Hi, I am doing a paper on 3D-boards, and I am looking for definitions

Hi, I am doing a paper on 3D-boards, and I am looking for definitions

Post by Nick Enthov » Sat, 05 Dec 1998 04:00:00



Hi, I am doing a paper on 3D-boards, and I am looking for definitions
for the abilities of those cards, like:
AlphaBlending
Tri-liniear filtering,
TextureMapping,
And more of those 3D features, can anyone help me with these?

Thanx!
Nick.

 
 
 

Hi, I am doing a paper on 3D-boards, and I am looking for definitions

Post by Matt Seale » Sat, 05 Dec 1998 04:00:00



Quote:>Hi, I am doing a paper on 3D-boards, and I am looking for definitions
>for the abilities of those cards, like:
>AlphaBlending
>Tri-liniear filtering,
>TextureMapping,
>And more of those 3D features, can anyone help me with these?

try http://www.nintendo.com/n64/n64terms.html

there are some definitions of what they are, and may be a bit nintendo
specific, but they`re there!

 
 
 

Hi, I am doing a paper on 3D-boards, and I am looking for definitions

Post by Iqbal Maskatiy » Sat, 05 Dec 1998 04:00:00


AlphaBlending - It is the ability to combine colors based on a property
called Alpha, which can range from 0 to 1, ( 0 means Trasparent, while 1
means Opaque ) this allows you to blend colors and create a transparency
effect that enhances the look of such effects as water, fire.. or smoke,
etc, etc.

Texture Mapping - for more realistic effects of an object with certain
material properties ( such as stone or wood ), an image of the material
is applied over the object, like as if you were taking a thin sheet with
the material image printed on it and covering the object on all sides.
Texture mapping along with the object's own geometry attributing to the
shading results in a very very realistic effect that is also quite
efficient for real-time rendering ( as required in those fast paced games
like Quake and Unreal )

Trilinear Filtering - Since texture maps are images of finite size, if
you get real close to an object that is texture mapped, you will see one
pixel of the texture image applied as a big rectangular region. Since in
reality the closer you get to the object, the more detail you see,
trilinear filtering will create a smooting effect between such pixels
when viewed very closely ( well, it is more apparent when you see it more
closely ) thus providing the feel of actual detail existing in the
texture and the object as well. It does so by taking an average of three
of those points ( hence Tri-Linear ) aligned in a triangular fashion ( I
assume ) and smoothing the area within. Bilinear filtering used only two
points, though the more points, the better the look, therefore Trilinear
will look much better than Bilinear. The new type of filtering, Isotropic
filtering provides smoothing in 3D, not only 2D as the previous two I
just mentioned.

If I am incorrect, please correct me.

Nick, I hope this helps... or atleast gets you started.


> Hi, I am doing a paper on 3D-boards, and I am looking for definitions
> for the abilities of those cards, like:
> AlphaBlending
> Tri-liniear filtering,
> TextureMapping,
> And more of those 3D features, can anyone help me with these?

> Thanx!
> Nick.

 
 
 

Hi, I am doing a paper on 3D-boards, and I am looking for definitions

Post by A N Housto » Sun, 20 Dec 1998 04:00:00


The filtering you describe (below) is bilinear and actually uses four sample
points (i.e. four neighbouring pixels) which can be considered as forming two
intersecting diagonal lines (hence bi-linear). The pixels are combined in a
ratio dictated by their proximity to the ideal sample point. For example, if
the sample point lies within a pixel which happens to be green (and the
others are blue) then the resulting sampled colour will have a strong green
bias.

An approximation to bilinear filtering using only three sample points is used
in some graphics hardware to reduce cost (requires only 2 blending operations
instead of 3). Blending and combining operations require flash multipliers
for each channel i.e. R,G,B,A and are consequently very expensive in terms of
an overall silicon "budget".

Trilinear filtering is used in conjunction with MIP (Multiple Image Pyramid)
mapping to blend between two levels of detail and I presume this is what
you're getting at when you mention "smoothing in 3D". Each level of detail is
bilinear sampled then the two are blended together in accordance with the LOD
(Level Of Detail) ratio. Trilinear filtering can also used in conjunction
with multitexturing to generate all sorts of interesting effects, depending
on the capabilities of the hardware. Most systems do trilinear at half speed
(there is, after all, twice as much work to do) but 3DFX and NVidia have
developed technology to do "single pass" multitexturing i.e. there is little
or no performance cost.

I'm not sure how isotropic filtering works (other than isotropic meaning
"equal in all directions") but I presume it's a better alternative to
bilinear. Does anyone out there know how to implement an isotropic filter?

Quote:> Trilinear Filtering - Since texture maps are images of finite size, if
> you get real close to an object that is texture mapped, you will see one
> pixel of the texture image applied as a big rectangular region. Since in
> reality the closer you get to the object, the more detail you see,
> trilinear filtering will create a smooting effect between such pixels
> when viewed very closely ( well, it is more apparent when you see it more
> closely ) thus providing the feel of actual detail existing in the
> texture and the object as well. It does so by taking an average of three
> of those points ( hence Tri-Linear ) aligned in a triangular fashion ( I
> assume ) and smoothing the area within. Bilinear filtering used only two
> points, though the more points, the better the look, therefore Trilinear
> will look much better than Bilinear. The new type of filtering, Isotropic
> filtering provides smoothing in 3D, not only 2D as the previous two I
> just mentioned.

 
 
 

Hi, I am doing a paper on 3D-boards, and I am looking for definitions

Post by Kevi » Sun, 20 Dec 1998 04:00:00



>I'm not sure how isotropic filtering works (other than isotropic meaning
>"equal in all directions") but I presume it's a better alternative to
>bilinear. Does anyone out there know how to implement an isotropic

filter?

It's what you already described. I'm pretty sure the original poster meant
ANisotropic filtering but got the term wrong. It's a complementary
technique to either bi- or tri-linear filtering. IIRC, the basic idea is
that rather than just taking a square box around the ideal point, you bias
the shape of the box to better represent the projection of the texture, so
you might sample from, say, a 4x2 area if you're looking at a square from
a 45-degree angle.

--
Kevin

 
 
 

Hi, I am doing a paper on 3D-boards, and I am looking for definitions

Post by A N Housto » Sun, 20 Dec 1998 04:00:00


Just in case anyone's interested, I did a bit of searching and found a
reasonable explanation of anisotropic filtering (and why it's useful) at:

<http://toolbox.sgi.com/TasteOfDT/src/exampleCode/WitchesBrew/multipas...>

Cheers,
               Al.



> >I'm not sure how isotropic filtering works (other than isotropic meaning
> >"equal in all directions") but I presume it's a better alternative to
> >bilinear. Does anyone out there know how to implement an isotropic
> filter?

> It's what you already described. I'm pretty sure the original poster meant
> ANisotropic filtering but got the term wrong. It's a complementary
> technique to either bi- or tri-linear filtering. IIRC, the basic idea is
> that rather than just taking a square box around the ideal point, you bias
> the shape of the box to better represent the projection of the texture, so
> you might sample from, say, a 4x2 area if you're looking at a square from
> a 45-degree angle.

> --
> Kevin