its alignment may slide along the planar area. This option prevents featureless scan shots from sliding during alignment.

2. Apply Addins > Combine command to make a single scan data.

3. Click the Addins > 3D Triangulate in the menu and check Assume Vertices Are Densely Placed Along A Direction option. Especially, when you try to triangulate line type point cloud, this option is appropriate for keeping edges or boundaries as it is as shown in the below image.

4. If necessary, execute the Enhance, Global Remesh and Fix Normal command in Mesh mode to get a mesh which is well optimized and featured.

The application has no command to convert a mesh to poly-vertices.

So, you may easily think that you need to import the existing mesh data using the “Point Only” option in the Import dialog box or export the existing mesh data by point type file format and import it again.

Through this technical tip, you will understand how to copy poly-vertices from a mesh without any data transporting process.

Method1 – Copy Poly-Vertices from Whole Meshsuch
First of all, Copy a mesh (Ctrl+C) in the Default mode.

Enter the Point Cloud mode (Insert > Point Cloud) and paste it (Ctrl+V). The copied mesh will automatically convert its property to a point cloud as shown in the image below.

Method2 – Copy Poly-Vertices from Partial Mesh
Double click the mesh to enter the Mesh mode.

Select a partial region from the mesh or select a region of interest by dragging and copy it (Ctrl + C) and exit the Mesh mode.

Now enter the Point Cloud mode and paste it (Ctrl + V) which is registered on the clip-board. You can get poly-vertices as shown in the below image.

When you create a mesh, you typically use the Mesh Buildup Wizard. If scan data is constituted by line-type point clouds, however, boundaries are not easy to maintain in their original shape while you generate the mesh.

If you manually triangulate using the 3D Triangulation command in the Addins menu, you will get better a result than the automatic Mesh Buildup Wizard method, as shown in the image below.

Method:
1. Before you apply triangulation on line-type scan data which is already aligned by a scan device, we recommend that you accurately align the scan sets again in the software. Select the Align button in the bottom pallet menu, or Click Tools > Scan Tools > Align in the menu.

Use the Global And Fine method with the “Apply Only Small Transform” option as shown in the below image. This option considers that the initial alignment is already done and accurately aligns scan shots, removing gaps among scan shots via small transformations. Plus, if overlapped regions have a planar shape, the alignment may slide along the planar area. This option prevents such featureless scan shots from sliding during alignment.

2. Apply the Addins > Combine command to make a single scan data set.

3. Click Add-ins > 3D Triangulate in the menu and check the “Assume Vertices Are Densely Placed Along A Direction” option. Especially, when you try to triangulate line type point cloud, this option is appropriate for keeping edges or boundaries as shown in the below image.

4. If necessary, execute the Enhance, Global Remesh and Fix Normal commands in Mesh mode to get a mesh which is well optimized and featured.

This technical tip will help you understand how to create a high quality fitting surface.

Step 1: Mesh Optimization

To get a high quality fitting surface, you will first need to prepare the mesh through some optimization processes. If the size of the poly-faces is regular and the resolution of the mesh is high enough, you will be able to fit a more ideal surface.

How to optimize a mesh to get a high quality fitting surface:

Note: XOR provides you with several methods to optimize a mesh from its current state, such as Healing Wizard, Fill Hole, Smooth, Enhance Shape, Optimize Mesh, etc.

If some abnormal faces and various defects exist in the mesh, you can easily find and clean them with the Healing Wizard command.
If some holes exist in the mesh, you can easily close them with the Fill Holes command.
You can also enhance the quality of the mesh using the Enhance Shape and Optimize Mesh commands.

1. Double-click the mesh, or click on the “Mesh” mode button in the Tool Palette, to enter Mesh Mode.

2. Click the “Healing Wizard” button or click Tools > Mesh Tools > Healing Wizard.

3. You can check which kinds of defects are in the mesh and how many there are, as shown in the image below.

4. Click the OK button

Note: The Healing Wizard automatically heals various defects in the mesh.

Folded Poly-Faces – If checked, folded poly-faces will be deleted.
Dangling Poly-Faces – If checked, you will remove any 2 or 3-sided open poly-faces.

Small Clusters – If checked, you can set a value for the Maximum Face Count In A Cluster; then all clusters (a group of connected poly-faces) that have less than the specified number of poly-faces will be removed.

Small Poly-Faces – If this is checked, you can input a value in the “Area Is Smaller Than” box, and poly-faces whose areas are smaller than this value will be removed.

