Q: What is HEIDI?
Is it a software driver I can download and install?
Is it a driver I must obtain from the manufacturer of my graphics card (Diamond Stealth Video VRAM with 4 Mb equiped), and can I use it with my graphics card.

A: Heidi stands for HDI, which stands for HOOPS Device Interface, and HOOPS is something like Hierarchical Object Oriented Pipeline System (?) It is a high-end software API developed by Ithaca Software that can (but must not) map to existing hardware-based OpenGL functions. It has some practical advantages to "pure" OpenGL, the most important being the fact that OpenGL has to redraw the whole screen for every frame, HOOPS redraws only the parts of the screen where an obejct has changed. This can signifacally speed up redraws in a modeling environtment like MAX. (To check this you can create a huge scene in MAX, then animate just a single object to move around in front and behind other objects. Then animate tha camera to move around - the whole screen has to be updated and the redraw speed will be much lower. On an OpenGL system both examples would give the same redraw times... This works on every system since the Software Z-buffer driver uses the same technique as a Heidi driver - only without hardware acceleration)

Here some TECHNICAL facts: http://ftp.germany.eu.net/shop/techsoft/hoops/main.htm

Also there is a chapter called "Why 3DS MAX Uses Heidi and Not OpenGL" on the Kinetix page http://www.ktx.com/products/01max/why3ds.htm

Basically, you could download a Heidi driver if one is available. I don't think there is one for your card, currently only expensive hi-end OpenGL-capable cards have Heidi drivers.

NOTE that I am not a software developer or a technician and everything I have written might be wrong ;o)