Sunday, July 5, 2015

CNC Routing a ZBrush Sculpt

I made use of the Roland 4-axis router at the Penny W. Stamps School of Art & Design to make a walnut version of a portrait sculpture I created in ZBrush.

Here's the ZBrush sculpt (more details on its creation are available here). It has been decimated down to about 400,000 polygons to make is manageable for RhinoCAM (the software used to drive the router).


Mounted in the bed of the router is the block of walnut. It is about 3" x 4.5" x 8". It is clamped by the 4th axis at one end and by the tail-stock at the other end.


Roughing begins using a 3/8" diameter 2 flute end mill. This is pretty rough yet only 0.05" was left for the finishing pass.


The 4th axis of the router is rotated to the other side and roughing continues.


The first finish pass is done using a 1/8" ball end mill. It is cutting from the face to the back of the head.


Here's the final finish pass using a 1/16" diameter ball end bit. Only in the smallest crevices was any material removed.


Here's the part after the router has finished: 


Here's are a few clips of the routing process. This is shown at the actual speed of the router:



After routing there's still a need for hand work. Some sections of tear out need to be sanded/scraped out (above the left eye, at the base of the neck). The back of the ears had some very strange tool marks that needed to be filled (I used a mix of sawdust and polyurethane). And the area where the block was attached needed to be carved away and finished to match the curvature of the head and texture of the hair.





With some finish and a base:





Thursday, July 2, 2015

Walnut Torus Knot Table


I made another Torus Knot Table. This time from air-dried Walnut.


 Detail of the part connections:


Made from 30 parts which dovetail together end-to-end:


Here are the parts as generated by a script:


Here's a video of removing the finished part from the fixture after cutting:

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

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 digital 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.

PLA 3D print:

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.