There are many ways that artist use to create the illusion of depth in their paintings
• linear perspective
• aerial perspective
• contrast of values
One that I use most often is the angle and plane concept.
The change of value on a flat horizontal plane is different than that on an inclined plane. To make a plane in your painting appear to be horizontal, the amount of change of value needs to be within a 10 percent range. More of a change will make the plane inclined.
In this demonstration painting, the flat rock surface is basically a horizontal plane. The change of value from front to back is within the 10 percent range and therefore the plane appears to be horizontal.
Step 1 of the painting is the critical step which establishes the change of value of the horizontal plane.
Step 2-adding the background.
Step 3 -adding the details.
Adding more contrast and details in the foreground helps create the illusion of depth.