Saturday, April 25, 2015

Digital Sculpting - Two Model Pose

Our sculpture group decided to take on the challenge of working with two models. Our first pose had one model on top of the other like this:

After trying that out for a session we changed to an embracing pose:

I tried something for the first time - posing skeletons before working up the sculpt in ZBrush. To pose the skeletons I used the animation software 3ds max. I took photos of the models in a T-pose and sized the bones to match each model.

Then the bones were rotated into position.This generates an aimation keyframe for each bone. I thought this would be fairly quick, but it turned out to be surprisingly painful! It took me two sessions with the models to get things into a reasonably close match. I think there are some inaccuracies in setting the bone lengths over a photo - even for a T-pose.

Here are a few views of the posed bones:


I then needed to generate a base mesh to sculpt from. So I used ZSpheres positioned on top of the posed skeletons. One could argue why not just pose the ZSpheres and skip posing the skeletons! In fact, having done it, I might argue that myself! :) Actually, one advantage is you can turn on the skeleton beneath the transparent figure forms. If the skeleton was perfectly posed that would be a huge advantage. But there are inaccuracies in the bone lengths and positions and it wasn't nearly as useful as I had hoped.



For the final output I was looking for something geometric. So I used the ZPlugin Decimation Master to experiment with lower and lower polygon counts. This tool lets you preprocess the high resolution mesh and then quickly regenerate lower resolution meshes very rapidly.

These meshes are 6000 polygons total. I really like this look.



Here's the model decimated to 2000 polygons:



Here's the model with 1000 polygons total:



All the way down to 600. Below this level limbs start dropping out :)



Looks like folded paper. That suggests Pepakura Designer. This software takes a SIMPLE (read low polygon count) models and generates a net. A net is an unfolded pattern which can be printed and cut out, then folded back up to create the 3D model. Pepakura generates the fold lines and tabs for gluing.



Sunday, April 12, 2015

Digital Portrait Sculpting - Update

As previously posted - I'm part of a group of sculptors in Ann Arbor, Michigan called the West Huron Sculptors. We share a studio and model time to do figure and portrait sculpting. I've recently revised my workflow - here's an update on what's new.

I was using a Wacom Cintiq display on a mobile stand to sculpt with (picture in use here). I still have that display but I keep it out of the studio now as I'm using a regular Wacom Intuos 3 graphics tablet. I actually prefer this much less expensive method.


The biggest advantage is I can work for 3.5 hours without plugging in. Previously I had to drag an extension cord around the studio as I worked to power the display. Given we have 4 or 5 sculptors working at once this was a hassle. Now I can freely move as I wish without having to tangle with the cord.

We have a rotating model stand. But several sculptors in our group are doing portrait reliefs. This means they generally stay in one spot, or move much less. So rotating the stand adversely affects them.

I was thinking of getting one of the Wacom Cintiq Companion laptops. I'm glad I didn't. Instead I got a Dell XPS laptop. The most amazing part of this machine is the display. It runs at 3200x1800 pixels - unbelievable crisp. Working with this laptop and a standard tablet is really a pleasure.

I also find that keeping my hands on the keyboard is more relaxing than reaching up and always touching the monitor. And of course having my hands away from the screen doesn't block any portion of the image! Finally, since ZBrush makes extensive use of the Shift / Ctrl / Alt keys I always have the left hand available for using keyboard shortcuts to switch tools.


Brushes

I start with a simple base mesh and work it up using a combination of brushes. Here's the base mesh I often start with - you can see there's not much details and a low polygon count:

The choice of which brushes to use in ZBrush is key to efficiently sculpting. Here are the most common ones I work with:



Move Topological: Moves verticies on the mesh around without affecting those not directly attached to the brush area. Coupled with sizing the brush and falloff I use this all the time to adjust the sculpt. For example, using symmetry I can adjust the eye position and spacing very easily.


Clay Buildup: Very useful for building up layers of virtual clay. The alpha channel is used so it gives good control of how the stroke falls off.


Smooth: Takes a rough surface and smooths it out by averaging the level of the surface. I usually turn the intensity way down to make the effect more controllable.


Inflate: Expands an area of the sculpt by pushing verticies along their normals. Great for adding volume to a feature which is too small. It can also be used to deflate - pushing the sculpt in the office direction.


Slash3: This brush is used to cut into a surface to create a tight crease or slash. Great for doing things like folds near the eyes, and edges where the nose meets the face, etc.


Pinch: This brush pulls verticies together effectivly pinching the surface along your stroke. The brush optionally allows the verts to be pulled up or pushed down.


