Perspective is very complicated topic even when we try to handle a single perspective grid. It gets even harder when you try to make the scene more dynamic by adding more objects and rotating them. And when you want to connect two dynamic objects with an elastic tube, like a neck... that's hell!
Luckily, on a small scale we can safely simplify perspective rules. In some cases, we can even totally forget about them and let Photoshop do the trick. That's what I'm going to show you in this short tutorial—how to outsmart perspective and make Adobe Photoshop draw necks, tails, snakes, and other twisted tubes for you.
Warning: the tool we're going to use is available in CS5 and higher.
1. Create a Base
Create a New File (Control-N) with 600 px Width and Height. Select the Ellipse Tool (it's hidden under the rectangle), hold Shift and draw a circle.
Duplicate (Control-J) the circle. Press Control-U and drag the Lightness to the right to make the upper circle white.
Make the upper circle smaller with the Free Transform Tool (Control-T). Hold Shift and Alt to keep the proportions and position.
Press Control-Alt-G to clip the dot to the big circle. From now on put all the new layers between them.
Select the Pen Tool (P). Change the settings as shown below:
Create a New Layer (Control-Shift-Alt-N). With the Pen Tool still active, click the white dot, hold Shift, and click somewhere higher up. The line will be drawn.
Repeat the previous step for other directions, with various bright colors.
Create a New Layer below the lines. Use the Rectangle Tool (U) to draw a gray rectangle on the lit side.
Draw more rectangles, gradually brighter, to shade the sphere.
Merge (Control-E) all the gray rectangles (if they were separate). Go to Filter > Blur > Gaussian Blur and use any Radius you like to blend it.
Merge (Control-E) all the layers belonging to the black circle. Then use the Free Transform Tool (Control-T) to make the circle smaller.
2. Load the Mixer Brush
Find the Mixer Brush Tool—it's hidden under the classic Brush Tool.
Change its preset to Dry, Heavy Load. If Sample All Layers is checked, deselect it.
The Mixer Brush Tool uses the same brush list as the classic one. Select the Hard Round brush and resize it to fit the circle inside. Hold Alt and press firmly to get the sample.
Let's make it smoother. Go to brush settings (F5) and drag Spacing to the minimum.
That's much better!
3. Draw Long Tubes in Perspective
I guess there's not much I can explain now! You're probably already feeling how powerful this trick is. Depending on the direction of your stroke, a different side of the circle will be visible. And since every stroke is made of dozens of them, real "sides" are being created.
This is like painting in 3D!
You need be aware, though, that Photoshop won't create soft corners for you. You need to bend the tube yourself, leading the stroke softly in the corners.
If you want a width-variable tube (like a tail, or a whole Eastern dragon), simply check Shape Dynamics and lower Minimum Diameter. Just be careful about the slightest strokes—they may be hard to lead properly.
If you want to save this brush for later use, open Window > Tool Presets and just create a new one.
That Was Magic!
You can use this trick for so many occasions that I'm not even going to limit you with my ideas. You can use it as guide lines for a drawing, and if you shade the base circle properly, it will become a real shaded base for a painting! Hope you found this tutorial informative, and—have fun!