Case in point, when painting rock formations, hilltops, mountain ridges, the beginners often copy the shapes without understanding the structure of the lines. It is not unusual for a range to look like a row of staples or horseshoes. I have sat in on classes where the instructor is unable to convey the concept of "contour" lines.
I am sure most of us have seen and understood what elevation lines represent. When we look at a topography map the elevation lines give us a description of the shape of the land. We know where the ridges and gullies are, and the relative steepness or flatness of the land. In painting a mountain range, we are just tilting the map on its side, so the elevation becomes not the height from the horizontal plane, but the distance to where we stand.
To illustrate my point, I've chiseled out a wooden block into the shape of
a mountain range. Now I have painted the " contour lines " on this block, and these lines describe the shape of the mountain ( as elevation lines describe the heights at different points on the map). When we paint these contour lines in succession, we are in effect transcribing the mountain range.
I have sliced through this block of wood into slabs to illustrate this point. The more slabs I create, the more information I am able to draw ( i.e. more contour lines ), this is akin to having more "pixels", or watching a 1080p HD program vs. the 480 lines old programming. The "chuen" lines that I have discussed in the past i.e. hemp "chuen", is merely a sliver of such a slab; thus showing just a partial contour instead of the entire shape. Therefore one can use a few strategic contour lines to describe the main shape of the range, and the "chuen" or "texture rubbing" lines to describe the minute details of the topography.
As we paint the lines with the Chinese brush, we are naturally in a "center tip" form as we traverse horizontally on paper, and as we turn the corner onto the vertical lines, the natural angle of inclination puts the brush in a "side-tip" mode automatically. That part of the line describes "thickness" of the slab that we are painting, thus unknowingly giving a 3 dimensional appearance to what we have painted.
Hopefully these little hints will help us attain a better understanding of Chinese landscape paintings.