4.4. Tutorial: Optimising the surface geometry

Starting Point

Although not essential, it is usually better to have an initial surface generated from which the optimiser can start. You will also need to have all of your images masked accurately since the model will be optimised to fit these masks.

TIP:

You might want to use the Automask > Clean Mask menu item to clean up your masks - this will mask out any parts of each image that lie outside the current geometry. The "Constrain smoothed mesh to lie inside current geometry" option is equivalent but uses an internal copy of the masks. You can also create additional silhouette images and edit these if you want to capture particular features as described in the Adding synthetic silhouettes tutorial.

Note: Optimisation will discard any surface texture generated, but it will keep in place any clipping you have performed, so it is better to clip away the stand beforehand.

Step 1

Open the Surface Wizard by clicking the Generate surface... button and choose "Optimise Surface" then click the Next > button to go to the Surface Optimisation Page.

Step 2

If you have a smooth organically shaped object, choose "smooth approximation" to generate a smoothed mesh with few corners. Otherwise, either leave the default "reasonable accuracy" set or choose "exact fit" if you are confident that your masks are very accurate and you want the surface to exactly fit all the details on them.

If you have edited the masks to remove unwanted regions in just a few of the images (e.g. the stand or a subpart of the object) you will need to make sure the "Constrain smoothed mesh to lie inside current geometry" option is selected. This will prevent the non-edited masks affecting the geometry (and growing back the removed region).

TIP:	If you have a lot of images in your project or the silhouettes are particularly complex, optimisation can be slow, so it is a good idea to limit the number of images used at each optimisation step by setting the "Maximum number of images to use during optimisation" parameter.

Click the Next > button to start the optimisation process.

Step 3

After some initialisation, 3DSOM Pro will start to modify the surface, gradually smoothing it while ensuring the features on the silhouettes are captured.

During this process, you can see the current geometry and look around the model by rotating it in the View Model Window as usual. At this stage, the mesh will be displayed with the maximum number of triangles, and will only be reduced to your chosen decimation level when optimisation finishes.

Use the Pause button to halt the optimisation while you look at the results and then hit the Continue button to resume optimisation.

If you want to change the parameters, click the < Back button at any point to return to the previous step and edit them (for instance if the optimisation is proceeding very slowly you could reduce the number of images being used).

Step 4

You can either leave the optimisation to finish completely, or interrupt it when you are happy with the current surface. Click the Close button to leave the Surface Wizard keeping the current mesh, or click the Next > button to go on to fit a subdivision surface to the mesh (as described in the Compressing the geometry with subdivision surfaces tutorial).

When the wizard is closed, decimation will be initialised which may take a few seconds and the model will be displayed with your chosen number of triangles.