Non-Manifold Poly-Faces – If checked, non-manifold faces and redundant poly-faces will be removed.
Crossing Poly-Faces – If checked, all the crossing faces will be removed. There are three methods: The Smooth method smoothly regenerates poly-faces around the crossing poly-faces. The Merge Poly-Vertices method merges poly-vertices around the crossing poly-faces. The Delete And Fill Hole method removes poly-faces around the crossing poly-faces and fills in the hole(s) there.

Small Tunnels – “Small tunnels” means that the poly-faces’ shape is constructed as a tunnel or handle. If Small Tunnels is checked, you can adjust the Poly-Face Count In Tunnel box. Then the tunnel faces whose number to the tunnel direction is shorter than this value, will be removed.

5. Click the “Defeature” button or click Tools > Mesh Tools > Defeature.

6. Select the Flat option as the “Method” and select a region to remove features and fill faces in that region, as shown in the image below.

7. Click the OK button.

Note: “Defeature” removes the selected poly-faces and fills in the space based on adjacent poly-face information.
If you want to re-form the feature after you generate whole surface body, you have to prepare a feature profile beforehand.
Another way to do this is, before Defeature operates, to copy the original feature into its own new mesh using Copy (Ctrl + C) and Paste (Ctrl + V). You will then be able to work with it later.

Note: You can fill faces in the missing area using “Fill Holes” or clicking Tools > Mesh Tools > Fill Holes.

8. Click the “Optimize Mesh” button, or click Tools > Mesh Tools > Optimize Mesh.

9. Select the “High Quality Mesh Conversion” option as the Method, and adjust the options as shown in the image below.

10. Click the OK button.

11. Check the result.

Step 2: Create Boundary Curves

Secondly, you can prepare boundary curves to create a fitting surface on the mesh. If the number of curve boundaries is 4 and the shape is a regular rectangular feature, you will get a better fitting surface.
Otherwise, a fitting surface will be twisted and have some self-intersection(s).

How to organize boundary curves to get a fitting surface:

Create 3D Mesh Sketch
• Create boundary curves which can keep the equilibrium of forces
• If the number of boundary curves is 4 and its shape is a regular rectangular feature, you will get abetter fitting surface, as shown in the image below.

• Even though you can keep that the number of boundary curves at 4, if its shape becomes suddenly narrow or twisted as shown in the image below, twisted and self-intersected faces could be created when the surface is generated.

Match Boundary Curves
• If possible, avoid “T-Junction” matching when you create curve networks
• If not, organize “T-Junction” matching so that the curve networks can keep the equilibrium of forces as shown in the image below.

• Other than the 4 sides of the curve boundary, others will create a trimmed fitting surface.
• If trimmed surfaces are neighbored with the same matching boundary, those will not be matched.
• Organize the curve network so that the surface matching conditions can be applied.

For Example:
Untrimmed Surface – Untrimmed Surface
Untrimmed Surface – Trimmed Surface – Trimmed Surface
Untrimmed Surface – T-junction matching – Untrimmed Surface

• If possible, setup the same number of control points in the each matching boundary of the surface patches to improve surface matching continuity.
• If possible, setup the boundary curves using appropriate control points to apply the fitting operation.

Create Curve Network
• If the shape is going sharp or dull, you can manage the number of curve boundaries according to the shape, as shown in the image below.

• If a fitting curve is not correctly put on the mesh, an accurate fitting surface cannot be created.
• In that case, increase the number of control points on the curve using the “rebuild” option

Step 3: Create a Boundary Fit Surface

Finally, you can create a fitting surface using the pre-defined boundary curves.
However, even if the curve networks are well organized on the mesh, the fit surface will be created a bit differently, according to the defined fitting options.

How to use options to get a high quality fitting surface:

Boundary Fit operation has been separated into 2 stages:
• In the first stage, you can set Mesh Curves, Curve Loops, and Loop options.
• In the second stage, you can define sharp edges to keep the sharpness at the boundary, as well as the number of control points in the surface to be created. This is shown in the image below.

1st Stage (Setup Curve Loops):
• Allow Hole (Boundary) – If this option is turned on, the surface will be created even though a hole exists inside the boundary of the curve, as shown in the image below.

• Allowable Convex Ratio – In the case that some feature(s) exist inside the loop, this option allows you to create a surface using a Convex Ratio.

