EverettP
06-01-2002, 02:19 AM
Sorry to be ignorant, but what are they? (SubDs)
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bigfatMELon
06-01-2002, 02:38 AM
Subdivision Surfaces. A form of modeling where a low resolution cage is used to define a higher resolution output. It offers few technical requirements and localized detail.
-jl
-jl
enforcer2k
06-01-2002, 03:31 AM
SubD basically means Subdivision.
Okay subdivision of what you ask? Polygons.
Why would you want to do this? It's useful for creating smooth shapes from polygons which is hard to do by just adding more points and edges directly to the model.
How are Subds used in practice? Well two basic parts to subd modelling
(1) The cage - This is the basic polygon mesh that defines the shape of the model you want to create
(2) The subdivided mesh - This is the smoothed surface created by subviding the cage a given number of times. The number of times a cage is subdivided is normally referred to as iterations.
What the hell are Iterations? Well if you have a single four sided poly, one iteration result in 4 polys, ie. each edge is divided one time. Hence, if you have 2 iterations on the four sided, the poly is smoothed by creating 16 polys. So by increasing the number of iterations, you can make your model smoother and more realistic.
What if I want a mix of sharp edges and curved ones (A car? A robot? A toaster?) ... The Subd approach is naturally given to making curved surfaces from flat polys. Defining sharps edges in subs can be done in 2 major ways (more in some applications).
(1) The first way would be to create edges close to each other... this make the interpolation so small that it appears sharp (there will be a little curvature most times, but this is fine because edges in nature, even on things such as knives are rarely totally sharp, and using a single poly edge for such edges will give you unrealistic light and shading effects)
(2) Method 2 for making edges is to add weights to the vertices that make up the edges, or the edges themselves. This creates a bias in the mesh that <pulls> the curve in simple terms into a straighter line. If this method sounds weird it's because it is, and few modeler's actually like to use it because it can have funky unpredictable effects at times. Nevertheless, most apps let you do this.
(2b) Maya has an edge crease or vertice crease function that can create a crease <sharp/semi-sharp edge> around an edge or a point.
Why did I explain all that crap? Well most objects are a mixture of smooth and semi-smooth, and sharp surface. Think of cheeks and teeth, smooth surface and the later a mix of both.
--------------------------------------
Oh great! I'm psyched so can I just start putting polys anywhere and building realistic models? Yes and no :). SudD modelling is simple in theory, but defining objects realistically takes a little theory (yes, sadly so) and practice.
Bummer, okay what's the main theory I need to know?
1) How to make sharp and soft edges. Ah Easy!
2) How to define the curves in my models. Not so easy eh!? This can be achieved by arranging the cage vertices to approximate the curvature of the surface you are trying to create. So what does this mean? A cheeks slope might take 3 or 4 points to define, it's really not a hard concept at all.
3) EDGE LOOPS!!! Now this takes time. This is basically the art of creating organic surfaces in an anatomically/structurally sound fashion by using interconnected edges that form loops. The easiest way to understand this is to think of eyes and mouths. They are basically circular portals that DEFORM when animated in a cylindrical fashion... Picture lips pursing, kissing, smiling and think of a circle getting wider and smaller etc... When modeling such features, the accurate way to capture them is to used interconnected edges or vertices that form loops moving outwards from the mouth. Same for the eyes etc. Think the same way when creating an arm or fingers. When you model this way it's easy to create wrinkles and animate (or simply deform) you model to capture different realistic states :) Look online for tutorials on the web on this method, but your development of this skill will come mostly from practice and then from personal research.
--------------------------------------------------
Maya subD has more features which I think you should refer to the manual about, what I have described mostly is the cross platform idea which I hope forms an okay basis for your understanding of Subd's in general. :)
---------------------------------------------------
I hope this helps a bit :P
---------------------------------------------------
*Anyone please feel free to correct any errors or omissions I've definitely made :):D
Okay subdivision of what you ask? Polygons.
Why would you want to do this? It's useful for creating smooth shapes from polygons which is hard to do by just adding more points and edges directly to the model.
How are Subds used in practice? Well two basic parts to subd modelling
(1) The cage - This is the basic polygon mesh that defines the shape of the model you want to create
(2) The subdivided mesh - This is the smoothed surface created by subviding the cage a given number of times. The number of times a cage is subdivided is normally referred to as iterations.
What the hell are Iterations? Well if you have a single four sided poly, one iteration result in 4 polys, ie. each edge is divided one time. Hence, if you have 2 iterations on the four sided, the poly is smoothed by creating 16 polys. So by increasing the number of iterations, you can make your model smoother and more realistic.
What if I want a mix of sharp edges and curved ones (A car? A robot? A toaster?) ... The Subd approach is naturally given to making curved surfaces from flat polys. Defining sharps edges in subs can be done in 2 major ways (more in some applications).
(1) The first way would be to create edges close to each other... this make the interpolation so small that it appears sharp (there will be a little curvature most times, but this is fine because edges in nature, even on things such as knives are rarely totally sharp, and using a single poly edge for such edges will give you unrealistic light and shading effects)
(2) Method 2 for making edges is to add weights to the vertices that make up the edges, or the edges themselves. This creates a bias in the mesh that <pulls> the curve in simple terms into a straighter line. If this method sounds weird it's because it is, and few modeler's actually like to use it because it can have funky unpredictable effects at times. Nevertheless, most apps let you do this.
(2b) Maya has an edge crease or vertice crease function that can create a crease <sharp/semi-sharp edge> around an edge or a point.
Why did I explain all that crap? Well most objects are a mixture of smooth and semi-smooth, and sharp surface. Think of cheeks and teeth, smooth surface and the later a mix of both.
--------------------------------------
Oh great! I'm psyched so can I just start putting polys anywhere and building realistic models? Yes and no :). SudD modelling is simple in theory, but defining objects realistically takes a little theory (yes, sadly so) and practice.
Bummer, okay what's the main theory I need to know?
1) How to make sharp and soft edges. Ah Easy!
2) How to define the curves in my models. Not so easy eh!? This can be achieved by arranging the cage vertices to approximate the curvature of the surface you are trying to create. So what does this mean? A cheeks slope might take 3 or 4 points to define, it's really not a hard concept at all.
3) EDGE LOOPS!!! Now this takes time. This is basically the art of creating organic surfaces in an anatomically/structurally sound fashion by using interconnected edges that form loops. The easiest way to understand this is to think of eyes and mouths. They are basically circular portals that DEFORM when animated in a cylindrical fashion... Picture lips pursing, kissing, smiling and think of a circle getting wider and smaller etc... When modeling such features, the accurate way to capture them is to used interconnected edges or vertices that form loops moving outwards from the mouth. Same for the eyes etc. Think the same way when creating an arm or fingers. When you model this way it's easy to create wrinkles and animate (or simply deform) you model to capture different realistic states :) Look online for tutorials on the web on this method, but your development of this skill will come mostly from practice and then from personal research.
--------------------------------------------------
Maya subD has more features which I think you should refer to the manual about, what I have described mostly is the cross platform idea which I hope forms an okay basis for your understanding of Subd's in general. :)
---------------------------------------------------
I hope this helps a bit :P
---------------------------------------------------
*Anyone please feel free to correct any errors or omissions I've definitely made :):D
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