3D Site Modeling in Context
Modeling Buildings from Photographs
When trying to understand a site and its context, it is often useful to represent a building with recognizable form. Such a building may be a landmark that is visible form our site, or a beloved neighborhood building that we want to preserve in our scheme. If we are lucky we may find such a building in the Google 3D warehouse. Otherwise we may need to model the building from observations made with our camera. This exploration of building modeling will introduce the application of textures to faces, and the use of components and instances and the copy array technique. Along the way, we will take a look at the very cool photogrammetric application of sketchup that allows us to model the geometry of buildings from photographs.
Download the Sample Data
About James Hall
James Hall is home to several of the social sciences programs at Harvard. It is a convenient building to practice some simple sketchup moves because it is more or less rectangular with a few interesting deviations. It also includes several butteresses that are identical and spaced evenly across the face of the building. And it is visible from many classrooms at the Harvard GSD.
Playing With Textures
THe first thing we will do is begin to model James Hall from its image in Google Earth and a photograp that we took from the street. This will let us play with the straightforward placement of an image texture onto a building. THis is a bit tricky since our google earth photo is not a 'true ortho' we can expect the geometry to be accurate only where the building touches the ground. SInce James Hall is so tall, its top is offset subvstantially, which obscures most of the footprint. This is typical. We will do the best we can.
- Open the model Google Ground, which has simply been captured from Google Earth.
- Trace a rectangle, beginning with the one straight-edge of the building
that we can see. Make sure to use your pink inferences to keep your rectangle square.
Use the push-pull tool to pull up the building until it looks like the right prop0rtion
- Use File Import to import the image, james_perspective_low-res.jpg> as a Texture.
- Place the bottom corner of the textrure and stretch it up so that it covers your building face.
- Now right-click and say Texture->Position
- Use Floating Pins to stretch the texture onto the building.
Using The Photomatch Tool
Fitting images to your sketchup geometry is useful as we just saw. Now you will see how useful it can be to go the other way. Sketchu's photomatch capability uses the perspective properties of a photograph to create a scene that is set up with your point of view being more or less precisely where the camera is. YOu must help it by providing a photograph that has not been cropped (because a substantial ampount of information about the geometry of the scene is derived from the assumption that the center of the photo is orthogonal to the center of the scene.) YOu also assit the process by aligning several guides along paralell lines on your building, and placing the origin of your axes on a place where you can inspect the alignment of the axes along some right-angle portion of your building. This scene orientation is saved in a special scene tab. When you return to this view, the inferences that assit you in making things paralell serve to let you create a 3d model using your photograph as a guide.
If you want to see the whole process, you may want to take a look a the PhotoMatch Technique Videos Parts 1 and 2 from the Sketchup Video Tutorials Collection.