Sketch is the foundation of plastic arts.
Pay attention to the shape of the pen when drawing, and fully consider the boundaries between light and shade, reflection and gray surface.
To have a strong sense of volume, we must learn to summarize the relationship between faces.
Generally, fruits are at least divided into left, right, top and bottom, and there is a part in the middle.
Under a certain light source, the brightness in all directions is different.
The brightness of two adjacent faces is also different, or they are flat.
If you practice more, your lines will be better. See the picture book for details. If the fruit is only a small detail in the painting, don't paint it in depth.
As long as the big relationship mainly shows the theme.
If it is a single fruit, what matters is the dividing line between light and shade of the fruit.
As you said, if you want to draw a head, you must have drawn plaster geometry.
Right? Pay attention to the three-dimensional effect when making fruit. Consider it a plaster.
Geometry, such as apples, is like a sphere and mangoes are like a cylinder.
When drawing geometry, remember the dividing line between light and dark to draw the three-dimensional sense of the object.
As for the cable you mentioned, the geometry corresponding to this object is different.
Don't have too many lines on the same floor to brush too deep at a time when one direction can't be adjusted. On multiple floors, the lines on the same floor should be drawn in one direction and cannot be confused. We should carefully observe the changes of light and shade. If you really can't see it, you can take a picture with your camera and draw it. If we can't master the basic skills well, we can't do it. Work hard!