A book from the 1930s; a well trusted source for beginners getting started with perspective. I took a few notes whenever I felt pertinent:
Perspective is what makes a drawing appear as a solid object.
The vanishing point is where "the rails of the tracks" meet.
The horizon is the height of your eyes, no matter where you are above the ground.
This book often uses bricks to represent perspective and explain examples. I suppose it's fitting of the time period, but I definitely don't have any bricks lying around.
Is a crucial concept to keep in mind when focusing on drawing in perspective.
One's eye level aligns with the horizon - whether you can see the horizon or not.
the horizon is a straight line across your drawing
If you are inside, you create your own horizon - this is the eye level - an imaginary mark that surrounds your scene.
"/the eye level is level with the eye/"
if you change your eye level - the drawing will change - sometimes entirely.
Eye level determines what we look up to and what we look down at.
The eye-level line is the first line we location in making a perspective drawing.
Parallel Lines & The Picture plane
A group of parallel lines in a perspective drawing, if extending, meet at the same point.
When we face the vanishing point we have one point perspective.
You can have parallel lines that don't vanish (don't have a vanishing point) but that is because they are parallel to the picture plane.
The picture plane is a mental model for imagining how something one is seeing can be conveyed with perspective in a drawing. If one imagines a piece of glass held in front of a scene it can illuminate the perspective as it will be transcribed into a 2d form.
Don't put your vanishing points too close; it will warp your perspective.
"Whoever can draw bricks can draw a city."
Sizing elements relative to structures in perspective is challenging. Perspective Made Easy recommends marking where your figure should be, drawing a line to the opposing vanishing point, up to your height line, and finally a line back to just above your X you marked.
Similarly, provided you have an eye level line and another person in your scene already you can also place an
x where you might like a figure, and extend the lines from their feet and head to each vanishing point. Then it is possible to discern the height of a figure further or closer in depth than the original.
Center of Interest
Be wary of including too much area in a drawing.
If you extend your drawing too close to a vanishing point (or beyond it, even) it will look skewed and distorted.
"Remember that the two vanishing points will not allow you to make a panorama drawing."
A group of roofs usually have the same slope
Imagine a vertical horizon lines that intersects with one of your vanishing points
Most roofs (with buildings facing the same way) will align with the "vanishing point" on your "vertical horizon line" that intersects your actual vanishing point.
You may have to draw diagonals on the building itself, so you can find the center point (if your roof is centered exactly in the middle of the building.)
Drawing the inside of a room
A room is essentially the inside of a box (the "back walls" of the box)
Draw a box and connect the inner lines to the vanishing point,
the contents of the room in two point perspective (ie, furniture) can, of course, be placed in any direction. However, their vanishing points should all come together at the eye-level line.
Drawing two lines across the corners of a square ( a "brick" ) gives you the intersectional diagonals, which are extremely useful for placing items in the center, or relative to the center of something on the brick.
Looking at any circle from the side - it appears elliptical; ie, circles drawing in perspective become ellipses.
Adding windows to a building:
Diagonals are very useful
you can determine where a root reaches it's apex
you can use it to determine where windows and doors, general shapes are spaced out on the upright faces of shapes in perspective;
Shade, shadows, and reflections
"The simple rule for shade is to darken the part of the object that is facing away from the light source."
Representing shade becomes more complex as the complexity of the object drawn increases.
The shape of a shadow depends on three things:
the direction of the sun / light source.
The position of the object depicted
the shapes of the area on which the shadow falls.
Shadows follow the rules of perspective.
The shaded side of an object still has reflected light appearing on it (from the surface where the shadow lies)
This usually accounts for a "dark edge", at least on curved surfaces.
Generally, representing shadows can be quite difficult; they are complex and not always easily solved using mechanical methods.
With reflections, any object mirrored/reflected is left-handed and upside-down.
"if an object isli fted above a reflecting surface its reflection sinks an equal distance below the surface."
When drawing in perspective with up/down hill lines, you will create a second, false eye-level for the hill.
This false eye level has another "vanishing" point where just the hill converges, while other immediate structures vanish as per the actual eye-level's vanishing point.