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** ATI Developer Relations Newsletter
- April 2001 **
1.0 N-Patch Update
Details on ATI's N-Patch surface and enhancements in DirectX 8.1
Curved PN Triangles paper and extension
Updated ATI N-Patch Plug-in for 3D Studio MAX R3
2.0 ATI GDC2001 Presentations
Vertex Shading with Direct3D and OpenGL
3.0 Linux / XFree86 Developments
4.0 ATI On-Board
ATI Design Wins
5.0 ATI Announcements
ATI Press Releases
6.0 Contacting Us
Developer Support
1.0 N-Patch Update
It's no secret that ATI created N-Patches (aka Curved PN Triangles). Although we have not yet announced a product which supports this feature, we are actively evangelizing the use of N-Patches as an easy way for you to upgrade your geometry content for the next generation of graphics processors. If you haven't started playing with N-Patches, check them out today!
Quick N-Patch Overview
Briefly, N-Patches are a means of creating a higher-order
surface from a traditional triangle dataset. The input
to a chip that supports N-Patch tessellation is the same
as the input to an existing graphics processor that renders
triangles. This means that you can take advantage of N-Patches
without drastically affecting your art pipeline. It also
means that you are backward compatible with existing graphics
chips, since the inputs (vertex buffers or vertex arrays)
are identical.
Since any higher-order surface is essentially a form of compression, you can improve graphics memory usage as well as memory bandwidth by using relatively low polygon meshes and tessellating them on-chip with N-Patches. The increased number of vertices smoothes out your silhouette edges and improves the quality of vertex shading computations such as specular highlights.
Cracks / Creases
One attack that detractors like to use when arguing against
use of N-Patches is that cracks can be generated between
patches. This is true of all rendering primitives, including
triangles. If your model is broken, your model is broken.
T-junctions in triangle data will result in cracks; you've
been authoring with this in mind for years now. N-Patched
models can result in cracks if you don't generate crease
polygons where needed (at edges with non-shared normals)
but it's easy to author around this in a manual or automated
way using our tools. All rendering primitives can
result in cracked models if misused. You've been authoring
around triangle T-junctions for years, and you can author/preprocess
around this kind of artifact for other primitives as well.
We have just released a new version of our N-Patch preview plug-in for 3DS MAX R3.1 and R4 which will show you where crease polygons must be inserted to prevent cracking. This is done by examining the smoothing groups and inserting crease polygons. We have also provided a sample exporter which inserts the crease polygons automatically according to smoothing group information.
DirectX 8.1 API - More control of interpolation order
In DirectX 8.0, N-Patches were exposed via the D3DRS_PATCHSEGMENTS
render state. As long as you've created a vertex buffer
with the D3DUSAGE_NPATCHES flag and the vertex
buffer has positions and normals, you can just draw with
the usual DrawPrimitive() entrypoints. By
default, you will see cubic interpolation of positions
and linear interpolation of normals.
In DirectX 8.1, you have more control over the interpolation order of the positions and normals of the generated vertices. Specifically, the new D3DRS_POSITIONORDER and D3DRS_NORMALORDER render states control interpolation order. The position interpolation order can be set to either D3DORDER_LINEAR or D3DORDER_CUBIC. The normal interpolation order can be set to either D3DORDER_LINEAR or D3DORDER_QUADRATIC.
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Curved PN Triangles Paper
We presented the paper Curved PN Triangles, which outlines
the motivations and mathematical foundations of N-Patches,
at the 2001
ACM Symposium on Interactive 3D Graphics just prior
to jetting out to GDC. An electronic
copy is available at the ATI Developer Relations website.
Here is the full citation:
Alex Vlachos, Jörg Peters, Chas Boyd and Jason L. Mitchell, "Curved PN Triangles" ACM Symposium on Interactive 3D Graphics 2001, pp. 159-166.
OpenGL Extension
The ATIX_pn_triangles
extension is emulated in the latest OpenGL drivers. This
means that performance will be very slow, but you can
prototype on it and get your interface in place. We recommend
that you preview your art in our 3DS
MAX R3 plug-in to get a feel for how the art will
look when it is tessellated with N-Patches.
