ASVAB CampHidden Edges and Occlusion flashcards
8 cards with the formulas, rules and traps from this lesson. Answer in your head, then flip to check.
Term · 1/8
What is occlusion?
A closer opaque surface blocking the view of part of an object behind it. The rear object is unchanged; a missing line in the picture does not mean a missing piece.
Rule · 2/8
In a view, what does "in front" mean?
Closer to the observer along the viewing direction, not higher on the page. Use the viewing arrow or stated layer order; viewing from the opposite side can reverse which part hides the other.
Rule · 3/8
Line-of-sight test: how do you decide if a point is visible?
Imagine a straight ray from the eye to the point. If it hits a closer opaque surface first, the point is hidden; if nothing closer blocks it, the point is visible.
Fact · 4/8
Does a partly covered rod or curve change shape behind the cover?
No. Occlusion hides, it does not remove material. A straight line stays straight, a diagonal's two exposed tails keep the same slope, a curve stays smooth and a hidden tip stays pointed.
Common trap · 5/8
Is a dashed line drawn across the opaque cover a correct normal front view?
No. Dashed hidden lines are a drafting convention for showing concealed edges. An ordinary visible-surface view shows nothing of the rear object inside the cover unless hidden lines are requested.
Common trap · 6/8
How do you tell true occlusion from a broken-line distractor?
With occlusion the exposed rear stroke ends exactly at the cover's boundary. A stroke that stops short of the cover leaves extra blank space and is wrong. Check both entry and exit points.
Fact · 7/8
What sets how much of a rear line a cover hides?
The actual cover outline where the line crosses it. A circle hides a longer span through its center than near its top; a diamond's sloped edges stop the line, not its bounding rectangle.
Strategy · 8/8
Fast elimination order for occlusion answer choices
Reject in order: wrong cover shape or position, rear line drawn over the cover, a missing exposed tail or arm, then subtle entry and exit mismatches against the source shapes.