[Computación Gráfica] Terminología 3D

El Hombre Gris · 07-09-08, 05:42 PM

Saben que rompo mucho las pelotas con la terminología, y este artículo que leí me viene como anillo al dedo para abrir una discusión sobre terminología en el área de computación gráfica para 3D:

http://beautifulpixels.blogspot.com/...logy-rant.html

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BiTangent vs BiNormal

A BiNormal is defined in calculus as the cross product between a curve's Normal and Tangent. BiNormal is frequently misused in graphics when people need a basis to use on a 2D manifold surface. In that case, there is only one normal, but an infinite set of tangents. Normal mapping typically uses the tangents oriented by the u or v parameterization on the surface. NBTs are really “Normal, BiTangent, Tangent” sets.

Zoom vs Dolly

Misused when people actually mean dolly in-out. They’re confused that “making something bigger on screen” means “zooming”. Zoom a change in the field of view of a camera (by changing the focal length). This is definitely different than dolly… and we’d have no Alfred Hitchcock’s Vertigo without them both!

Hardware vs. Software

I hear this all the time, and it does bug me: "we should run that on the hardware, using a pixel shader". So the GPU is "hardware"? What's the CPU, then? Corrupting the term is kind of pointless, so let's call it the GPU or the graphics accelerator or the graphics card or whatever, but save "hardware" to mean CPU or GPU (or all those other random electronic bits inside the box). The flip side is calling the CPU "software", as in, "well, we can't run it on a pixel shader, so we'll need to run it in software". The CPU and GPU are both controlled by software.

Clipping

The most annoying one for me. Reviewers like to use it and so does production or upper management. What they really mean is geometry penetrations between characters and other characters or characters and world geometry/objects. It doesn't affect gameplay at all but Indy got docked major points for it by IGN and other reviewers.

Maybe they are referring to the graphic engine clipping the character by the geometry? Not sure, they never really explain it. They usually say the character clips into the world or something lame.

Orthonormal Matrix

In the "don't taunt the mathematicians" category, "orthonormal matrix" is not a term most mathematicians use. A matrix composed from mutually perpendicular vectors, with all vectors normalized, in mathematics is normally called an "orthogonal matrix" - there is no term "orthonormal matrix". Well, there are a few rebellious mathematicians and their engineer lackeys who will daringly use "orthonormal matrix", especially after having a little too much sugar in their tea, but this is not a generally accepted term. It's illogical to me that such a matrix is "orthogonal" and not "orthonormal", since "orthonormal axes" and "orthonormal basis" is perfectly fine usage, but that's how it is in mathematics.

Frustum vs Frustrum

It’s Frustum… not Frustrum

Bezier segments and B-spline

[Some] seem to refer to a sequence of Bezier segments as a "B-spline". You can convert one to the other, but that doesn't mean they're the same thing!

Phong shading

Phong shading: this term means two very different things. One usage is synonymous with "Phong interpolation", or per-pixel lighting. This used to be the main meaning of "Phong shading", vs. "Gouraud shading" (vertex interpolation). The other usage really means "Phong lighting" or "Phong illumination", and this is generally what is meant by "Phong shading" nowadays, as in "Blinn-Phong shading model". "Shading model" has come to mean "lighting model", vs. its ancient meaning of "type of interpolation". We still cope by using context: "Phong shading" usually means the specular-highlight cosine-lobe lighting model, but if we see the word "Gouraud" nearby we know it means interpolation instead. Must confuse newcomers, however, so it's probably better to say "Phong interpolation" if you have to say it at all, and best is probably "per-pixel lighting" and let Phong's association with interpolation die out.

Dot3 Bump Mapping

It's not bump mapping, it's normal mapping.

Texture vs Texture Map

[People will say,] "Let's apply a texture map of a brick wall here", when what really should be said is simply "texture" instead of "texture map". The "map" part of "texture map" refers to the function used to transform a surface location in space to a location on the texture.

