3d cad modelling types
Post on 18-Jul-2016
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technical department - boclair academy
HeadingThe development of 3D modelling software enables architects and design engineers to create realistic 3D models of their designs.
Previously they would have been built from clay, card or polystyrene blocks.
A 3D computer model is a virtual object which can be rotated on screen and viewed from any angle.
technical department - boclair academy
The wireframe model is built
up using a series of
connected lines to
produce a 3D object.
technical department - boclair academy
The surface model is built up by drawing the surfaces of an object. Like
adding the canvass onto the frame of a
tent.
technical department - boclair academy
The solid model is built up by using simple geometric
forms or extrusions - such as cuboids, cylinders & prisms.
These can be added or
subtracted to produce complex
3D models.
technical department - boclair academy
Can be produced very quickly.
Can be modified very easily.
Easily add colour & surface texture.
Test structural designs before building eg bridges & skyscrapers.
Easily sent by email to remote locations throughout the world.
Less storage space required than a ‘real’ model.
Used to create realistic simulations.
Clients can explore virtual ‘walk through’ of 3D model designs.
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Computer generated models are virtual and can lack the feel of a traditional model which can
be picked up and handled.
Purchase cost of computers and software.
Training of staff in use of software.
Maintenance of IT systems & network servers.
technical department - boclair academy
Y axis+1
-1
-Z-1
Back Clipping Plane z=-1Front Clipping Plane
y=z
y=-z3-D Extension of 2-D Cohen-Sutherland Algorithm,
Outcode of six bits. A bit is true (1) when theappropriate condition is satisfied
Bit 1 - Point is above view volume y > -zBit 2 - Point is below view volume y < zBit 3 - Point is right of view volume x > -zBit 4 - Point is left of view volume x < zBit 5 - Point is behind view volume z < -1Bit 6 - Point is in front of view volume z > zmin
3D Cohen-Sutherland Algorithm
technical department - boclair academy
• A line is trivially accepted if both endpoints have a code of all zeros.
• A line is trivially rejected if the bit-by-bit logical AND of the codes is not all zeros.
• Otherwise Calculate intersections.
On the y = z plane from parametric equation of the line:y0 + t( y - y ) = z + t( z - z0)
Solve for t and calculate x and y. Already know z = y
3D Cohen-Sutherland Algorithm
technical department - boclair academy
3D Cohen-Sutherland Algorithm
• If t not between [0, 1], then the intersection in not between P0 and P1– t = (z0-y0)/[(y1 – y0)-(z1-z0)]
• If t between [0, 1], then use t to find x and y– x = x0 + [(x1 – x0)(z0-y0)]/[(y1-y0)-(z1-z0)]– y = y0 + [(y1 – y0)(z0-y0)]/[(y1-y0)-(z1-z0)]
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