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3D Primer – page 4

3D Primer – page 4

3D Primer  page 1 | page 2 | page 3 | page 4 | page 5

 

4.01 About the basic toolset

 

This section describes some of the basic tools and `ways of working` that you will find in Sub-division modelling programs. They have different names in different packages so I have tried to include the more common descriptions here. There are lots of Tools not covered in this Primer but once you have mastered the Tools listed here you should be more than confident to go on and explore the hundreds of other Tools, Commands, Features, Scripts and Plugins that you can find in todays 3D Software packages.

In fact, you may go on to write your own!

 

4.02 Managing objects and surfaces

 

Every program has a different type of object management. By object here I mean a piece of geometry that is isolated from another one. An example might be a head: The head is one object, each eye is another, the teeth will be defined as another etc. Some programs use a layer system where each object can be placed on a layer and can be isolated by turning that layer off or simply making it an un-editable wireframe.

 

 

Programs often have a hierarchical list system where each object receives a name and can be selected from this list as needed. Usually only items that are selected/highlighted can be acted upon. Also, it is usual to find grouping and surface naming which allows for easy selection as the model becomes more complex. Using the head as an example again you may decided to group all the teeth together in a set but also give each one a different surface allowing you to select the whole set or just an individual tooth.

Regardless of the software that you choose it is imperative that you plan your modelling and think about grouping and naming parts well before you touch any geometry. Make things easy for yourself and don’t become sloppy in your approach to modelling. Laziness early on in a models creation will lead to frustration for you at a later stage when you want to go back and isolate a part of the mesh.

Remember! Object and Surface management is handled differently in every 3D program: Take time to appreciate what your program can and can’t do.

 

4.03 Rotate, zoom, dolly and the viewports

 

 

An understanding of your programs basic movement/navigation tools is essential for you before you ever touch a model. Each program differs slightly and uses different keyboard/mouse configurations but you will need to know these three without even thinking about them if you are to become a proficient modeller in the package of your choice.

Basically these navigation tools help you to move around the model to help you build it in 3D. It is you/your viewpoint not the model being moved around inside the virtual workspace.
Rotate is like arcing around your model and usually depends on what you have selected.
Zoom is like you walking backward and forwards to and from your model.
Dolly/Pan is like you side stepping left or right.

Add to these such features as roll, bank, walk through, dolly up/down etc. and you will have free reign in your virtual modelling world.
Remember! Learn it and learn it well. If you can’t navigate your workspace efficiently you won’t progress very quickly. Navigation shortcuts are the first shortcuts that need imprinting on your subconscious or post-it-noting to your monitor sides.

 

Not all modelling packages work on the Camera/3D virtual workspace principle. ZBrush has a fixed viewpoint (no camera at all) and the models are presented in an isometric view by default. Lightwave has two modules (Modeller and Layout). `Modeller` doesn’t have cameras as such but does allow most of the navigation described above.

 

Viewports

 

Once you have a good grasp of how to move around your 3D World you can start to look at it from different viewpoint and to do this you need to understand Viewports.

So far I have only described things as seen from the `Perspective viewport`. In most programs you have the option of viewing your scene from the top, bottom,front, back, left or right. You can usually have a number of viewports open at once which is commonly know as a Quad view. This can be very helpful when modeling complex meshes as you can see what is going on from a number of angles all at once.

 

 An Example of a quad view layout from Cinema4D

 

 

4.04 Rotate, zoom, dolly and the viewports

 

XYZ and the workspace

 

Before moving on we need to understand how we know what position these component parts have in the 3D world.

In most 3D Modeling packages the Move, Rotate and Scale function will work relevant to the objects pivot point or its place in the 3D Workspace. Every Object has its own center point or Pivot point. Each componant part also has its own Pivot point.

The workspace for most packages is defined by a 3D space that has a world centre at position 0 (zero). Every model (and it’s component parts) have relative positions in this world as defined by X, Y and Z axis and the relative distance from world centre, negative or positive.

