CompuServe Messages

<<…just saw that you use Alias Sketch. Can you tell me something about it? How good is it for modelling? I've heard it does NURBS, but no trimmed surfaces. I'm mostly interested in the modelling tools…>> Hi David, Glad to fill you in on Sketch. Yes, it uses NURBS. It uses a single modelling window rather than a 4 view approach which you may be more familiar with. You can and often do work in a perspective view, construction directly in 3D although standard plan and elevation type views are also available. It uses working planes to construct on. One nice (wonderful in fact) feature is the way that *any* existing surface can be made active and you can then construct directly on that surface. As a simple example, you can construct a table, then make the top surface of the table active and construct a vase directly on the surface. As a more complex example, you can take a wavy line on a horizontal plane. Extrude it vertically to get a curtain. Push and pull it around a bit to make a curtain that billows rather than just dropping vertically. Now make the resulting surface 'active', ie what you do next happen ON or RELATIVE to this surface. Select the circle tool and you can draw a circle directly on the surface, wavy though it is. Although Sketch doesn't have tools for boolean operations, you can often fake the effect. In this example you'd duplicate the circle a couple of times. Use the original and TREAT AS HOLE – you'll get a transparent 'hole' in the curtain. Move the others away from the curtain and sweep a surface over the circles and you'll get a wavy hollow tube that you can look into, that interesects the curtain, perfectly joined to it. Sketch does not have trim tools. eg you can't take say, a cube, make a plane that cuts through the cube and 'cut' the cube with the plane. Sketch has snaps to grids and surfaces, although it's not as good as say the smart cursor for 2D drafting in MiniCad/Blueprint. Once you get used to adjusting the snaps as you go along you'll find that you can construct very precisely indeed. It's got a few primitives such as circular faces and square faces, cubes and spheres. It's real strength lies in the extrusion tools. You construct a line, either on a flat surface or in 3D space, using multiple working planes, and you can then sweep objects along this curve to make simple tubes or more complex objects. You can sweep a surface over multiple profiles kind of like a 'skin' function from Strata. All surfaces can be pushed, pulled, kinked and twisted since they're NURBS surfaces. What else ? There's an assembly view, which is a list of every single element, face, line and group in the model, that follows the same structure of groups that you impose when you create. It makes selecting things very easy indeed and makes organising or changing the orgnisation of your model simple. There are various light tools, ambient, point/omnidirectional, spot and sun/parallel. There's a perspective matching tool that's an honest to goodness miracle if you ever have to make your model fit the perspective of an existing photo scanned in as a backdrop. If you ever work with say architects or product designers, it'll save you *hours* of frustrating fiddling around trying to match the viewpoint of your model with the viewpoint of a photo. The rendering quality possible is outstanding although there are a couple of minor 'gotcha's' re shadows and transparency in the Phong rendering engine. The Ray Tracing is simple superb, although even on a PowerMac it can take many hours for a complex situation – still, what do you expect from Ray Tracing 🙂 The texture mapping options are flexible and I've not yet come across a requirement for a texture mapping situation that it couldn't handle. One place where Sketch really excels is it's manuals. Other than the manuals for UpFront I've never seen *any* manuals, let alone those for 3D modellers or CAD applications that even came close. It's clearly laid out and utterly logical. There are tutorials (as well as a video which takes you through the same excercices) which introduce you painlessly to the way Sketch works. There's a 'how to' guide on achieving texture mapping and rendering effects as well as constructing normally difficult objects such as cogs and gears, and how to fake the effect of some boolean operations. There's also straightforward advice on optimising rendering parameters. Finally there's a reference section that breaks down each and every tool and command organised so thatyou never need spend more than about 5 seconds flipping through to find what you want. I kid you not, the manuals are OUTSTANDING ! Import/export to/from other 3D modellers is always fraught with difficulties but it's got a great 3D DXF export facility with the ability to set about a dozen or so parameters to fine tune the flavour of DXF it outputs for the requirements of the system you're exporting to. It's got a pretty robust DXF import too, although that can be more problematical because most modellers just do a 3D DXF export, in the blind confidence that what *they* call a DXF files is the same as what everyone else calls a DXF file. It rarely is of course. If however the source of the DXF doesn't have any options for changing the way it describes objects in the DXF, you're stuffed if you can't read it since there's nothing to fiddle with. What kind of stuff do you model ? Would you expect to be using Sketch as your rendering environment of would you export to something else for that and for animation ? I'm an architect and I've been using Sketch professionally for about a year and other than wishing it had trimming/pseudo booleans for surfaces it's more or less perfect for my needs. It has no animation tools at all. It is strictly a modeller/renderer for still images. Sketch has been reviwed recently in MacUser (UK edition) and maybe in the US mags as well. Let me know if you have any more questions. >> David <<