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Now onward to modeling. With ImageModeler you create models over the photographs added to the project. Moving on to the Modeling tab, you begin to model by selecting the correct primitive tool. In our case it will be the default tool: the cube. This is where the 3D locator points come in. You start by snapping to the first, then second (establish width), then third (establish depth), then forth points (establish height of building). (see image 006). As you can see from the attached image, the locator points are highlighted and a pale blue box is shown appearing around the one building. That pale blue box is the cube we just modeled in 3D space coordinated and calibrated to the images. You continue to model this way, utilizing various options for primitives and then editing the basics of these primitives to add more specificity to the models.
ImageModeler uses polygons and polymeshes (polygon objects) which are made up of vertices, edges, and faces. ImageModeler has a full compliment of modeling tools, enabling the creation of basic solids like cubes, planes, cylinders, disks, and spheres. There are a number of options for modeling control, such as cursor snapping filters, and constrained and unconstrained scaling. Additionally you can change the workplane from which you model off of. For complicated buildings you will no doubt need to add more markers/locators to allow precise control of snapping primitives to the correct areas in the photos.
ImageModeler allows you to view the model in wireframe mode (see image 007) or solids mode. As you can see from the image above, the background photo image gets turned off leaving just the model data visible. Moreover, you can turn off locator labels and you can determine how many windows to view at once (one, two or four box display) (see image 007). You can also mix and match visibility options in various windows, so for instance you have two windows with the background photo images showing behind the model data and two images without the photo data visible.
The texture extraction process enables you to obtain accurate frontal views of buildings. (see image 008) This is especially helpful when the building is relatively flat as the images can be imported into a CAD or illustration program to be drawn (traced) over. Now it is possible to obtain facades from a series of photos. The accuracy in this process hinges on good calibration of course, and it is necessary that you place into the locators two points for which you know their relative distances. Options in the texture extraction process enable you to do whole facades or individual faces.
What will likely happen in the case of buildings is you will end up with trees and other objects in the extracted textures in the foreground. ImageModeler allows you to extract these textures and import them into file formats suitable to image editing applications. ImageModeler lets you define a default image editor like Adobe Photoshop or similar program. Moreover, you can also ascribe a constant color to an object or face. This is useful in the case where you are unable to obtain photographic images of certain parts of a building (like a roof up high) or reentrant corners that are difficult or unreachable to photograph.
By default ImageModeler creates a RZI file -- a specialized ImageModeler XML file. However, with ImageModeler you can export in a variety of 2D and 3D formats such as: Alias/Wavefront's .obj, .ma; Autocad .dxf; Discreet's .ms; Macromedia Shockwave format, Lightwave 3D's format (.lws or .lwo), Softimage's .xsi, stereolithography STL and VRML 97. Depending on the format certain aspects come over like: cameras, markers, locators, 3D model data and textures. Textures come over as JPEG, PGN, TIFF, or PICT files.
Closing Comments and Recommendations
ImageModeler 3.5 offered solid and dependable performance on our Mac OS X Jaguar -based TiBook. In fact, the interface is tidy and so well laid out that using ImageModeler in the field directly with a digital camera is a worthwhile and doable proposition. The actual application installed without issue and never crashed. Modeling procedures and editing were activated quickly even on our aging equipment. While I can go on praising the interface and the application's logical workflow and layout, there are a few areas where this application can improve. Placing the world-coordinate system in the model is one clear example. I'd prefer to see this process made easier and explained more clearly. I would also like to see more advanced ruler and measurement tools and options and to access the units preferences via the Tool Properties palette.
If you are an architect or engineer looking to add a photogrammetry software application to your toolset we clearly recommend you consider ImageModeler as a top choice for this job. It can also be used to generate textured models of various objects from sculpture, industrial items like furniture, to items like packing boxes or display items. --- ANTHONY FRAUSTO-ROBLEDO, B.Arch., Editor
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