design and communicaton graphs-perspective projection

gadgetfreak

Can anyone tell me the construction for Perspective Projection?? its really infuriating me not being able to do it!!:mad:

HughOS

How to do it?

1) Set up your picture plane. (In plan, bring the two widest points back to the spectator, bisect the angle between and draw a line perpendicular to the bisector through the point nearest to the spectator.)

2) The picture plane is the view that you'll be looking at. So once you have it in plan as a line, you'll need to project it perpendicularly to see the shape of it. (Basically, in plan do sliding set squares to bring the line that is the picture plane up, like your drawing an auxiliary at the angle of the p.p. The new line is the ground line. The question will give you the height that the horizon line is above the ground line so draw another construction line at that height above the new ground line.)

3) Next you need to find your vanishing points. The object you're looking at will appear to vanish on the horizon, therefore parallel to your vision it the line along which it will vanish. (Go to plan and draw a line straight up from the spectator and straight across from the spectator until you hit the line that is the picture plane. Take the points where it hits up to your projected picture plane and where they hit the horizon line are the two vanishing points.)

4) It's easier to find all the points separately as you are drawing the shape of the solid, otherwise you'll just end up with a lot of confusing lines. In plan
take the points that you want to draw back to the spectator, where they hit the line that is the p.p. is where you need to take them up.

Is this sounding really confusing? I think I'd be confused if I had to read it. Here's an example from the Junior Cert, after you've found the vanishing points and the heights.

http://www.practicalstudent.com/subjects/tg/exampapers/pages/hl2005saq10.html

Just click 'Show answer'. If you want me to finish off explaining then just say so.

timmywex

Some Very Cruel Children Punched George Hughes Very Hard

S.V.C.C.P.G.H.V.H

S=Spectator
V=Vanishing lines
C=Cone of vision
C=Centre Of vision
P=Picture plane
G=ground line
H=horizon line
V=vanishing points
H=height lines


Thats the method i use!