The tessellation level and interpolation orders are specified with the new entrypoint:
glPNTriangles{if}ATIX(enum pname, Tparam)
- For example, to set the normal interpolation order, use one of the following:
glPNTrianglesiATIX (PN_TRIANGLES_NORMAL_MODE_ATIX,
PN_TRIANGLES_NORMAL_MODE_LINEAR_ATIX);glPNTrianglesiATIX (PN_TRIANGLES_NORMAL_MODE_ATIX, PN_TRIANGLES_NORMAL_MODE_QUADRATIC_ATIX);
- To set the position interpolation order, use one of the following:
glPNTrianglesiATIX (PN_TRIANGLES_POINT_MODE_ATIX, PN_TRIANGLES_POINT_MODE_LINEAR_ATIX); glPNTrianglesiATIX (PN_TRIANGLES_POINT_MODE_ATIX, PN_TRIANGLES_POINT_MODE_CUBIC_ATIX);
To set the tessellation level, use glPNTrianglesiATIX (PN_TRIANGLES_TESSELATION_LEVEL_ATIX, tessLevel);
To turn tessellation on and off, use
glEnable(PN_TRIANGLES_ATIX); and glDisable(PN_TRIANGLES_ATIX);
N-Patch Plug-in for 3D Studio MAX R3
We have an N-Patch preview plug-in for 3DS MAX R3 and R4 available on our website: http://www.ati.com/developer/sdk/NPatch/NPatchPlugin.html.
We have just added the ability to visualize crease polygons which must be inserted to preserve crease edges as well as a sample exporter to automate this process.
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2.0 ATI GDC2001 Presentations
- ATI Presented the following sponsored sessions at GDC and the slides are now online:
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3.0 Linux / XFree86 Developments
The most recent information on ATI Linux support is found at http://www.ati.com/developer/linux.html.
XFree86 4.0.3 contains support for Radeon, RAGE 128 PRO 2D / 3D and overlay. Dual-display support for Radeon VE and Mobility Radeon due to be release Q2'01.
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4.0 ATI On-Board
ATI has announced Design Wins with Dell, IBM, Compaq, Gateway, Micron, NEC, Acer, Toshiba, HP, and Sony.
See http://www.ati.com/onboard/onboard.html
for more information and check here often for new design
wins in all our target markets.
ATI Design Wins
Notebook Systems - http://www.ati.com/onboard/index.html
Desktop Systems - http://www.ati.com/onboard/index.html
Set-Top Box Systems - http://www.ati.com/onboard/index.html
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5.0 ATI Announcements
For the latest Press Releases see http://www.ati.com/companyinfo/press/2001/index.html
April 3, 2001
ATI completes acquisition of FGL Graphics from SONICblue
March 19, 2001
ATI receives Peak Performer™ Award at recent international System Builder Summit™
Company’s targeted system builder strategy wins praise
February 19, 2001
ATI now shipping Radeon® VE board, the ultimate mainstream graphics solution featuring Hydravision™ multi-monitor support
Furthers ATI's commitment to leadership in retail space
February 13, 2001
ATI endorses AMD’S HyperTransport™ technology
Industry-standard technology designed to accelerate graphics processing
February 5, 2001
ATI unveils Mobility™ Radeon®: world's highest performance, most feature-rich graphics processor for the notebook PC
Extends critically-acclaimed Radeon® technology to mobile PC market
January 10, 2001
ATI and Intel sign cross-licensing agreement
January 9, 2001
ATI graphics chips and boards ship in new Apple desktop and mobile products
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6.0 Contacting Us
E-mail: devrel@ati.com
Hotline: (905) 882-2636
Fax: (905) 475-3930
Developer Relations
ATI Technologies Inc.
75 Tiverton Court
Unionville, Ontario
Canada L3R 9S3
ATI Developer Relations Web Site http://www.ati.com/developer/index.html.
Head Office, Sales and Marketing Phone: (905) 882-2600
World Wide Web: http://www.ati.com/
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** ATI Developer Relations Newsletter **
Copyright (c) ATI Technologies Inc. 2001. All company and/or product names are trademarks and/or registered trademarks of their respective manufacturers.
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