Original Article Date: May 28, 2010
This tutorial is based on 2004 article that was written for MicroStation XM. You can view that article here:
[[Make a DTM and drape an image MicroStation pre-V8i]]
Explore the file:
Download, open and explore 220_Points.dgn. In this 3D file you'll notice a model called Points that contains zero-length lines representing the peaks and valleys of a surface or ground terrain. Although these points are supplied with this tutorial, you can easily create your own if you have design software that can export DTM data to an XYZ text file. Once you have a text file, you can import the data into a design file by using the Import Coordinates tool from the XYZ Text toolbox.
Create the DTM:
To create a triangluated network of these points, follow these very easy steps:
If desired, create a new level - you might want to call it DTM for Digital Terrain Model.
Make this your active level, and set the active colour to 0.
Put all the points in a selection set, this can easily be done by using CTRL+A.
Navigate to the Create Meshes toolbox and choose Mesh From Points.
In the tool settings box, enable Expand to Rectangle and enter a datapoint to process.
To clearly see what the Expand to Rectangle button does, delete the resulting mesh element, and regenerate the triangles with that option turned off.
The difference is obvious:
Adjust the global lighting:
At this time the mesh is ready to be rendered 'as is' or you can drape an aerial over it which I'll explain in the following pages. In the meantime, let's just render the triangles to get a better idea of what the terrain looks like.
Before proceeding, ensure that you have generated the mesh without the bounding rectangle as explained above. You'll also want to turn off the elevation points since they are no longer needed.
In order to get a better rendering from this particular model, we'll first adjust the global lighting.
Choose Light Manager from the Lights toolbox.
Enable Ambient, Flashbulb and Solar and adjust the intensity as desired.
Render the surface:
Choose Smooth from the View Display Mode list as shown:
The brightness of the scene can be adjusted via the Adjust View Brightness control as shown:
Attach Image:
The next step in this tutorial is to drape an aerial photo over the resulting digital terrain model. However, before we do that, let's take a look at the aerial by simply attaching it via the Raster Manager.
From the Raster Manager, select File > Attach and select 220_Image.jpg. This image is georeferenced, so be sure to turn off Place Interactivly from the attach dialog.
The following graphic shows the image attached in the Top view. Note that the mesh has been turned off for clarity.
To remove the black collar around the image, right-click the image entry in the Raster Manager and select Transparency from the popup menu.
Enable the Transparent option and choose colour 0 to be 100% transparent.
Set the rendering mode of the isometric view to Wireframe by using the View Display Mode tool along the top of the view.
Image Draping:
The following blurb is snipped from MicroStation Help:
Image Draping is an extension to the MicroStation rendering feature. The draping function is based on a MicroStation rendering feature called Procedural Materials, which allows the application of a specific behavior to the raster image.
This image can be draped over a Digital Terrain Model (DTM) or any 3D object using the DCDRAPE.PAL Procedural Material. In the case of aerial photos or satellite images, the DTM should be used. By using the draping feature, Raster Manager seamlessly integrates any image in the rendering process in combination with 3D elements. It also supports lighting effects, shadows, fog effects, fly through, animations, etc.
Bentley Descartes is no longer required to drape rasters over digital elevation models.
The steps required to drape an image in MicroStation V8i are as follows and are described in detail below.
- Choose the Apply Material tool.
- Open the dcdrape.pal material palette.
- Assign the dcdrape material to the mesh.
- Enable the Draping option in the Raster Manager.
- Render the view to Smooth.
Let's do it!
Navigate to the Materials task and choose Apply Material.
From the Assign Material dialog, choose Open Palette and select dcdrape.pal.
From the Assign Material dialog, choose Assign by Level / Color.
In the isometric view, select the mesh element and accept with a datapoint to assign the material. If you repeat this step, notice that you'll get a message indicating that the material is already assigned.
In the Raster Manager, ensure that the Draping column is displayed. This can be verified by right-clicking on any column name and choosing Draping from the pop-up menu as shown below. Then ensure that the draping option for the attached image is enabled.
Finally, adjust the view display mode to Smooth and the image will be draped over the mesh.
To publish this model in a shareable format, print to a 3D PDF.
Enjoy!