January 2014 Video Tutorial : Drawing Plastic and Chrome What's the Diff?

[Barbara B]

Drawing Chrome & Plastic: What’s the Diff?



A lot of Xara artists (especially Ron Duke, our Featured Artist!) like to draw shiny, complex, reflective shapes. So what is that shape made out of so it reflects? Plastic? Chrome? Swiss cheese? This month Gary takes you into both a physics lesson and an artistic workout as you learn how to draw stuff that looks like plastic and other stuff that looks metallic.

Nuances are everything in the competitive field of art. And face, it: you really want to learn how to draw chrome! C’mon along!

Watch the video and get the resource files.

Then show us some shiny stuff in this thread!

[angelize]

I really like this month's subject I've always had a hard time capturing that very shiny metal look without resorting to live effects. So here is an attempt at a metal ball. I'm not sure I have the look quite right.

[Gare]

You did good, Frances, especially considering I forgot to give away a still image of the "softbox" lighting on a metallic sphere.

Suggestion here: don't reflexively put a highlight in front of the ball at 11 o'clock when the reflections of your room don't indicate there's a light in that location. And the highlight should be less fuzzy around the edges. Highlights and reflection need to work together when illustrating metal. If the metal shows a blurry reflection, the specular highlight must be soft, too, and vice versa.

It's impossible to make out, but the soft room model has four bare lightbulbs on the ceiling, and that's where the hot spot (highlight) is reflecting from. Also, it might be nice in an illustration to capture the wall behind the camera, or black space as a photographer's studio would look, and perhaps even a camera and a photographer in thje reflection to add photorealism.

Because I'd like this month's tutorial to be larger than "how to draw a chrome sphere", attached are four more images with a big thumbnail below (a toenail?). I created a 3D squiggle and I'd like everyone to check out the distortions on the surface when put in the softbox room which the checkered floor.



Frances, you drew the floor and the walls quite well, congratulations! It's great when members improvise.

My Best,

Gary

[alanstancliff]

An interesting tutorial, Gary.

Quick question (I think). You did an excellent job of explaining the difference between the plastic ball and chrome ball reflection. But what about the floating crystal ball? How does that differ from the chrome ball? Instead of reflection, it would have diffraction (if I got the technical term correct).

Regards,
Alan

[Gare]

I’m sorry, Alan, but your quick question necessitates a less-than-simple answer.

First, there is no “instead” when describing the light-bouncing characteristics of objects we see in real life, and then attempt to draw. A crystal ball, as per your example, lets a high degree of light through it, reflecting only a small percentage of available light in the scene.

Now, I did not want to get into how to illustrate glass, or other semi-transparent object this month—or probably any month—because it’s a study in physics and light, and not a Xara tutorial, as pedestrian an excuse as that might sound! Glass is a phenomenally complex material because it both passes light through it, and it bounces light back at the viewer.

Just about all materials we see on and through real world objects have one or more of three common attributes: Diffuse, ambient, and reflective lighting, the last of which is described by a highlight and a coherent direct reflection. If you assigned these properties a percentage, almost all real world objects would have a sum of 1.0 total lighting. So most materials can be described by %Diffuse, %Ambient, and %Reflective lighting.

Transparency is a higher-order of material description: it incorporates %D, %A, and %R, but transparency itself is like “shininess”; shininess gets its characteristic from percentages of material reflectivity but we cannot attribute shininess to a substance’s makeup.

Instead of comparing glass to metallic reflections, Alan, let me try to describe glass characteristics so they are meaningful to an artist, and perhaps our audience here on tg will find it easier in the future to illustrate a wickedly complex surface using Xara.

First of all, glass and other semi-transparent materials refract light, just like plastic tends to do, except, depending on how transparent the glass is, we will see objects through the glass (as with a magnifying glass) “bend” light, and that’s why when viewed straight on, a glass of water with a spoon in it looks as though the stem of the spoon is broken and moved over a little.