I think it's interesting to note that, with the exception of Clay Buildup, these are the tools available in Sculptris (the simpler, free version of ZBrush).


Remeshing

The introduction of a feature called ZRemesher is a huge workflow enhancement. This feature let's you regenerate the topology (flow the polygons and their density) of the mesh automatically. It does a pretty amazing job and gives you good control over the mesh density. Being able to polypaint the areas where you want higher or lower resolution to the mesh is helpful. I paint out the eyes, ears, nose and mouth in red. After remeshing these area have twice as high a number of verticies than the rest of the mesh which allows extra detail to be added in those key areas.


Materials

You can assign different materials, or shaders, to the sculpt to visualize it in various ways. For example with more reflection to see the smoothness of surfaces, or with harsh lighting to emphasize the edge. My favorite materials are:

MatCap Perl
This is the main material I use when sculpting. Enough highlights to visualize the curvature of the surfaces, but still diffuse enough to see overall forms rather than specular reflections.

MatCap Skin4
Similar to the material above but with a terracotta hue which is nice.

Fresnel Overlay
The specular highlights on this glossy material can really highlight imperfections in the surface as you rotate the model.

Chalk
This provides a very subtle shading with no reflective highlights

Skin Shade4
Another nice variation with low glossiness - this reminds me of working in porcelain.

Outline
This is useful for studying the edges of surfaces.


There are also many metallic shaders which provide interesting effects:

ReflectedMat2




Relief Sculpts

I've been interested in making relief sculptures from the 3D model. This is done by scaling along one axis only. Here's a side view. The scaling here has to happen in stages because the distance from the shoulder to the center-line of the head is great and a compression that fully brought that down to a relief scale would all but erase the details of the face. Therefore the side of the head has to be scaled down, then the shoulder has to be scaled down on its own. Then some simple cleanup has to be done to smooth the intersection between the two differently scaled sections.

Here's the finished piece, printed on a 100 micron PLA printer at Thingsmiths. The cost was $74. I made the frame from Honduras Mahogany:

Another relief, framed in African Mahogany:

Here is a 3/4 view that is scaled down. 
  

The interesting thing about doing this is that the model can have features behind the front face of the sculpt - for example the model's left ear is visible if the relief is viewed from the side. This is fairly common in high relief work in stone. Undercuts like that wouldn't work in bronze work which is cast.

It should be noted that this scaling technique is not at all suitable for very low relief sculpting - for example in making coins. In those cases the artist is not sculpting form, but rather light and shadow. The effect is achieved via the appearance of shadows, rather than by sculpting forms which produce those shadows.


Wednesday, March 18, 2015

Wood Basics


This post contains information on wood, the different species, its structure, different figures, and its use as a material for construction.

Wood Species

There are over 100,000 different species of wood. Some species are full size trees and others are from small woody shrubs. In common commercial use there are dozens of species harvested in the United States and many more from around the world.


Hardwood and Softwood

Trees are divided into two classes: Hardwoods and Softwoods. The hardwoods such as Oak, Poplar, and Maple have broad leaves. In general softwoods, such as Pine and Fir, originate from cone-bearing trees. Hardwoods come from trees that have their seeds contained in a seed-case.

Hardwood and softwood do not specifically refer to how hard the wood is. For example Balsa is a hardwood and yet is very soft.

The Structure of Wood

Wood can be thought of as a collection of drinking straws - where each straw is one of the fibers of the wood. These straws run along the axis of the tree, that is up the length of the tree or along its branches. These straws are what carry the sap of the tree which supplies nutrients to the tree between the leaves and the ground. The straws are the fibers of the wood and a view of them on edge is the what makes the grain of the wood.


The grain direction is along the fibers of the wood:

Grain Direction

As a way to refer to the faces of a milled board woodworkers often use the terms Face Grain,
Side Grain, and End Grain. These are shown below:

Figure

Figure refers to the appearance of wood on its face grain surface (what we think of as the face of the board). The figure can range from subtle to spectacular. Species which are sought after for the figure include, Maple (Curly, Birdseye), Lacewood, White Oak (Quartersawn) and many others.

Subtle Figure - Holly:

Highly Figured - Curly Maple:

Birdseye Maple: 

Quilted, Birdseye Maple:

Fiddle back:

Quartersawn Pine:

Quartersawn White Oak:

Quartersawn Zebrawood:

This image shows how Quartersawn boards are cut from a tree:


As you look at the end grain of the board you can see why the face grain runs in straight parallel lines - the growth rings meet the edge face of the board nearly perpendicular to it:


Heartwood / Sapwood

Sapwood is the living, outermost portion of a branch, while heartwood is the no longer active, inner wood, which often makes up the majority of a branches' cross-section.