In everyday terms, if you were to look at an object from the `front` (actually down the Z axis) then:

  • Up and down is the Y axis. Plus and minus up and down the Y axis.
  • Left and right is the X axis. Plus and minus left and right across the X axis
  • In and out is the Z Axis. Plus and minus in and out of the Z axis.

 

The Polygon Object componants

 

So now you can move your own viewpoint around inside this virtual world, how do you move your model or a part of your model?
Most programs use a system that allows you to select an object either as a whole or by individual components.

A 3D model can be broken down as follows:

  • Object (The object or model as a whole)
  • Polygon Edge (Edge)
  • Polygon face (Face)
  • Point or Vertices (Vert).

Move, Rotate and Scale

Each of the componants that make up an object (and the object itself) can be selected and acted upon in a number of ways most commonly:

 

  • Componants and Objects can move along X,Y and Z or freely in 3D space.
  • Componants and Objects can be scaled as a whole or along X,Y or Z axis.

When an object or componant part is selected is it common to see a Manipulator of some type (sse the images above) This is a often a multicolored collection of shapes that come together as the manipulator and it can usually change to suit the mode you are in e.g. Move, scale or rotate. Some programs have a manipulator that do all three without changing.

Surface Normals – Or the way a polyon faces

One very important thing to remember is that a Polygon `Face` can point in only one direction. The example below show two primitive shapes. The orange lines are Surface Normals which are lines protruding from the centre of a Polygon Face that can help you to see which way a polygon is facing. All of the faces on these two shapes are facing in the same direction.

If I take away a few of the faces you can better understand what this means to you as a modeler. In the next image you can see where I have removed four polygon faces from the front of the Cube. Now you can see that the Faces of the Cube are transparent from the back indicating that they are facing the other way. You can still see the Surface Normals pointing outwards. This happens because I have switched on a feature called Back Face Culling (in other words `hide the back of the Face`)

In the next image the two Cubes look very similar until you notice that the Surface Normals on the second Cube are all pointing inwards. Both of these Cubes have Back Face Culling turned off so you can see the back and the front of the Polygons Faces. However, on the second Cube I have reveresed the Surface Normals so that they face into the Cube. For a model to be accurate you need to ensure that all your Surface Normals are pointing in the right direction. There is often a feature that allows you to check this or correct it (Unify Normals or Invert Normals)

So back to our Move, Rotate and Scale commands. When working with polygons we want to be able to quickly switch between these components (Usually with Keyboard short cuts).

Tweaking componants

Most packages allow some sort of Tweak feature (A way to rapidly move points into more suitable positions to help define the models shape) and more often than not it is associated with Points/Vertices (although tweaking Edges and Faces is now common place)

This is essential for moving points quickly without having to individually select them. You may have just created a nose using an Extrude command and need to re-shape it to suit your needs. With a few Tweaks the re-located points change the shape completely.

4.05 Mirro mirror


Very often you will want to model a symmetrical object or creature. To save time most 3D packages offer some sort of virtual mirror or symmetry across an axis. Learn how your program of choice does this as it is a real time saver. The mirrored half may only be an Instance of the original half (An Instance is a copy that will up-date and reflect the work you do on the original).

When the modelling is finished you may need to delete the instance copy and use a true Mirror command to generate actual geometry across the axis and the program will usually give you an option to merge the points along the axis joining the two halves.

 

4.06 Adding Edges/Points and Cutting/Splitting Polygons

Tools that add Edges/points and Cut polygons are the staples of Sub-division modelling. To change a models shape and create flowing loops you need to be able to change the way Polygon Faces are formed and how many there are. As there are so many 3D Modeling programs and so many tools within those programs it is hard to list them all. I have tried to describe the main tools that you will see in most programs and a brief explanation where to use them.
Some of tools available are:

Split Polygon Allows you to select an existing point or sometimes a postion along an Edge then select an adjacent Edge or point to add a new point which splits the polygon by adding a new edge.

