Chapter 2 : The Points

Question 1

How are points in space denoted ?
Horizontal projection notation ?
Vertical projection notation ?

Answer 1

A,B,C
a,b,c
a’,b’,c’

Question 2

Where are projections of a point always situated ?

Answer 2

Both projections (horizontal and vertical) of a point are always situated on straight lines perpendicular to the axis and intersecting the axis at one and the same point.

Question 3

What is the unfolding orientation of the HP ?

Answer 3

Clockwise unfolding

Question 4

A point in space is in the I quadrant. When are its horizontal and vertical projection on an orthographic drawing ?
II quadrant ?
III quadrant ?
IV quadrant ?

Answer 4

• First Quadrant: HP below OX, VP above OX
• Second Quadrant: HP above OX, VP above OX
• Third Quadrant: HP above OX, VP below OX
• Fourth Quadrant: HP below OX, VP below OX

Question 5

Where do we find the vertical projection of any point on HP ?

Answer 5

On coordinate axis.

Question 6

Where do we find the horizontal projection of any point on VP ?

Answer 6

On coordinate axis

Question 7

Where is the point if both its projections lie on the coordinate axis ?

Answer 7

On the coordinate axis.

Question 8

What is the distance y from the horizontal projection of a point to the coordinate axis equal to ?

Answer 8

It’s equal to the distance from the point to VP.

Question 9

What is the distance z from the Vertical projection of a point to the coordinate axis equal to ?

Answer 9

It’s equal to the distance from the point to HP.

Question 10

When is z positive ?
When is y positive ?

Answer 10

z>0 for all points above HP
z<0 for all points below HP

y>0 for all points in front of VP
y<0 for all points behind VP

Question 11

What is the meaning of “Given a point in space” ?

Answer 11

The expression “Given: a point in space” means that a specific point is defined by its coordinates in 3D space, and this point is being used as a reference for further analysis or projection onto the planes.