SLIDE 1
Using Exis)ng Geometry
- 1. Snap to it
- Trace edges (object snaps)
- Use it in Boolean Opera*ons
- 2. Use it as profile or path for other opera)ons
- Extrude door/window trim
- Sweep picture frames
2: Deriva*ve Geometry Using Exis)ng Geometry 1. Snap to it Trace - - PowerPoint PPT Presentation
2: Deriva*ve Geometry Using Exis)ng Geometry 1. Snap to it Trace - - PowerPoint PPT Presentation
2: Deriva*ve Geometry Using Exis)ng Geometry 1. Snap to it Trace edges (object snaps) Use it in Boolean Opera*ons 2. Use it as profile or path for other opera)ons Extrude door/window trim Sweep picture frames 3D shapes, 2D
SLIDE 2
SLIDE 3
3D shapes, 2D “sec)ons”
- Extrusion
– Sec*on & displacement
- Revolu*on
– Sec*on, Axis & angle
- Sweep (1 rail or 2)
– Sec*on & path
- LoMing
– Mul*ple sec*ons (aka contours!)
SLIDE 4
Boolean Opera)ons
- Requires “solids” (Rhino “polysurfaces”)
– “Closed” or “water-*ght” – Consistently oriented (surface normals) – Passes “Euler” tests
- No dangling edges
- No shared points (touching corners)
- No shared edges (touching edges)
SLIDE 5
Boolean Opera)ons
- Difference
– Subtract one volume from another
- Union
– Combine one volume with another
SLIDE 6
Building Details: openings
Cut an Opening using Booleans
- “subtract” punched window openings
- “remove” front & back door-ways
- “add” decks and flooring where needed
Trim the Opening sweeps and extrusions If repeated, use blocks.
SLIDE 7
Building Details: trim
Building door & window trim #1
- Trace edges, snapping to opening vertexes
- Offset inward.
- Extrude (&cap) inner and outer edges.
Building door & window trim #2
- Trace edges to provide “rail” for sweep
- Draw cross-sec*on at rail-head
- Sweep cross-sec*on on rail
SLIDE 8
Building Details: glazing
Fixed glazing #1
- Define 1 plane of glass within wall for all
windows in that wall.
SLIDE 9
Smooth-shading face\ed geometry
SLIDE 10
What about curved surfaces?
Not all “surfaces” are planar surfaces! So …
- Figure out how to model and render curved
surfaces (very hard), or
- Approximate curved forms with many
polygons and figure out how make them look smooth (“smoothing”)
SLIDE 11
What about curved surfaces?
- Not all “surfaces” are planar surfaces! So …
- Approximate curved forms with many polys?
– Slows all opera*ons – Turns out to be difficult due to human vision
- Render tessellated surfaces to look smooth?
– Called “smoothing”
- Many versions, including “Gouraud” and “Phong”
- Implemented in OpenGL
SLIDE 12
Smoothing Tessellated Models
SLIDE 13
128 polygons vs. 11,680 polygons
SLIDE 14