What's new in DX 9.0c


This year the latest in the DirectX API is getting a bit of a face lift. The new feature in DirectX 9.0c is the inclusion of Pixel Shader and Vertex Shader 3.0. Rather than calling this DirectX 9.1, Microsoft opted to go for a more "incremental" looking update. This can end up being a little misleading because whereas the 'a' and 'b' revisions mostly extended and tweaked functionality, the 'c' revision adds abilities that are absent from its predecessors.

Pixel Shader 3.0 (PS3.0) allows shader programs of over 65,000 lines and includes dynamic flow control (branching). This revision also requires that compliant hardware offer 4 Multiple Render Targets (MRT's allow shaders to draw to more than one location in memory at a time), full 32-bit floating point precision, shader antialiasing, and a total of ten texture coordinate inputs per pixel.

The main advantage here is the ability for developers to write longer, more complex, shader programs that run more efficiently. The flow control will give developers the freedom to write more intuitive code without sacrificing efficiency. Branching allows a shader program the expanded ability to make decisions based on its current state and inputs. Rather than having to run multiple shaders that do different things on different groups of pixels, developers can have a single shader handle an entire object and take care of all its shading needs. Our example of choice will be shading a tree: one shader can handle rendering the dynamics of each leaf, smooth new branches near the top, rugged old bark on the trunk, and dirty roots protruding from the soil.

Vertex Shader 3.0 extends its flow control ability by adding if/then/else statements and including the ability to call subroutines in shader programs. The instruction limit on VS3.0 is also extended to over 65000. Vertex textures are also supported, allowing more dynamic manipulation of vertices. This will get even more exciting when we make our way into the next DirectX revision which will allow for dynamic creation of vertices (think very cool particle systems and hardware morphing of geometry).

One of the coolest things that VS3.0 offers is something called instancing. This functionality can remove a lot of the overhead created by including multiple objects based on the same 3d model (these objects are called instances). Currently, the geometry for every model in the scene needs to be setup and sent to the GPU for rendering, but in the future developers can create as many instances of one model as they want from one vertex stream. These instances can be translated and manipulated by the vertex shader in order to add "individuality" to each instance of the model. To continue with our previous example, a developer can create a whole forest of trees from the vertex stream of one model. This takes pressure off of the CPU and the bus (less data is processed and sent to the GPU).

Now that we've seen what developers are looking at with DirectX 9.0c, let's take a look at how NVIDIA plans to bring these features to the world.
Index NV40 Under the Microscope
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  • Pete - Monday, April 19, 2004 - link

    Shinei,

    I did not know that. </Johnny Carson>

    Derek,

    I think it'd be very helpful if you listed the game version (you know, what patches have been applied) and map tested, for easier reference. I don't even think you mentioned the driver version used on each card, quite important given the constant updates and fixes.

    Something to think about ahead of the X800 deadline. :)
    Reply
  • zakath - Friday, April 16, 2004 - link

    I've seen a lot of comments on the cost of these next-gen cards. This shouldn't surprise anyone...it has always been this way. The market for these new parts is small to begin with. The best thing the next gen does for the vast majority of us non-fanbois-who-have-to-have-the-bleeding-edge-part is that it brings *todays* cutting edge parts into the realm of affordability. Reply
  • Serp86 - Friday, April 16, 2004 - link

    Bah! My almost 2 year old 9700pro is good enough for me now. i think i'll wait for nv50/r500....

    Also, a better investment for me is to get a new monitor since the 17" one i have only supports 1280x1024 and i never turn it that high since the 60hz refresh rate makes me go crazy
    Reply
  • Wwhat - Friday, April 16, 2004 - link

    that was to brickster, neglected to mention that Reply
  • Wwhat - Friday, April 16, 2004 - link

    Yes you are alone Reply
  • ChronoReverse - Thursday, April 15, 2004 - link

    Ahem, this card has been tested by some people with a high-quality 350W power supply and it was just fine.


    Considering that anyone who could afford a 6800U would have a good powersupply (Thermaltake, Antec or Enermax), it really doesn't matter.


    The 6800NU uses only one molex.
    Reply
  • deathwalker - Thursday, April 15, 2004 - link

    Oh my god...$400 and u cant even put it in 75% of the systems on peoples desks today without buying a new power supply at a cost of nearly another $100 for a quailty PS...i think this just about has to push all the fanatics out there over the limit...no way in hell your going to notice the perform improvement in a multiplayer game over a network..when does this maddness stop. Reply
  • deathwalker - Thursday, April 15, 2004 - link

    Reply
  • Shinei - Thursday, April 15, 2004 - link

    Pete, MP2 DOES use DX9 effects, mirrors are disabled unless you have a PS2.0-capable card. I'm not sure why, since AvP1 (a DX7 game) had mirrors, but it does nontheless. I should know, since my Ti4200 (DX8.1 compatible) doesn't render mirrors as reflective even though I checked the box in the options menu to enable them...
    Besides, it does have some nice graphics that can bog a card down at higher resolutions/AA settings. I'd love to see what the game looks like at 2048x1536 with 4xAA and maxed AF with a triple buffer... Or even a more comfortable 1600x1200 with same graphical settings. :D
    Reply
  • Da3dalus - Thursday, April 15, 2004 - link

    I'd like to see benchmarks of Painkiller in the upcoming NV40 vs R420 tests... Reply

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