Overload vs. override

People generally mean override when referring to virtual functions in a subclass, but I routinely hear people use overload for that situation.

Ethan Rourke · 08-09-08, 10:44 AM

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Clipping (Kevin Cristensen)

The most annoying one for me. Reviewers like to use it and so does production or upper management. What they really mean is geometry penetrations between characters and other characters or characters and world geometry/objects. It doesn't affect gameplay at all but Indy got docked major points for it by IGN and other reviewers.

Maybe they are referring to the graphic engine clipping the character by the geometry? Not sure, they never really explain it. They usually say the character clips into the world or something lame.

Jaja, esta me dio gracia, en especial porque tengo el juego y recuerdo dicha review.. suena resentido.
Ojo, no tengo casi idea de la terminología de ese ámbito, pero en este caso Clipping me parece que es un término ampliamente aceptado (por mas que el autor diga que el significado de Clip no tenga que ver con lo que sucede)..
Mas aún, el autor parece no proponer una alternativa a "geometry penetrations between characters and other characters or characters and world geometry/objects"

Y la parte de "It doesn't affect gameplay at all", depende... puede afectar la inmersión en el juego (o como sea que le llamen) no se si el gameplay abarcara eso o no (tengo una definición poco concreta del término).

PD: El juego al que supongo se refiere, esta bueno.. pero se queda muy corto comparado con los títulos anteriores

Dr.D · 04:09 PM

/EDIT: Bleh... tengo que agarrar los libros urgente...

Fuyutski · 08-09-08, 03:16 PM

Código:

1 0 0
0 3 0
0 0 5

No es ortogonal esta matriz, aunque tenga rango 3. Creo que no recuerdo haber escuchado el termino ortonormal para matrices, sino para una base de un k-espaciovectorial. Pero puede ser.
Un ejemplo de matriz ortogonal sería

Código:

sen(a) cos(a)
cos(a) -sen(a)

Saludos!

Dr.D · 03:37 PM

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Mensaje original enviado por Fuyutski

No es ortogonal esta matriz

Este, es dolorosamente obvio que meti la pata...

S h u a n K · 08-09-08, 03:30 PM

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Mensaje original enviado por Fuyutski

Código:

1 0 0
0 3 0
0 0 5

No es ortogonal esta matriz, aunque tenga rango 3.

Saludos!

La condicion para que una matriz sea ortogonal es A*A(transpuesta)=I

Fuyutski · 08-09-08, 03:32 PM

No, una matriz A cuadrada es ortogonal si A.A^t es la identidad.
PD: es cierto que A seria ortogonal si y solo si el conjunto de vectores fila o culumna es ortonormal.

S h u a n K · 08-09-08, 03:34 PM

y que dije yo?

Igualmente, tenias razon en que la matriz de D no es ortonormal.

Una matriz A es ortogonal si y sólo si sus vectores filas o vectores columna son cada uno un conjunto ortonormal de vectores.

Para que sean ortonormales , aparte de ser un conjunto ortogonal tienen que tener norma 1, y los vectores de D no la tienen, la primer fila vale 1, pero la otra vale 3 , y la otra 5 (hablando de las normas.)

Dr.D · 08-09-08, 03:38 PM

Verdad... dije cualquier cosa

Fuyutski · 08-09-08, 03:39 PM

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Mensaje original enviado por Shuankete

y que dije yo?

Igualmente, tenias razon en que la matriz de D no es ortonormal.

Una matriz A es ortogonal si y sólo si sus vectores filas o vectores columna son cada uno un conjunto ortonormal de vectores.

Para que sean ortonormales , aparte de ser un conjunto ortogonal tienen que tener norma 1, y los vectores de D no la tienen, la primer fila vale 1, pero la otra vale 3 , y la otra 5 (hablando de las normas.)

Perdón, pero mientras escribía mi respuesta contestaste primero. Saludos.

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