Drawing Basics: The picture plane in 1 point persective

Dealing with one point perspective has its challenges. It seems simple enough but we can sometimes run into unforeseen problems. This often happens because we miss some of the specifics about the guides of one point perspective. One example is recognizing the relationship between the front planes or front surfaces in a scene and the picture plane. Its a straightforward guideline but if it is missed the drawing will not come together how we would like.

This posts is going to take a look at the picture plane and positioning of the front surfaces in one point perspective respective to the picture plane. We will discuss the principle and show a simple explanation using an exterior scene. 

If you would like a refresher on one point perspective visit this link. Otherwise, let's get started. 

Picture plane

First, let's establish what is a picture plane as understood within one point perspective. The picture plane is an imaginary plane the runs perpendicular to the viewers line of site. This plane assists us in establishing the viewers frame of reference to the scene.

For example, in the image of the house the viewer is looking directly at the front of the house. Looking at the illustration just below the photograph you can see the picture plane illustrated in front of the house. We can consider this an imaginary window that we are look through to see the scene.
Picture and front surfaces

Once we know where the picture plane lies, we can use the one point perspective guides to set up the drawing. First, we are just going to position the front walls of the building in relationship to the picture plane. 

In one point perspective, any front surface plane of a structure will be parallel to the picture plane.   

For example, all the walls (surface planes) that are highlighted in red are facing directly at the viewer. These will run parallel to the picture plane and appear flat to the viewer.
The vertical edges

Why would we pay attention to this detail? If we look at our basic one point perspective diagram we will see that all the front planes of each of the cubes are square.

One thing this tells us is that all of the side edges of each cube are perpendicular to the horizon line, running straight up and down.

Looking at the house, the sides of the house do the same thing. (The house is basically a combination of boxes) 
The same guide applies to the vertical edges within the front walls of the house. Notice that the edges of the windows and door run 90 degrees from the horizon line.
Horizontal edges

Since the front surface plane of a cube is square that also tells us that the top and bottom edges of the front of the cube run parallel to the horizon line.

Looking at the diagram of the house, we can see that we would draw the house in the same way. All of the top and bottom edges run parallel to the horizon line.

Combining the understanding of the path the vertical and horizontal edges move gives us an understanding of what needs to be done to illustrate the front surface planes to appear parallel to the picture plane in our drawings. 

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