Sculptris

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Draft


1 Introduction

Sculptris is a very easy, yet powerful artistic modeling application. Basically you start from a geometric form (e.g. a ball or whatever and then sculpt/deform with various tool "brushes". E.g. you can crease, grab, draw, flatten, smooth, etc.

Sculptris (alpha aka 1.02) was developed by Tomas Pettersson and will be further developed by Pixologic: “Sculptris has captured the hearts of artists with its fun, intuitive and user-friendly interface - indeed a perfectly sweet companion to our big monster ZBrush! Tomas will be moving to California, from Sweden, to join our team. It is our pleasure to welcome Tomas and we look forward to a fruitful collaboration on future Pixologic projects [...] Pixologic would also like to give you a little appetizer ‘goodie’, an Alpha version of Sculptris for Windows - a unique, very ‘cool’ artistic modeling application still in raw baby stage and now incubating at Pixologic HQ. The current version, formerly known as Sculptris 1.02, will be renamed under Pixologic banner as Sculptris Alpha 5.” (A Gift From Pixologic, 07-23-10, retrieved nov. 18 2010.

Sculptris is based on dynamic tessellation. The word tessellation initially referred splitting (or tiling) a plane into patterns that fill the plane with neither overlaps nor gaps. This concept also can be applied to 3D and tessellation refers to creating a 3D mesh structure made of triangles. See the tour 3D for some pictures.

Often, real-time 3D models by default have a low triangle count in order to gain performance. However, low-triangle count models look quite coarse. Some programs then can subdivide the model into a multiple of triangles in order to give these models a smoother look. The opposite is also true. Models can be made simpler in order to gain performance. Models that are defined by abstract mathematical functions are yet a different case. In order to be rendered by a 3D graphics program, these abstract models can be "triangulated".

Dynamically creating a mesh or adding/removing triangles to/from a mesh is called dynamic tessellation. Sculptris does dynamic localized tessellation, i.e. tessellates the wireframe mesh only where it is needed. Various tessellation algorithms are at work depending on the brush tool and its options.

1.1 Before you start

Print out a good cheat sheet
Basis are *.obj files

With Sculptris you start by working on a simple ball or a plane, but you could import any *.obj file. Make sure that the obj model is centered. You can import more than one model and reposition/rotate these.

Sculptris (as of 2010/early 2011) is alpha software. Therefore save frequently ! !!

Symmetry

By default all operations are symmetrical, i.e. if you pull out something to the "left" it will also pull out to the "right".

You can turn "Symmetry" off if you like. When you turn it on, the object will be symmetrical again.

When you import an *.obj file, symmetry may be off, therefore turn it on if you work on structures like a human.

Brushes and tessellation
  • You can set the "Brush/Tool" Size and Strength with the rules on top middle.
  • However, these don't define how many new triangles will be created when you draw, inflate, grab. etc. This is done with the Detail [Q] slider. For starters keep in the middle. When it is to the left (0), Sculptris will not add any new triangles.
Views
  • mouse-middle to orbit around the object, i.e. rotate it to look at it from a different angle. (So this won't rotate the coordinates of the object, just your view).
  • mouse wheel to zoom in/out and (if necessary)
  • Shift-middle-mouse or ctrl-alt mouse to pan (move it left/right or up/down).
Wireframe and triangles
  • Click on wireframe to see the structure (at least when you feel that Sculptris has trouble or is getting slow). Reduce triangles with Reduced selected tool or the Reduce brush if the program starts being being slow (see also below).

1.2 Basic modeling procedure

(1) Define the very rough shape of the object

  • Use the Grab [G] tool for the very rough work, set the brush size and pull out. Make sure to untick Global and Limit.

(2) Use the Grab tool with limit ticked in order to modify things that stick out.

(3) Use the other various sculpting tools to define the rough shape. E.g. for modelling the face, you mostly would use the draw tool.

1.3 Sculptris for Rapman/RepRap modeling

Sculptris is an interesting tool for modeling objects that then can be printer with low-cost fabbers like the RapMan. Sculptris imports/exports *.obj files. With Meshlab they can easily be translated to *.STL if needed. Skeinforge does import *.obj but I never tried.

Here is a rough outline of the workflow

  • Start either the default globe or with an object that has more or less a flat bottom. If the object is very low poly, subdivide first using the subdivide all tool for example.
  • If you want to speed up g-code generation, reduce the meshes after you are done sculpting.
  • Translate to STL, e.g. with Meshlab
  • Position and repair with Netfabb
  • Translate to g-code and print

2 Presentation of the sculpt tools

2.1 General drawing options

Positive vs. negative effect

  • Selecting a tool with either the left or the right mouse button will produce a default/positive effect or an inverse/negative effect. E.g. the Draw tool will either add volume or carve out volume.

