Nurbs blurbs in SSE and SSE 2

IN MY INVESTIGATION of who uses better implementation of new marchitechture in Geforce 3 with Polynomial surfaces and in the upcoming ATI Radeon 2 with its own Truform using N patches, I have found out some interesting facts.

These come from a conversation with an Intel staffer responsible for SSE and who made a presentation about SSE in the Meltdown 2001 DirectX conference.

Nvidia apparently uses a feature called B-Splines that provide a subset of features which NURBS can provide.

Basically, NURBS provides exact representations of conic surfaces (spheres being the most obvious example). With simple B-spline surfaces, you can only approximate conics which leads to an imperfect sphere but which is rendered with less information than you would need if you used raw polygons.

In addition, NURBS lets you do transformations, including projection transformation, on the control points of the surfaces and then tessellate the surface into triangles.

With B-Spline surfaces, you have to tessellate first, and then do a projection transformation of each of the generated vertices that make up the triangles.

GeForce 3 probably uses b-splines because they are simpler to implement in hardware, but they're not great solution - they are just one step in evolution of graphic. As you may know most modeling packages (3D Studio MAX, Maya, and Lightwave) already have support for NURBS surfaces.

Both Intel and AMD have NURBS (Non Uniform Rational B Splines) in SSE and in the Intel Pentium 4 you even have more functions than are used to reduce the heavy calculation that need to be done in order to get final image from NURBS.

SSE2 provides even more support for 3D and other multimedia techniques. Some of the instructions added with SSE2 round out what was already available with SSE and MMX.

In particular, though, SSE2 adds support for SIMD double-precision floating point arithmetic and support for 128-bit (16-byte) integer operations like those provide by MMX (which only supports 64-bit operations).

This means that these instructions are really interesting since they actually can make thing run faster. NURBS is still not reality but we can expect to see some cards maybe even in Spring next year. Nurbs are hard to calculate but necessary for approximation of real world. And that is what we all would like - Realistic 3D world. µ