Rendering Reflective Chrome:

Reflective surfaces like chromium-plated objects can be some of the most complex objects to render. Every square inch of surface is reflecting some part of the environment the object sits in and the reflections distort and wrap to follow the object's form. You'd need a very clear picture in your mind of what kind of environment this object sits in, which is why rendering a test sphere will help you considerably with this.

1. The detail you can put into a reflective surface could be endless. Looking at the above photo reference, there's a lot of detail for one object. So it's important to consider how much you want the viewer to focus on your reflection in the end result. Since the chrome surfaces on the plasma gun are pretty small and cylindrical, the background I'm chosen to use for the reflection is only a sky gradient and a brown/orange ground gradient with a few dark lines running across it for minimal detail. Backgrounds with a straight, flat horizon line are the easiest to paint into reflections by far.

2. The placement of the horizon line on your sphere is also important as it is dependant on whether the viewer is looking at the object from above or below. If the object is at eye level, the horizon line runs straight across the diameter of the sphere. If seen from above, the horizon line curls around the sphere with the edges curling towards the top of the sphere. If seen from below, these edges curl towards the bottom of the sphere. This curling effect will eventually form a circle in the very centre of the sphere when the viewer is directly above or below the object.

NOTE: The balance of sky and ground visible on the sphere is always 50/50 in any viewing angle.

3. With the right horizon line position chosen for your test sphere, you can starting rendering it towards it's chrome appearance. The darkening of the ground and the lightening of the sky as shown on the background example are rendered, followed by the three horizontal lines which are distorted by curling around the sphere.

The hilights are added next. Looking at the photo reference above, you'll notice that the shadows on a reflective surface are practically non-existant. The hilights, however, are very visible because they're the reflections of the lightsources themselves. As a result, the hilights convey every characteristic of the appearance of lightsources, such as shape, edge-sharpness and brightness. A slight halo of colour can still be painted around each hilight as the surface of chrome won't be flawlessly smooth and the slightest amount of bumpiness will reflect some of the hilight.

4. Now begin painting the chrome objects themselves. Start by painting the ground and sky reflections first. As with the last two tutorials, look which directions the surface of your test sphere faces to catch the reflection of the horizon line and see which surfaces on your objects face that same direction.

5. Then block any reflections made by other objects in the scene. This is probably the hardest part of rendering chrome, as there can be a lot of objects reflected in the one surface, and there's distortions to consider as well. To explain how to calculate the reflections properly would be nothing short of a physics lecture, so the best way I can describe it is this:

Look at one single chrome surface on your object and look for one object it would reflect. Find the definable corners of that object to reflect and imagine a line running from that corner onto the chrome surface and bouncing off directly into your eye. Where on that surface does that line bounce? These three dotted lines indicate where on one chrome surface I think the corners of the metal shell are being reflected.

NOTE: This image on the left as been reworked MANY times, and as a result, doesn't match the examples that follow after it.

 6. Start working in the colours and details on the test sphere into those surfaces.
 7. After those colours are blended together, start stroking in the hilights formed from the metallic details in the layer that sits above your linework. In this case, brushing in the pure white hilights formed from the grooves and slits in the gun-barrels really gives the surface it's chromium appearance.
 8. As with the basic metal surface in the last tutorial, these surfaces need scratches and dents worked into them as well. These dents can be rendered the same way, but any surfaces on them that face the white hilights have to be pure white. Also, you can consider the fact that stainless steel surfaces have numerous tiny scratches that only show up as tiny white strokes in the areas close to the white hilight.
9. Just as a quick touch, choose your linework layer and brush a darker colour into the areas where the linework is lighter than the paint below it.
 10. Finally, you can add a halo effect to the hilights of the chrome to define their brightness. These can just be brushstrokes on a new layer with a Gaussian Blur filter applied to them.

11. Phew, well that's it. 3 different surface types rendered in the one scene. To turn these renderings into a finished painting, I've rendered in a desert background at night-time (since there's little ambient light) which is also faintly lit by the same lightsources. The gradients of colour used to indicate the lightsources at the start of this tutorial proved to be useful as flare effects as well, so I changed their layer modes to screen and placed them over the background painting layer.

I hope these tutorials have been useful for you!

Shading Basic Metal Surfaces