Knife will run a split through the geometry that it crosses. very useful in Views other than the perspective view.

Split loop/Bandsaw will split polygons in half by adding a new edge down the centre. There is often some way to control Exactly where the split will occur either a slider function, graphically or numerically.

Spin Edge/Spin Quad whilst not a cutting or splitting tool is invaluable when used in conjunction with the other tools. It is used to change the flow of an Edge loop by literally spinning an Edge that falls between two faces thus altering polygon flow.

4.07 Connecting/Collapsing and Merging points

 

Connect: Another common Tool available in most 3D Modeling Packages. Simply select two Vertex and call Connect. An Edge will be created splitting the polygon.

Collapse: With a Face selected call Collapse and the entire Face collapses into a single Vertex.

Merge Vertices or Weld Points does what it says. It takes two or more Vertex and joins them into a Single Vertex. The Vertex that was selected last usually stays put and the one that was selected first moves to the same location and is welded into a single point.

 

4.08 Extruding faces and edges

 

`Extrude` or `Smooth shift` is common to most modeling packages and is used frequently.

Select the component, either a Face or an Edge (If supported) and call the `Extrude` command. This will pull a new Face or Edge from the existing one and fill in the geometry around it.

The Examples of using Extrude below are:

  • Extrude 2 Faces from a Cube
  • Extrude and Scale down a Face
  • Extrude and Inset a Face
  • Extrude 4 Edges from the Cube into 4 new Polygon Faces
  • Extrude 4 Edges creating 4 New Faces

As we are now aware when an object is Sub-divided it becomes visibly smoother.

Smooth, Tighten or Average Vertices are smoothing commands that smooth selected Points (or Edges and Faces in some programs. This can be used to selectively refine the look of an area on a model without adding more geometry or Sub-dividing.

Using Smooth and your programs Tweak mode are the best way to achieve a smooth model in its non-Sub-divided form. The Smoother and more refined you can make your Mesh the better. Of course be careful not to Smooth away the wrinkles and folds that you want to keep. You can go over the top here!

Incidental info:Most 3D Programs have a Smooth Shade option of some type. This is usually a surface attribute and as such alt is neither a Sub-division routine or a smoothing Tool that affects geometry.

ZBrush has several unique smoothing techniques including a Smoothing Brush that allows you to paint an area of mesh and see it interactively smooth. Another unique way is to use an Alpha masking tool to protect part of the model and use a Smoothing deformation Slider to do the smoothing.

 

4.10 Limit the Polygon Count/Adding local detail

 

One of the biggest challenges for the Polygon Sculptor is keeping within a limited polygon count. If you use tools like Split Face Loop a lot you end up with geometry around your model that simply isn’t needed. There have been numerous articles and forum threads about this subject for a long time and here are some of the main ways to add detail in a local area

 

Quads that look like Tri’s:

 

A very well known technique, A four sided polygon that looks like Triangle. This is the simply a way to keep your poly count low. Using Connect/split polygon etc. you can Split a run of Faces that lead to a Triangle. This gives you a Quad that has the look of a Triangle but Sub-divides as a Quad with no errors to worry about.

 

 

Narrowing the field:

 

Essentially the same as the above example, the examples below show how you can reduce the amount of polygons in a set of Face loops. This does create five star poles but if placed correctly these will not create problems for you. It is a common way to allow you to have more detail in one area that is leading into an area of less density e.g. A face and forehead.

 

Adding creases and wrinkles: 

 

There are a great many plug-ins around these days that will do this for you. If you need Wrinkles on a forehead and only want to add local detail you need to Split the Face Loops across the top off the head and run the Loop back on itself.

 

4.11 Moving points with a magnet

At differing stages during a models creation you may need to move portions of the mesh around to achieve the required shape. Doing this point by point is tedious hence the need for a magnet tool also called Soft selection or Dragnet. There is often a way to adjust the falloff or influence amount allowing greater or lesser amounts of movement.

 

 

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