<< Part 3
Another area that can frequently be a problem in CAD programs is “vertex only” lighting. That’s when the shading calculations are only exactly calculated at the vertices of the display triangles and then just the color by itself is blended inside the triangles (Gouraud shading). That tends to create a “mach banding” artifact which leaves a sort of visual imprint of the triangles in the display. It’s particularly a problem when specular highlights (white shiny spots) are being used and when the mesh is too coarse. Having a lot of artifacts like that present in the display all over the place also tends to make it more difficult to see the actual surface quality.
In MoI this is improved in 2 ways. One is with a denser tessellation as explained in part 3 of this series. But in addition to that in MoI v2 lighting is done using a cubic environment map rather than vertex-only lighting. This is another area where Direct3D is very practical, because cubic environment mapping was introduced in Direct3D 7.0 and was supported in the very first GeForce and Radeon cards, so it’s very widely supported even on very basic and old hardware.
Also by using Light mapping MoI’s display is not limited to only a small number of lights. It is able to use any number of lights that it wishes without any performance penalty because all the lighting information goes into the environment texture during initialization rather than being treated individually at display time. The default MoI v2 display uses a setup of 12 lights – 1 key light, then 10 low intensity fill lights distributed evenly between two locations, and then one additional fill shining downwards. Having this distributed range of lower intensity lights tends to help put more illumination on the model, preventing overly dark areas. MoI also has some options to enable a metallic/reflective type effect, enable specular highlights and to switch between a couple of different lighting setups.
If most of this is going over your head, no problem. These next couple of images will not.
The truly extraordinary thing is that all these screen shots were taken on a Radeon 9600 Pro, which is a 7 year old graphics card!
Michael says, “It’s a nice benefit to many users to get this kind of high display quality on modest graphics cards. But it’s not only a help for older machines. There are actually many brand new machines sold today that have low powered graphics hardware in them. It’s particularly prevalent with inexpensive laptops and netbooks. These do not have the horsepower to do really heavy scenes, but they can handle simple projects fine. It’s a shame when some CAD program won’t even run on them at all because they don’t have a $1000 video card or “certified drivers” or stuff like that.”
The real goodness is in the next part.
Part 5 >>