How little? It depends on the Index of Refraction of the fluid, and that’s why I didn’t cover this aspect in this month’s tutorial! It’s too science-y and not art-sy enough! I’ve attached and posted two images of a sphere, with a high and a low index of refraction here. The higher an index of refraction, the shinier a material is (air is 1.0 ior, and metal can be as high as 20), and when you tip transparency into the recipe, the higher the ior, the more light is bent as it reflects. And all of this stuff depends on your point of view on the semi-transparent object.

By the way, in the real world, invisibility is not the same as transparency. Glass, for example, can be 99% transparent, and yet it can tint light as we see it, and it can have a specular highlight. The Invisible Man, on the other invisible hand, had no highlights and didn’t bend light as it traveled through him.


When a waterdrop, as another example, is viewed, it appears to magnify what’s under it (like a leaf), and very little light is transmitted through the droplet so the reflection of the leaf on the opposing side is crisp and easy to make out. Specular highlights are particularly evident on waterdrops because there is only one way for the highlight light to exit; toward the viewer, the other side is blocked by the surface. Edges of a waterdrop are dim as light has to travel farther, and at an angle to travel back to the human eye.

Glass can also act as a lens, especially when the surface is curved. So we’d expect to see a bright interior when an artist draws a photorealistic waterdrop or magnifying glass.

Finally, the reason why reflections appear upside-down in glass is because the far side of something such as a crystal ball is convex; it inverts the reflected light, and the near side of the ball lets the lightwaves come back at the observer upside-down. Which is the same visual phenomenon as a spoon or other metallic bowl-shaped object showing you an upside-down reflection. Reflections might be reversed, but specular highlights aren’t, and that’s an important point to keep in mind when you draw this stuff.

I hope this helps, I know it's too long for Twitter (!),and here are two rendered models from two different programs that use a physically-based modeling system, that closely mirrors (pun intended) what we see in the real world.

Thanks to Alvy Smith for putting up with a stranger’s questions, and the advice and some of the PIXAR RenderMan background info.





My Best,

Gary

[wizard509]

Very interesting Gare. The top image looks goofy but shows the principles you describe.

[Gare]

The top image looks awkward because 1.) I spent zero time setting it up, and 2.) Vue doesn't have as good a rendering engine as Luxology modo does.

And there's a 3.)

3.) The viewing angle makes it impossible to tell whether it's transparent or perfectly reflective. The important thing about the top outdoors image is that it shows light accumulating in its shadow, similar to holding a magnifying glass on a piece of wood to do woodburning.

-g

[csehz]

Just about all materials we see on and through real world objects have one or more of three common attributes: Diffuse, ambient, and reflective lighting, the last of which is described by a highlight and a coherent direct reflection. If you assigned these properties a percentage, almost all real world objects would have a sum of 1.0 total lighting. So most materials can be described by %Diffuse, %Ambient, and %Reflective lighting.

Transparency is a higher-order of material description: it incorporates %D, %A, and %R, but transparency itself is like “shininess”; shininess gets its characteristic from percentages of material reflectivity but we cannot attribute shininess to a substance’s makeup.

Gare that is very interesting summary, thanks very much.

Also the tutorial is great, already started but stucked somewhere (concretely was not able to mould? the chess table pattern in the sphere ), but maybe on the weekend will have a chance for a next run on it

[stygg2003]

Well guys this is as far as I've got with the tut. but will have ago at the next stage of inserting the chess floor image into a drawing. If you were drawing a room with walls, ceiling and floor would you see in the chrome drawing the two walls, ceiling and floor plus whatever was facing front on to the sphere? I mean like another wall with a door perhaps ?

Stygg

[csehz]

I also tried today, but the drawing took the control over me and some not existing reflecting material came out



So let's say something abstract That chess table pattern sure mould but still was not able to reproduce that kind of magnify effect to the middle