Tutorial: View-dependent textures

5.7. Tutorial: View-dependent textures

Problem

Some objects have strong reflections or surface properties that vary significantly depending on the direction they are viewed from. Since 3DSOM Pro normally uses a single texture map to capture the appearance of the object this variation is not seen in the final model.

Solution

To improve the appearance of such objects, 3DSOM Pro can generate view-dependent texture so that the appearance of the object changes depending on the direction it is viewed from. This produces a result rather like QuickTime VR, but in real 3D as shown in Figure 5.7.1.

Figure 5.7.1. An object from two viewpoints with a normal texture (top) and a view-dependent texture (bottom).

These textures are generated by using the difference between the texture information from each of the original images. It requires a special display algorithm to do this, so the results can only be seen in the 3DSOM Pro viewer and when exported for use with the 3DSOM Java Viewer

Starting Point

Start with the completed model, including normal texture map. The view-dependent texture is not stored with the 3DSOM Project because of it's size, so you should be ready to export the finished model before closing the project.

Step 1

Open the Texture Wizard by clicking the Generate texture maps... button. Choose "Generate view dependent Texture maps" and then press Next > button.

Step 2

The total size of the resulting view-dependent texture depends on the number of images used to generate it — however to get a smooth appearance, you will need a large number of images. We recommend at least 16 images around the object and no more than 32. You can limit the number of images used at this stage — they will be chosen automatically using the image "Order" (see The Thumbnail Window section for details on changing this ordering).

TIP:	Only the "included" images will be used, so if you don't want a particular image to be used, you can mark it as "rejected" before opening the wizard.

Step 3

Press the Next > button to generate the view-dependent texture — this will take a short while. When it is completed, the View Dependent Textures button will be enabled showing the results.

To see the difference, rotate around the model and switch to normal textures and back again (see Figure 5.7.1). Look in particular at highlights or reflections on the object. While you rotate, the name of the closest image used to generate the view-dependent texture from your current viewpoint is displayed in the status bar (see Tour of the 3DSOM Pro user interface).

Step 4

If you want to keep the results, click the Export model... button and choose 3DSOM Java Viewer as the file type. Choose the Options... button and then ensure the "Export with view-dependent textures" is checked before exporting.