by Dennis Collin
3ds Max has a wonderful ability of making lines renderable. Which is a very useful for big or complex site models or where you want to add little extra details like cables, wires and rails without having to pay a ‘penalty’ of a high face count. By using conventional commands like ‘Sweep’, ‘Extrude’ and ‘Loft’
The feature has been with Max since its first release but many users are unaware of its existence! Renderable splines can be enabled either on native Max drawn splines or imported geometry from imported CAD data. The renderable option normally will be available on the import dialogue box. Here we see an example of imported AutoCAD data.
Limitations for renderable splines are that the cross sectional shape needs to be circular or rectangular or square. However this is still useful for generic representation of wires, cables and rails etc. where excessive details of cross sectional profiles are not required. This facility makes it very useful for background ‘clutter’ to enhance the model, yet not add too much to the face count.
For example, to create a chain-link fence renderable splines could be used to make the major posts and an opacity map for the fence itself.
We have similar renderable spline options when we choose to link or reference an AutoCAD drawing instead. A linked drawing is useful if it is likely the source file will change and any resultant changes can be more easily updated to your Max model.
You do need to dig around in the Linked file presets however to access the different options. Select the relevant preset, choose modify and then the basic, advanced and spline rendering tabs should be apparent.
Spline Rendering settings Includes the size of ‘wires’, profile shapes, whether or not to have mapping coordinates, and real world map scale.
However sometimes when working with curves the lines can look pretty jagged which results in poor quality rendering results like the following image below;
Notice the jagged edge of the road kerb and grass. You may think that it’s just a case of setting the segments to a smooth curve but in fact that has already been done! From a distance it looks okay, but it can be annoying when going in for close ups!
The problem is to do with how Max interprets the line element. When working with curves this can be controlled by adjusting a value called ‘Interpolation steps’. This sets the number of segments a line exhibits between vertices. A higher value results in smoother curves lower values more ‘jagged’. Since we’re using renderable splines the increase in render times for higher steps is negligible. This setting on the native line object can be accessed in the Modify section of the command panel.
Max options Acad import options
If the view is changing, Ie. You may have a camera zooming in to an object for example, you could set the Step number to adaptive. This will ensure that Max will always present smooth curves and save having to set the step amount manually.
This altered setting makes a big difference to the final image shown below;
Notice the smoother curves on the kerb. Despite the better looking image the render time should be virtually the same as the ‘jagged kerb’ image. Whereas if we were to use Sweep or Loft, there would be a ‘face’ penality to pay. Therefore this facility is well worth considering should one’s scenes be slow in performance and slow to render. Like any job we have to do its all about getting it done on time!