This sapwood is where water and dissolved nutrients (minerals) are moved between the roots and the leaves of the tree. In the outer growth rings of a tree (those closes to the bark - away from the center) sap flows through the "straws" of the wood.

Often the sapwood is a different color than the heartwood. In most species, the sapwood is lighter than the heartwood.

An exception to the sapwood being lighter is Sycamore. Its sapwood is darker than the heartwood.


How Wood is Measured and Sold

Lumber is often priced by a quantity known as a board foot. 

Board Foot

A board foot is a measure of volume. The proportions of the wood doesn't matter - only the space it occupies. A single board foot (1 BDFT or BF) is equivalent to a piece 12" x 12" x 1". That's 144 cubic inches of wood (12 x 12 x 1 = 144). A board that is 2' long, 3" wide, and 2" thick is also one board foot - that's the same volume  (24 x 3 x 2 = 144 cubic inches). Two board feet (2 BDFT) could be, for example, 12" x  6" x 4".

4/4, 5/4, 6/4, 8/4, 12/4, 16/4

Wood is normally sold using its thickness as a measure. You'll hear people discuss "four quarter", "eight quarter", etc. This refers to the thickness of the wood in the rough. For example 4/4 ("four quarter") is 4/4 of 1" thick, or 1". But that is not a usable dimension. The wood is in the rough, sawn right out of the tree, and not yet surfaced. That is, it has not been planed (run through a machine which flattens and smooths the face). Nor has it been jointed (run across a machine which flattens and straightens an edge). Once planing has been performed, the wood is thinner than 4/4. It is normal to assume that if you want a 1" finished size you'll need to buy 5/4. After planing it'll be a full 1" thick. 4/4 wood is usually about 3/4" thick after planing.

It is hard to come by wood thicker than 16/4. In fact for many species it is hard to even get 8/4 material. Here you can see a list of species available form one source in Michigan: Armstrong Millworks. Note how few species are available in 16/4 or even 12/4.

Premium for Larger Sizes

Often wood is sold at a premium price for wider or longer boards. That is, even though the volume is greater for these boards, there is an additional charge per board foot for them. That's because it is harder to come by wider or longer boards. And therefore the sellers is justified in upping the price.


Gluing Wood

There is a lot of information about successfully gluing wood. In this post I'll provide a summary of some of the most important considerations.

Glue

There are many types of wood glue. For simplicity I'll focus on one manufacturer - Titebond. The company make a number of different varieties based on the conditions of the wood and the eventual use of the object you are gluing. For example they make a waterproof variety for outdoor use. You can use the Glue Product Selector on their main page for selection help. For typical indoor use, a good choice is Titebond I.

Applying Glue

Manufacturers recommend applying glue to both surfaces that are to be glued. This ensures that each gets "wet" with glue and there aren't any dry spots which don't get enough glue.

Timing is also very important in glue ups. The "open time" for a glue varies. For Titebond Original it is about 10-15 minutes. If you need a bit more open time you can use Titebond III, then you'll be in the 15-20 minute range. After that time the glue is already curing and is difficult to push joints together, or the glue will not develop it's full strength.

Temperature is also a consideration. Gluing in too hot or too cold a setting is a problem - particularly having the glue cure in cold conditions. You should strive to keep the temperature of the material and glue at 50 degrees or above. If the glue cures in colder conditions it will not develop its full strength.

Grain Direction in Glue Ups

It is imperative you respect grain direction when you assemble a project made from wood.
The important consideration is to refrain from a cross-grain glue up. When you glue wood together edge to edge the grain of the pieces should be running in the same direction.

Here's a clear example of what goes wrong when you glue wood without respect to the grain direction. This is one of the first pieces of furniture I made - a small Shaker bedside table. What a sloppy drawer fit! But it gets worse.

The table top has breadboard ends. These are meant to hide the end grain of the top when seen from the side. I naively simply glued them bread board edges on, which is a worst case situation of a cross grain glue-up. 

The wood expands or contracts in width whereas the edge pieces do not expand in width. Something has to give and the top cracks. 


This photo was taken in winter, when the heat is on, and thus the relative humidity is low, so the wood has contracted. But it is locked in place by the side pieces and thus cracks develop as it shrinks. In the summer these cracks close up and are nearly invisible.

The International Wood Collectors Society

I am a lifetime member of the International Wood Collectors Society. This is a group of people who have a passion for working with wood, its identification, and collecting samples.
I have about 220 species in my collection. The standard sample size our members collect is 6" x 3" x 1/2".