2nd Stage (Adjust Fitting Options):
• Set Resolution – you can adjust the resolution of a surface patch via “Number of Control Points” or “Allowable Deviation.”
  • If possible, set the same number of control points along the U and V directions, as you can get a better surface body that way.
  • Using “Set Manually,” you can easily set the control points along the U and V directions of a surface patch, as shown in the image below.

• Set Sharp Edge – Use this option if a sharp area exists in a mesh, or if you need to keep the sharp feature on a surface body.
  A position matching operation will be applied to the boundary only.
  In this way, you can preserve the sharp edge in the surface body you’re creating and modify it whenever you want.

• Resample – If this option is turned on, the fitting area will be regularly simplified and a smoother surface will be generated.
  However, you can decide whether you turn the option on or not according to your particular application.
  If you want to generate a surface body as close as possible to the mesh (“as is”), even if the resulting shape would have positive or negative complex features like under-cut areas, turn off this option.

When you import scan data, the data will be loading in the software, and a new Mesh Feature will be added in the Feature Tree. Sometimes, you can have additional items created after the Mesh Feature, but you will not be able to immediately be able to trim the mesh using these items. This is because parametric CAD systems have a history, meaning that it not only records what you do, but when you did them, and what the current state of the model was at that time. When we Rollback to edit the model, we are going back in time. Any items that did not exist at that time will not be available. We have three possible solutions to this situation, as follows:

Preparation
1. Click the (Import) button, Click Insert > Import to open the Import dialog box.
2. Select all files.

3. You can see an unedited mesh data as shown in the image below.

1. Using Ref.Plane

First at all, when you create a Ref. plane, the plane feature is recorded under the mesh feature. In this case, you will not be able to select of use the Ref. plane. We can, however, chage the order of the events in our history. By moving the plane to occur before the mesh, we will the be able to use it while editing our mesh feature.

You must move the Plane 1 up before the mesh feature, as shown in the image below.

Double click the Mesh Feature in the Feature Tree or click the (Mesh) button. You will enter the Mesh mode, and then you can edit the mesh by using the Ref. plane.
You can see the Ref. Plane in the Mesh mode as shown in the below image.

Click the (Split) button, or click Tools > Mesh Tools >Split in the menu.

Check By Entity as Method and select Plane1 as the Tool Entity. If you want a closed mesh, you can check the Cap Section Ends option. Click the (Next) button.

Select the remaining region and click the (OK) button.
Shown below is a split mesh.

2. Using a 3D Sketch

This method is to use the 3D Mesh Sketch. First at all, you must sketch a line by using the spline command, and then copy and to move it.

Click the (3D Mesh Sketch) button. Click the (Spline) button, or click Tools > 3D Sketch Entities > Spline in the menu.

Sketch the spline on the mesh as shown in the image below.

Click the (OK) button. You can see 3D Sketch 1 Feature located under the Mesh Trim Feature. In this case, you cannot edit the mesh with the 3D Sketch.

Select 3D Sketch 1 in the Feature Tree and copy it using Ctrl + C on the keyboard.

Click the Ok button.

To paste the Copied Sketch (Ctrl + V)

Select Copied Sketch and move it up before the mesh feature as shown in the image below.

Double Click the mesh and enter the Mesh mode.

Click the (Trim) button and check By Curve as the Method. Select the previously created spline as the Curves. Click the (Next) button.

Select the Remaining region and Click the (OK) button.

Shown below is a Trimmed mesh

3. Moving the mesh

This method is to use the copy & paste command and is very similar the previous method.

Click the (3D Mesh Sketch) button. Click the (Spline) button, or click Tools > 3D Sketch Entities > Spline in the menu. Sketch the spline on the mesh as shown in the image below. Click the (3D Mesh Sketch) button again to escape this mode.

Select the mesh in the Feature Tree and copy it using Ctrl+C on the keyboard.
Click the OK button.

Paste the Copied Sketch (Ctrl +V) and it is automatically placed at the end of the Feature Tree as shown in the image below.

Note

If the mesh is not placed in the appropriate place, under the 3D Sketch; you must click-and-drag to move the mesh feature below the sketch feature desired.

Double click the Copied Mesh to enter the mesh edit mode.

Click the (Trim) button and check By Curve as the Method. Select the created spline as the Curves. Click the (Next) button.

Select the remaining region and Click the (OK) button.

Shown below is a trimmed mesh.