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Scene & Group Manipulation

As with generators, look at the exemplars under Exhibition or the worked examples under Tutorials to see these commands used correctly.

Instance​

instance name object
    [rotate (rx ry rz)(degrees)] [scale (sx sy sz)] [translate (tx ty tz)]
    [surface surface_id] [LOD LOD_type] [shading shading_type]
endinstance

Creates an instance of geometry. One can optionally rotate, scale, translate the instance and specify its color, level-of-detail (LOD), and rendering mode.

  • object: the name of the primitive, generator, or group that will be instantiated.
  • rotate: draws a vector from the origin to the point specified in (rx ry rz) and rotates over that axis (degrees).
  • scale: scales the shape in each included axis by the multiplier given. Ex: scale (1 3 0) will retain the x-axis size, multiply the y-axis size by 3 times, and flattens the z-axis completely.
  • translate: moves shape along the coordinate axes by the given number of units. An instance can be translated, rotated, etc. multiple times within the same line: JIPCAD will execute these commands left to right.
  • surface_id: a specified surface color, given as an RGB fraction from 0 to 1. When multiple surface colors are given for a generator--such as a sphere within a nested groups--JIPCAD will use the first ("deepest") color defined. For example, RGB (25.6 204.8 0) is equivalent to surface G color (0.1 0.8 0) endsurface.
  • LOD_type: defined types:
    • NOME_OFF: not rendered
    • NOME_BOUND: render only the bounding box of this subtree
    • NOME_EDGES: render this subtree in wireframe mode
    • NOME_FULL: fully render this subtree
  • shading_type: defined types:
    • NOME_INHERIT: Shade this node in the same style as its parent
    • NOME_WIRE: render as a wireframe
    • NOME_FLAT: render with flat shading: one color per polygon
    • NOME_GOURAUD: render with Gouraud shading; interpolate vertex colors across each polygon
    • NOME_PHONG: render with Phong shading; interpolate vertex normals across each polygon and recompute lighting at each pixel

Group​

group id
    instance id1 object_id1 [instance_parameters] endinstance
    ...
    instance idN object_idN [instance_parameters] endinstance
endgroup

Defines a collection of instances of primitive objects or other groups. Groups are the most general construct to introduce hierarchy into a model description.

  • id: the name of the instance.
  • object_id: the name of the object to be instantiated.
  • [instance_parameters]: all the optional parameters discussed above.

Note that creating a group does not display the objects instanced inside of it. Another instance statement must be added for the group in order to include it in the scene.

Subdivision​

subdivision id
    [sd_type sd_flag]
    sd_level
    instance id1 object_id1 [xform & color] endinstance
    ...
    instance idN object_idN [xform & color] endinstance
endsubdivision

Subdivides a merged mesh into smaller facets. (Alternatively, can perform subdivision in the GUI: Edit >> Subdivide.)

  • sd_flag: the type of subdivision algorithm used.
  • NOME_SD_CatmullClark: the plain and simple CC subdivision
  • NOME_SD_CC_sharp: CC subdivision respecting “sharp” flags in the mesh.
  • sd_level: the integer number of iterated subdivision steps.
  • [xform & color]: the optional parameters relating to transformations and coloring.

Offset​

offset id
    [offset_type offset_flag]
    height
    width
    instance id1 object_id1 [xform & color] endinstance
    ...
    instance idN object_idN [xform & color] endinstance
endoffset

Thickens a surface mesh of zero thickness into a thicker B-rep that can be 3D-printed.

  • offset_flag: the type of thickened surface generated:
    • NOME_OFFSET_DEFAULT: This offsets the starting mesh inward and outward symmetrically. Each facet in the original mesh maps to two facets in the offset mesh; one of them with reversed orientation. Each boundary edge of an open polyhedron will map to a quadrilateral facet.
    • NOME_OFFSET_GRID: The edges of the starting mesh are viewed as thin wires which are then thickened into 4-sided prism segments. This is different from “gridding” the original mesh, where the openings in each facet are a given fraction of the facet geometry.
  • height: the half-thickness of the generated surface normal to the original facets.
  • width: the width of the prismatic beams in the tangential direction of each facet.
  • [xform & color]: the optional parameters relating to transformations and coloring.