Construction Lines Explained – What Line Should I Draw First?
Every perspective contains 5 different types of construction lines. Each type of line is used for a specific purpose and is best applied at a specific point in the drawing process. The order in which you draw your construction lines is important, but as you’ll see, you have some flexibility in determining the sequence you use. Here’s a brief description of each type of construction line and advice as to when to insert them into your drawing:
Category #1:
All the lines in category #1 originate at the SP and extend to the corners of each object shown in plan. These lines must be in place before any vertical lines (i.e. category #4 lines) can be drawn.
Category #2:
All the lines in this category are anchored to key points on objects shown in elevation or side view and projected horizontally into perspective space. These lines must be in place before convergent lines (i.e. category #5 lines) are added to your perspective.
Category #3:
Lines in this category are used exclusively to determine the location of a drawing’s vanishing points. Locating the vanishing point in a single point perspective is relatively easy and uncomplicated since you only have to draw one vertical construction line between the SP and the Horizon Line. Two point perspective on the other hand are a bit more complicated. They require two lines on each side of the SP (i.e. one pair of lines to locate the VP on the left and one pair of lines for the vanishing point on the right). All Category #3 lines must be in place before any convergent lines (i.e. Category #5 lines) can be added to your perspective.
Category #4:
In this category, vertical lines descend from the PP into perspective space. The vertical lines start where the diagonal lines stretching between the SP and the Object intersect the Picture Plane. Vertical lines can only be drawn after the diagonal lines from category #2 have been added to your drawing.
Category #5:
This group of lines converge on vanishing points. They originate at the intersection of horizontal and vertical construction lines located in perspective space. Convergent lines can only be drawn after the vanishing points have been established and one or more pairs of horizontal and vertical lines have been joined together.
