[OpenSCAD] Semantics CSG ops with respect to color, materials

MichaelAtOz oz.at.michael at gmail.com
Sat May 30 02:17:08 EDT 2015

Some notes:

a. Terminology

Seems the terms heterogeneous object for one material/colour and graded
material object or composite material object are the terms for mixed output
(e.g. concurrent extrusion via one nozzle) that I have seen in academic

b. This is what Slic3r produces when merging two .STLs to .AMF (collapsed)


c. OpenSCAD export to .AMF has an extra char at EOL


d. Multiple concurrent extrusion is supported in reprap  Firmware

The particular code is  here
<https://github.com/dc42/RepRapFirmware/blob/master/GCodes.cpp#L375>  ,
basically uses multiple floats added to G1 for other extruders. 

Still looking into other firmwares.

I'm still tracing multiple *concurrent* extrusion support in slicers and
CAD/CAM tools.

d. Multiple extruders supported:

Slic3r: many extruders (I stopped at 17), either loading an .AMF (with
material id defined - needing support in OpenSCAD etc), or via building an
.AMF (material id is set sequentially from 0 for each .STL loaded), or using
different extruders for perimeter/infill/support/interface (which doesn't
needs support in CAD/CAM - ie OpenSCAD))

Simplify3D: 6 extruders, outline, infill, support. Seems to only support two
colour by loading 2 .STLs.

CuraEngine: 16 extruders. Either load an .AMF which sets extruder number for
the volume, or load multiple .STLs and assign an extruder to each. Does not
seem to have the option to set different extruders for infill, support etc.

Repetier Host seems to work well for both Slic3r and CuraEngine for multi

e. Some examples of multi-material printing

REPRAP (Meddel?) Continuously variable 2 colour Blue/White

LulzBot Taz3  FlexiDuelie (std extruder & FlexiExtruder)
(Part1 intro ABS & NinjaFlex but not as a composite)
(Part2 Alien Hand - interesting design evolution)

Voxel8 Multi-Material 3D Printer - print plastic and conductive ink and add
imbeded parts

f. What Blender does:


object has multiple material(s) (a default and optional others)
material has a colour
mesh has multiple material(s)
mesh has face(s) (and edges & vertices)
face (part of the mesh that reflects colour)
face has a material, default material is assigned on creation.


Node(s) can define mixed materials, with a factor (0-1) defining the blend.
Node can have a texture map influencing the blend.

material can be linked to an object or to a mesh. ("Short explanation: If 
connected to the object, you can have several instances of the same obData 
using different materials. If linked to mesh data, you can’t")

Object Render Format (menu). This menu has four options which define how the 
object is to be rendered:
Surface - Material applied to object planes.
Wire    - Material applied to wires following the object edges
Volume  - Material applied to the object volume.
Halos   - Material applied to halos around each object vertex. (??)

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