RE: bilinear filtering from a floating point texture, on Nvidia hardware?

"Pat Brown \(OpenGL\)" <[email protected]> Tue, 23 May 2006 17:54:26 -0800
Newsgroups gmane.games.devel.opengl
Organization Fat City Network Services, San Diego, California
Message-ID <[email protected]>
There are two different sets of float textures supported on NVIDIA
hardware.

The NV float formats were introduced for GeForce FX, which didn't
support any filtering of floating-point textures.  We spec'ed this as a
"feature", for better or worse, in the language you cite below.

When the ARB standardized float textures (ARB_texture_float), we started
with ATI's floating-point texture extension, which didn't have this
limitation.

NVIDIA supports the ARB extension on the GeForce 6 series and up, and
plan to do so going forward.  We still support the NV extension, but we
didn't extend all the capabilities of the ARB extension to the NV
formats.

Pat

-----Original Message-----
Matt Franklin
Sent: Tuesday, May 23, 2006 8:59 PM
To: Multiple recipients of list OPENGL-GAMEDEV-L
hardware?

Hi-- I'm just looking for a bit of clarification regarding bilinear
filtering support under OpenGL vs. DirectX.


The Nvidia GPU Programming Guide lists that it supports filtering from
G16R16F and A16B16G16R16F texture formats (and it does not support
filtering from other float formats, such as R32F).  However, the OpenGL
extension NV_float_buffer documentation specifies:

"Floating-point textures (those with a base internal format of
FLOAT_R_NV, FLOAT_RG_NV, FLOAT_RGB_NV, or FLOAT_RGBA_NV) do not support
texture filters other than NEAREST.  For such textures, NEAREST
filtering is applied regardless of the setting of TEXTURE_MIN_FILTER."
(A similar statement is supplied for TEXTURE_MAG_FILTER.)

Am I correct in deducing that this means the 6 series hardware is
capable of bilinear filtering from floating point textures, however,
this functionality is only available using DirectX?

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-- 
Author: Matt Franklin
  INET: [email protected]

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Author: Pat Brown \(OpenGL\)
  INET: [email protected]

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