Product Reviews

Many 3D artists derive pleasure from building models and wrestling with B-splines and subdivision surfaces, but software developers are turning to image-based modelling to extract 3D information from 2D images. ImageModeler from French company RealViz is one of the most comprehensive image-based 3D modelling packages on the market, and has just debuted on the Mac in its 3.5 version.

Image-based modelling starts, naturally enough, with images - photos to be precise. These can come from either digital cameras or scanned originals, although digital camera images are preferred. ImageModeler can also use images from Stitcher, RealViz's image-joining and perspective-correction application for large-format or panoramic images.

The interface is divided into six tabs: Load Images, Calibration, Measuring, Modelling, Texturing and Export. Once the images are loaded, you move automatically to the Calibration tab. This is where you add Locators - markers that pick out the same feature in each of the photographs. A nice feature of Locator positioning is the Magnifier: as soon as you press the mouse button, the area of the image under the mouse expands to 4x zoom, enabling Locators to be placed more easily and accurately. After about seven Locators have been placed, ImageModeler can automatically calibrate the Camera. After this, more Locators can be placed, but now a maximum of only two is needed for any given point, since ImageModeler can interpolate the third coordinate from the Camera calibration.

The next step is to move to the Measure tab, where the World coordinates are set - in other words, which way is 'up'. Since the model will ultimately need to be exported,

Model behaviour

ImageModeler provides the usual spectrum of primitives that can be mapped onto the Locators, and if your modelling needs are simple these will suffice, but generally ImageModeler's more complex tools will be needed. This is where you'll realise that you still need a degree of 3D modelling proficiency to work with ImageModeler, because the Locators don't themselves define vertices of an object - you'll have to pin object vertices to the Locators using the modelling tools.

There are options for adding and splitting faces, and for more organic objects there's the option to create a point cloud from which a polygon mesh can be derived. To do this you add individual Markers to a scene (a Marker is a Locator not used in the Calibration process). You can add as many as you want, but this can be time consuming. Luckily there's an Automatch feature that allows the coordinates of the Marker to be deduced from a single image.

The texture mapping process is automatic, and ImageModeler can seamlessly derive and UV map a texture around the polygons with no interaction from the user. Simply select the object, select the photos you want to use and run the extraction process.

Exporting textured objects is supported for Maya, Alias, OBJ, VRML, Shockwave and LightWave 6.0. The LightWave exporter, however, requires you to put the object, scene and texture files into their appropriate folders by hand. A solution to this is promised.

ImageModeler may not be ideal for novices, since it requires some modelling know-how. However, it produces convincing texture maps automatically and gives the serious user a lot of scope for editing and refining the models.