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By VRgrafix

IGES import - Architectural modelling - Part 1

Advanced tutorial

With this tutorial we will tackle a real-world example of modeling a standard house, plus a proposed extension from architectural CAD files. This method of modelling is not only very fast but accurate - two very important factors in architecture.

With the tutorial we will assume that you have created the basic shapes in your CAD application and have exported them as IGES files - ready for importing into Realsoft 3D. These IGES files along with the relevant CAD files and Realsoft project files can be downloaded in this zip file. These files were exported from Microstation - one of the more popular CAD packages. Several textures are also included.


Part 1 - Importing IGES files
Part 2 - Garden Modelling
Part 3 - Texturing model
IGES techniques - Preparing IGES files and Tips

Part 1 - Importing IGES files

For this exercise, we have created the IGES files for you. To import these files into RS3D we simply LOAD them in using the standard loader in RS3D. (CTRL+L) Browse to the IGESfiles directory and select "House.igs". The load requester changes to show various options before importing the file. Check / uncheck the various options to read:

iges 1 iges 2
IGES import GUI options

These settings leave our object in the same physical location as the CAD file, groups the objects by color, and imports all lines as polyhedrons. Select "LOAD". Drag the ROOT directory icon to the view to view all objects. (We need to do this to set clipping planes and zoom all objects - CAD files are generally large, and simply zooming out will not show the objects)

Depending on your view orientation, you may have to rotate the view to see the objects. CAD files generally use "Z" as the up axis, RS3D uses "Y". Hence this particular file has imported the house in "sideways". We will leave the file like this until we have finished all of our importing - otherwise they will not be imported into their correct location.


Import the following 2 IGES files without changing any loader settings: Garden.igs and Pergola.igs (Note: Turn off "Replace" checkbox on successive imports - we do not want to overwrite the files we have imported - only append to them.)


The last IGES file to import is the Roof - but we want the roof to be imported as an SDS object so we can build the faces. To do this, simply change the polyline import option to SDS and load file: Roof.igs. We now have all the information loaded to finish our house. But these objects currently have no depth. Lets organize the file first by renaming our directories into something meaningful. Rename the directories as follows:

select1 --> select2 --> select3

You can further organize the levels by dropping the garden levels to a level, as well as the house and pergola. Lets focus on the house level to start with - so select the pergola and garden levels and make them wireframe invisible.

Our whole scene is 90 degrees in the wrong direction - so for the sake of simplicity lets rotate the whole scene 90 to the left. Take a side view - select the "Root" level and zoom out until you can see the object handle. Hold down the SHIFT key and rotate the object on the red rotate handle until the whole scene is vertical.

We now need to assign a depth to all the polyhedrons we have created. To do this we need to multi-select the objects themselves (not the levels). Start with the 'Windows'. Multiselect all the objects in the windows directory and go to the "Spec" tab under object properties. Type in "1500" into the depth field. Tumble the view to see the result. Note that the window shapes have been extruded. However, we wanted the extrude to go downward, not up as they have done. This is a common problem when importing IGES files as each object can have its up or down normal flipped. To change it in the other direction, simply put a negative in front of the 1500 value. (-1500). This flips the objects over, but the value remains 1500. The windows are at the common height of 2100 - hence we can change each size individually and the top sill will remain at the correct location.


Next, go to the 'walls' level. We have two objects in here - one is lower that the other. This is the outer brick wall. Select the low wall and give it a depth of 3600. (You may have to change its direction by adding "-" to the front of the depth value). It should now be facing upward towards the roof. Rename this object "outer wall".

The next object can be extruded 2800 up - rename this "inside wall cut" We are going to use this object and the windows level to cut out the necessary holes from our building. First move our "inside wall cut" object into the windows level. Now select the "outer wall" object by itself, then shift select the "windows" level. Boolean Cut the windows from the outer wall. (Boolean AND NOT command - SHIFT+N) Move the resultant Boolean level back under our "House" level.

Note that the Boolean cuts use the object colors to derive the cut color of each surface (this is an option). We can use this to our advantage to keep the interior walls white for example. Change the color attribute on our "Inside wall" object to white and try rendering the view. (You may need to make the roof level raytrace invisible to see inside).

Continue on with the house level and change the following values:

Slabs - depth value of 100 to all objects
Interior walls - depth of 2400 up.


And finally for the house, we must create our roof. Lets start by making all other levels wire invisible so all we can see are our two' roof' levels. Select the subdivision object under the 'Roof' level and 'Edit' the object. Select the "Create Faces" tool from the toolbar. Holding the SHIFT key - place two points on the existing object. Then hold down the comma "," key and drag select a box around one of the ridge points on our roof ridge curve. Then the last point on the ridge curve again with the comma key. This has now created a face on our SDS object - using the construction lines we created in CAD for the roof as a guide. Finish off the rest of the roof in the same manner by snapping to the SDS object using SHIFT and snapping to any other geometry by holding the comma key. (You may need to turn off auto accept 4 faces as two faces of our object only need 3 points).

To add a gutter line to the roof, go to face edit mode, then select the large face underneath the roof and extrude the face 150mm.

You can now delete our construction curves by deleting the "Roof ridge" level.

Our basic house form is complete.


To finish modeling the garden and pergola - go to Part 2 - Garden modelling

To texture up the house - go to Part 3 - Texturing


Page updated on Tuesday, 25 February, 2003 . For feedback / model submissions or articles - please email us.
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