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

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.

try http://www.nintendo.com/n64/n64terms.htmlQuote:>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?

there are some definitions of what they are, and may be a bit nintendo

specific, but they`re there!

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.

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.

>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

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

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

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