Project01_Scultping Terrain:  Scanning and Slicing Procedures

Overview:
Clay Modeling -> 3D Scanning -> Image Slicing (Contours) -> AutoCAD (Refinement)

Clay Modeling:
Each student will work towards a design proposal that is clearly represented in a clay model. The design must be legible and artful in its approach. Simplicity of concept and landform will help you meet both of these goals. The final model must be to scale both horizontally and vertically and free of smudges, scars, gaps, or any other deformity. Any clay models not meeting these criteria must be revised and resubmitted prior to proceeding to the scanning process.

3D Scanning of your Design Proposal:
The scanning process will use instructor provided 3D scanning technology. This particular is the Occipital Structure Scanner that attaches to the Apple iPad. The resolution and accuracy for this device is enough for us to get a quality scan of the clay surface. Higher-end technology can offer a much more precise scan, more suitable for this type of process.

Each student will be provided with this technology and, under the supervision of the instructor, will scan their clay model to obtain a digital file of their physical model.
With the Structure Sensor mounted to the iPad, open the Occipital Scanner Application and follow the on-screen commands for scanning.

Upon completion of scanning you model, each student will email the digital file to themselves from the iPad. The default filetype is an “object” file or .obj and it is suitable for our purposes in Rhino.

Overview of Rhino:
There are four screens in Rhino, each showing different viewpoints: Top-Left is Plan View (called TOP), Top-Right is Perspective (called PERSPECTIVE), Bottom-Left is Elevation View from the Front (called FRONT), and Bottom-Right is Elevation View from the Right (called RIGHT).

To activate a window, click in that particular window. You zoom back and forth by simply rolling the wheel on your mouse. In Top, Front, or Right view, you can pan by holding right+click and dragging our mouse. Right+click and dragging your mouse will orbit in the perspective view. Commands like Move, Rotate, etc. can be accessed by typing the desired command which will appear in the command line at the bottom of the interface.

Converting the Scan to Contours:

The procedures listed in this tutorial are specific to the Macintosh version of this program and may appear slightly different in a windows based version of the program

1. Go to FILE and select OPEN. Find the .obj file on your computer and open the image in Rhino. Select OK to import the image using the Default settings in the dialog box.

2. ROTATE the image to orient the 3D image correctly. This process is done easiest if performed in a side view of the 3d model. This is typically the RIGHT display window in the bottom right hand corner. To rotate, simply type “ROTATE” into the command line and press enter. Follow the prompts for the rotate tool.

a. Select the model to rotate and press ENTER.

b. The first LEFT CLICK should be near the center of the model. This sets the axis that the rotation will occur on. Before the second click, you will hold SHIFT to lock the rotation to 90° increments. With SHIFT pressed down, CLICK ONCE in the direction the model is facing and CLICK AGAIN in the direction you wish to rotate the model. For our purposes, the first click is typically straight up and the second click and to the right.

c. Verify that the model is rotated in the viewport and proceed to the next step.

Step A through C are specific to using a scan from the occipital structure scanner and will not apply to all scans that are imported into Rhino. The overarching goal of these three steps is to rotate the model so that it is oriented correctly. This means that “up” for the terrain is “up” in the model. Depending on the import, it could already be correctly oriented or may require multiple rotations and tweaking. Once it is correct, proceed to step 3 of this section.

3. The digital model will be close to the same scale as the physical model that was constructed. You will need to SCALE the model to the actual size of the design proposal. For example, if you have modeled your terrain at 1”=10’ (also known as 1”=120”), you will need to scale the digital model by 120. The goal is for 1” in your digital model to equate to 1” on the actual site.

a. In Rhino, type UNITS into the command line and click ENTER. Ensure that the model space is set in FEET. Click OK.

b. Outside of Rhino, Measure a large and easy to determine distance on project site. This can be done in AutoCAD and the distance should represent the actual distance on the site. This measurement will be in feet and consider this measurement “A” for actual.

c. In Rhino, type DISTANCE into the command line and click ENTER. Click on the model and measure the digital model distance of the same measurement from the previous step. Write down this measurement (which will be in feet) and consider this measurement “D” for digital. Note that the digital distance is drastically smaller than the actual onsite distance.

d. It will be essential to determine the scale factor using the two measures made in the previous steps. To determine the scale factor, you must divide the actual distance “A” by the digital distance “D” to determine the SCALE FACTOR.

e. Use the SCALE command to scale the model to the appropriate distance. Type “SCALE” and press Enter. Select the object (your model) to scale by clicking on the object and press Enter. In the FRONT (Bottom-left) Window, set the origin point somewhere slightly below the image. Next you will type in the SCALE FACTOR and press ENTER to scale up the model to the correct scale.

f. After scaling the model, the model will be too large for the viewport. You can ZOOM to the EXTENT of the model by typing “ZE” in the command line and hitting Enter.

g. Use the DISTANCE tool to make sure the model is now scaled correctly. If correct, move to the next step. Otherwise, start again with part B of the current step.

4. To create contours on the model, type “CONTOUR” and press Enter. Next select the object to be contoured. In this case it is your 3D Model. Set the “Contour Plane Base Point” somewhere slightly below the 3D model by clicking below the model. Then drag the line to above the model, while holding the SHIFT key to ensure 90° angles.

a. The distance between the contours should be 1 unit. If this is not already the established interval, set this by typing “1” and pressing ENTER. If it is already the interval, press ENTER to make the contours.

5. After creating the contours, click in the “TOP” Window. Next select the underlying wire mesh upon which the contours were laid and delete it. Then select the “FRONT” Window and use the cursor to select the lower portion of the 3D model that is unimportant and unneeded. This unneeded portion will likely be the table that was picked up in the scanning process. You only need the upper portion that has the contours you are interested in.

6. Save the 3D image with contours: File -> Save As -> Use the drop-down menu to save the file as a .DWG file.

 

Integrate into AutoCAD:
The primary advantage of scanning your physical model and creating contours in Rhino, is that you import these contours directly into AutoCAD. It’s important to note, however, that the contours are only as precise as the clay model itself and the resolution of the 3D scanner. For this reason, you will consider these contours as a GRADING SKETCH to help you visualize how the contours will work across the site and tie into existing contours.

The first step is to insert these contours into your base plan. Follow the procedure below to integrate the two files.

1. Open .dwg file exported from Rhino in AutoCAD. Click “yes” to continue opening the file.

2. Create a NEW LAYER and name that layer “Grading_Sketch”. Select all of the linework in the drawing (Crtl+A) and place it on this new layer. Select all of the linework on that layer again and go to EDIT>COPY in your menubar. If the menubar is not visible, type MENUBAR and hit enter. Then type 1 and hit enter.

3. Open your base plan from part 1 of this assignment. Make sure you are in model space and zoom extents (ZE + enter). Go to EDIT>PASTE AS BLOCK to paste the “Grading Sketch” into the new drawing.

At this point, you will need to align your contour “Grading Sketch” with your base plan. The contours may not align exactly but this will give you the bones of your conceptual grading plan. The geometry in the grading sketch will be too coarse for you to actually use in your final grading plan so it will be necessary to redraw your grading plan. Contour lines should be evenly spaced to match slope of the design proposal and spot elevations should be included throughout.

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