Drawing sad faces involve knowing what part of the facial features are stressed and pulled. The eyes can be closed or not depending on the amount of grief.
It is a combination of stressed eyes and stretched mouth positions that gives way to a sad expression.
This digital art lesson is in two parts. First, we are going to create a simple caricature of the sad emotions we want to create. Then, we will use it as a guideline and fill in the shadows, values, and light sources to create the face we want.
Use large details brushes for larger shade values and smaller digital brushes for the details. A universal brush I like to use is the chalk brush. It gives enough texture as well as angular elements to give a sense of depth with every stroke.
Are you ready?
We will start drawing sad faces with the front view. The front will give you twice as much practice because you are dealing with a symmetrical drawing. You should be familiar with your digital brushes to start learning these expressions as I rather teach you to focus on what is important rather than teaching you what brushes to use.
Besides, that is what other previous lessons on this site is for!
First, we will need to focus on the eyes. The eyebrows are usually squished in and create a small arc. The eyes are droopy with wrinkles near the outer parts of the eyes and near the center of the nose bridge.

As we are exaggerating this initial expression, the mouth is wide open and stressed. The key here is stretching out the upper portion of the lips and creating an arc at the bottom portions of the lips.
Depending on how wide your mouth is, you may need to show some teeth. As well, make sure the cheeks connect to the bottom of the chin as it stretches downwards. Try to keep the eyes as closed as possible.
Once you are familiar with drawing sad faces from the front view, it's a good idea to continue on to the partial side view. This angle helps you look at how the features twist and fold as you move the face away from its symmetrical axis.
What you need to be aware of is how the eyebrows, mouth, nose, cheeks, and chin begin to angle towards one side. As such, this will not be a perfect reflection of one side of the face versus the other. Rather, you are taking the shapes and are starting to indent it ways that will show off the partial side profile.

For example, instead of being an oval for the mouth, you are looking at one side being rounded while the other side shows a slight indent inwards. This applies to the cheek bones too as it stretches downwards into the chin.
Eyebrows are always stressed, the mouth is stretched, and the chin is protruding upwards. Focus on lighting and shadows to help you out with this step and to use your original caricature for guidance should you feel lost.
Drawing sad faces in the profile view means you need to be mostly concerned with the lower portions of the face. Except for a shorter length, the eyebrows remain the same. It is still stressed and pushed inwards.
Leading towards the bottom half of the face, the cheeks are what is going to be the most predominant feature. Use a light brush and paint a wavy line from the corner of the eyes to the bottom of the chin. Be aware that the cheeks will cover a portion of the nostrils.
As for the upper portion of the lips, it is angling slightly inwards do to the natural stretching as a result of saddened expressions. Draw it accordingly. For the bottom half of the lips, it needs to be protruding forwards because it needs to cover the central bottom teeth with its arching up motion.

As for the chin, point it upwards. You want to show that there are muscles supporting the bottom lips as it covers the teeth.
Overall, this profile view is the view that takes into account all the changes in the face. It can be difficult to draw at first, but as long as you keep breaking down the features and studying it, it will become easier.
Once you understand what constitute a sad expression, you can begin to paint your own variations. As long as you keep in mind how the eyes are stretched and how the mouth is pulled, it is easy to sketch something up.
Remember that the upper lips protrude inwards while the bottom lips protrude outwards from the muscles of the chin.
Some variations to think about are closed eyes versus opened eyes, closed mouths versus open mouths, and flared nostrils versus subtle nostrils.

These will help you generate your degree of sadness. Also, don't forget about wrinkles on the face. Depending on how hard you want the lines to be, you can create a sense of age and gender in your sketch.
Don't forget about perspective either! It can add more depth to your digital painting or drawing.
Go ahead and play with the expressions till you are fully comfortable with drawing sad faces. But above all, keep practicing as much as possible to improve your basic artistic foundations!
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