Detail (number of polygons)

  • The user can control how many triangles the brush will add with the detail slider. If the slider is set it to zero (far left), triangles will NOT be added during sculpting. Conversely, if the Detail slider is set to its far right, many triangles will be added.
  • It is a best practice to periodically reduce unneeded polygons. This can help remove unwanted bumps and enhance computer performance. The easiest method is to press Reduce selected button several times. This action will reduce the polygon count of the entire model. Alternatively, the Reduce brush will optimize areas that are brushed over. Drag the brush from the rougher to the complex areas.
  • It is helpful to Toggle the wireframe view [W] on in order to inspect the density of polygons that have been created.

Size

  • Sets the size of the brush.

Strength

  • Sets the strength of the effect. For rough modeling, use the 50% setting.

Background Image

  • A background image may be used for reference. To set a background image select Options > Background > then navigate to desired image. Sculptris accepts either PNG or JPG file formats. Note that the image stretches with the program window.
  • Sculptris remembers the last background image used. When opening a new file, the previous background image will persist. To restore the default background image, select Options > Background > then navigate to the Sculptris program file on your drive. Select Data > background.png.

2.2 The draw brush

The Draw brush is the most important brush once the basic structure has been established. Unlike other tools you can use it a few times over the same spot. This is not recommended for the inflate tool.

Options
  • Clay: Recommended to paint layers upon layers (like you would do with clay)
  • Soft: Produces more rounded edges

2.3 Crease

The Crease tool is the opposite of the Pinch tool. It allows you to create indents in the mesh.

2.4 Flatten

This tool has several purposes:

  • It is used to reduce areas. Use low to medium strength
  • Is also can be used to make areas more regular.
Options
  • Lock plane will sample the orientation at first contact and then create a flat surface around that has the same orientation. This also means that with this option on, this brush can add materials
  • Angle falloff: Tries to keep near-by planes more intact. I.e. when you flatten a plane, it will not flatten bumps nearby.

2.5 Pinch

Will sharpen an existing corner, i.e. one that you created with a combination of draw and flatten

2.6 Smooth

The Smooth tool burnishes surfaces and edges. At high strength settings, it can be used as an erase tool. Unlike the Flatten tool, the Smooth tool keeps the overall rounded form of the geometry.

2.7 Inflate

Inflate is somehow an alternative to the draw tool. Make sure to use it slowly. This tool can both be used on surfaces, edges, tentacles.

  • Pull something out (creating new triangles)
  • Create overhangs

Note: If you want to pull out a lot of volume, do not use this tool, use grab instead.

2.8 Grab

By default (options off), drag will drag the selected area (brush size) in a given direction. This is most radical tool for creating tentacles and similar shapes. Once you created a tentacle, the use inflate to make it thicker.

Options
  • Limit: Works like the default grab, but the result is much less radical. Allows to drag the selected area into a direction. E.g. you may pull up the corners of a mouth made with draw in order to have your character smile.
  • Global: If global is on then you can move around separate objects in your scene. You can have separate objects when you load in *.obj models. If you want two balls, then turn symmetry off, move the ball to the right and then turn symmetry on again.

2.9 Scale

Can adjust proportions of selected areas (smaller or bigger)

Options
  • XYZ: changes sizes proportionally
  • Global: can change the size of an entire object

2.10 Rotate

Allows to rotate an area. First provides a starting point and an angle. Once you move out of the circle you then can rotate.

Options
  • Global: will rotate a whole object

2.11 Mask

You can define an non-editable area of an object.

Select the "Mask" tool ("M" icon) or use CTRL (Command on MAC) to access the Mask function when another tool is active.

To reduce the masked area, select the "Mask" tool, click on "Invert (X)" and brush an object's mask.

Un-mask the whole object: CTRL-Click-Drag Background.

Invert mask: CTRL-I or CTRL + Click background.

Note that masking can increase geometry to help with smoother transitions when editing a selected area. To control geometry, use the Detail and Strength sliders.

3 Links

3.1 Download

Version 1.02 aka Alpha 5

3.2 Tutorials and Manuals

Propaganda videos
Training videos
Good training videos are not too easy to find.
Others (but these are too fast for beginners)
Specialized stuff

3.3 Shared models

Base models
  • Three simple (not so good) models can be found in the models folder of Sculptris
Other

3.4 Other information

3.5 Support