3DPlants.com - Tutorial #1 - Optimizing Imported 3D Models

Many 3D modeling and rendering programs include an option for "smoothing" 3D objects, either as an import/save option or as an editing command function. Smoothing is probably the most effective way of improving the look of organic 3D models, or any mesh object that has a lot of curves or rounded surfaces. Basically, what it does is to remove the sharp angles and corners that are formed where the edges of polygonal faces meet along the surface of an object. Some programs allow for varying degrees of smoothing based on a percentage, or constrained to a specific threshold angle. Over-smoothing can result in undesirable effects. Trial and error is the best way to determine the amount of smoothing to use on any given object. Some file formats, such as 3DS and OBJ, include the ability to embed smoothing data into the file. Below are several images showing the effects of varying degrees of smoothing applied to an object in Bryce 3D.


No Smoothing		Smoothing		Over Smoothing

Due to differences in the way that certain programs interpret 3D file data, sometimes the polygon faces are accidentally "reversed" on import, causing the visible surfaces to face inward, and thus making the outward surface appear invisible. Many 3D programs have the capability to automatically examine and fix polygon faces or "normals" by aligning them all in the same orientation. Other programs allow for manual reversal of individually selected polygon faces that are not oriented correctly. Below is an example of how an imported 3D object might appear before and after reversing errors in polygon face orientation.

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Before reversing polygon normals		After reversing polygon normals

Many 3D models are made up of a group of objects that can be selected and modified individually. Check the import options of the 3D program that you are using and make sure that imported objects are not merged into a single mesh object. Some model formats, like obj and 3ds, can also contain materials, regions, or layers which define certain areas of the model, usually for the purpose of applying texture maps. If you plan to apply a mapped texture to the imported model, make sure your 3D program preserves materials or mapping regions on import.

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DXF import options - Corel Dream 3D		3DS import options - 3DWin

Some 3D programs have the ability to perform node or face reduction on polygon mesh objects. This can be an effective way of reducing file sizes and speeding up render times. Unfortunately, this also tends to reduce the amount of detail and sometimes causes unwanted distortion of the object. This operation is best performed on objects that have an excess number of polygons to begin with, or distant objects for which the loss of detail is not as noticeable. Below is an example of a mesh object with varying degrees of polygonal face reduction.

	..		..
10608 Polygons		4000 Polygons		2000 Polygons