Considering R13 has been rewritten from the ground up, I was happy to find myself comfortable with it from the beginning. I loaded my old AutoLISP command shortcuts, and was immediately at home. Autodesk has taken pains to ease us into this next stage of AutoCAD. I'm slowly increasing my usage of the customizable icon interface, and expect a new operating style to develop naturally.

3-D modeling. Since much of my current work involves conceptual designs using AME, I started with the 3-D modeler. Operations seemed familiar even though the internal operation of the ACIS kernel is totally new. R13's 3-D editor uses commands similar or identical to those of AME, and new features are easy to learn. The real difference comes with the NURBS-based definition of curves and true ellipses. Now, complex shapes are defined compactly and accurately.

I was particularly pleased with the successful construction of a hydrodynamic shape that I had been unable to generate with AME. R13 easily filleted edges defined by elliptical and other non-circular, curved intersections.

Since R13 doesn't retain solid primitives which have been used for booleans, it can't support an equivalent of the AME SOLCHP command. Modifying completed solid features can be performed only through additional construction. In the long run, Designer will more than fill this loss. But for now, some discrete SAVEs and use of AutoCAD's still exceptionally robust UNDO are satisfactory.

2-D drafting. The 2-D drafting improvements in R13 are extensive. Associative boundary hatching is intuitive and efficient, and hatch edits have eliminated erasing and re-hatching. Trimming is a breeze. Intelligence has been added to dramatically reduce the number of steps needed for complex trims. I found these editing improvements, along with projected and implied intersections for both trim and extend and relaxed UCS restrictions, among the most productive in R13.

Dimensioning offers a wealth of new and improved features. All dimensions are associated with easily edited, expanded styles; and style overrides permit custom formatting at the single-dimension level. I found nearly any visual effect was possible.

The new linear dimensioning command permits rapid construction of both vertical and horizontal dimensions without additional commands. Additions such as multi-line text entry, expanded baseline and continuous dimensioning, and improved drafting standards support offer everything I need at present.

3-D to 2-D transition. Although the manuals offer no equivalent of AME's SOLPROF command, proper setting of the DISPSILH silhouette control variable produced a reasonable facsimile-adequate enough to provide clear, facet-free isometric views.

However, I would like to see improvement in this area. I think a projection command should be added to provide flat, explodable, clean views suitable for efficient dimensioning.

AutoCAD's built-in rendering capability continues to grow, with materials, more lighting options, and Phong shading producing a significant improvement in realism. I found rendering fast enough to use frequently, now competing with HIDE and SHADE as an interactive tool. File export of rendered images was invaluable for image editing and for compilation into other Windows documents. I used the direct .3ds file export to 3D Studio and was pleased to bypass the .dxf file export/import methods used earlier. I had to make some surface normal adjustments within 3-D Studio, but found the overall process very satisfactory.

All-in-all, R13 met, and in many cases exceeded, my expectations. I'm particularly pleased with the new ACIS capability, and am impressed with the general stability and robustness of code which has been so extensively revised.