What are some techniques to give drawings 3D appearance?

Question

I am very new to this world of graphics design. I have noticed that some drawing look 3D but I have no clue what's making them perceived like that. For example how can I turn a circle to look like a sphere, etc.

As an example, why does the left drawing look flat but the right one looks 3D?

Could you please suggest some "rules of thumb" techniques to make objects look 3D using 2D vector graphics? or at least some references to get started.

P.S: It would be really nice to suggest that only for Inkscape so I can start practicing.

Edit:

Please kindly don't suggest Adobe products nor any non-FLOSS (Free& Libre Open Source Software) products.

Many thanks

Answer 1

I would give you 1 word, but this word turns into another word later.

1. Shadow

I will not use your basketball. I need to simplify this further.

A. No shadow does not give you any 3-dimensional clue.

B. But adding shadows gives you visual parameters on things that are in front.

C. Or behind.

But it also gives you references to distances. D, E, F.

There are different types of shadows.

G. Cast shadows, parallel shadows.

H. Perspective shadows.

In the end, these two types of shadows give you a clue on what is the relation between the object and the background. The first tells you the background is parallel to the circle, and the second one tells you that the circle is perpendicular to the circle.

I. But there are also shadows self-projected in the object, which gives you the internal shapes of the object.

And here is when I want to switch the word shadow for a specific tool you can use.

2. Gradients.

Different types of gradients will give you a thing on what is the 3D shape of the 2D figure

J. It could be a sphere

K. A cone

L. The top view of a helix

M, N. If you start combining gradients you now start having different materials.

O. You can make more complex things. But in the end, the thing that gives you shape is the shadow (gradients).

Explore more about materials here.

Sure, there are other elements like perspective and size.

But the look that a gradient, when used as a shadow, is the main factor.

P. A flat shadow does not look 3D at all

Q. A cube with some perspective

R. With some gradients

A Bonus, Blending modes.

A quick way to apply a shadow on an object, but maintain the editability of both, the shadow and the main shape, is the multiply blending mode.

S. No blending mode

T. Multiply

U. One over the other

You could explore more ways to combine them.

U. No blending mode

V. Add blending mode

W. Here is another thing. One shape inside the other. In order to really control the shape of my sphere, I in reality put the gradient inside a circle.

One important thing about shadows is directionality. For example in photography, the angle in where you put the light makes a portrait flat or dimensional.

So, keep exploring.

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In Inkscape, you have a couple of tools that can help you to make gradients.

Although my interface is in Spanish, the location and icons are the same in English.

1. One is the gradient fill tool and the other is the grid fill. (The names might be different, feel free to correct me) Just select an object and apply a fill.

2. Open the object panel so you can control the exact color of the fill.

3. A fill is handled by nodes. Use the node editor to edit a specific node (4) and change its values on the object panel (5).

The Mesh fill works similar to the gradient fill, but you have different nodes on the outer rim of the object.

Look for tutorials on how to use nodes and fills. For example https://www.google.com/search?q=inkscape+gradients

And here is a blur tool

P.S. As you first asked about "the theory" I only illustrated the point with "X" program, it does not matter which one. The only gradient I think you do not have on Inkscape is (L) The last images are done in Inkscape.

On Inkscape, I do not use any filter on the filters tab. I am only using in these images gradients blur and blending modes. It is not about having a ton of tools, but only a few and controlling them.

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Some other tools to explore

Perspective

1. Make, for example, a text.

2. Convert it to path (Path>Object to path)

3. Make a shape with the desired perspective.

4. CLick the "no longer text", click the domain

5. Extensions >Modify Path> Perspective.

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Extrude

1. Select two simple paths

2. Extensions > Generate from Path > Extrude

Answer 2

Your leftmost version could be an image of a basketball. It's round, it has curves which look distorted like they were on a sphere and the main colors orange and black are also common. The curves are narrow, the one which is seen nearly sideways should be narrower, but the error is difficult to see.

The image looks flat because

• it has not the shadow that common lightning creates,
• there's no gloss that light often makes if the material is not full matt and
• the nearest black curves are not at all wider than the more distant ones. As well we could say that it's drawn without perspective.

The glosses are optional, because the material really can be matt. And the perspective can as well left out. It becomes then like its photographed from far away with a tele lens. But the shadow is important. If the light comes more from somewhere above the object and less from the sides, the shading could be this:

In the left there's your original (clipped from your attachment, edges made sharp). In the middle there's an as big circle filled with a radial gradient from white to grey. In the right the gradient shape is placed on the original with blending mode = multiply.

How I decided the somehow not fully wrong gradient? I guessed it. I have drawn hundreds of spheres and seen drawings of spheres even more. Inkscape in addition allows experimenting. 100 attempts cost only some time. Drawing with real paints needs better knowledge before making a stroke.

The easiest way to improve the drawing is to add a faint gloss which can be seen in the brightest place of your rightmost version. The 2nd trick would be to have some environment. If it's on the floor it should make a shadow, for example. And a well drawn player under the basket definitely would make nearly any circle a ball.

As said gradients are tricky and more complex shapes need also more complex shading. Gradient meshes can be used. Also blurred shapes can make the trick acceptably. It's an alternative way to make gradually changing colors, brightnesses and opacities (=the same which is done by using gradient fills) An example:

The grey shape leaves free those areas of the underlying ball that are assumed to get light directly from the midpoint of the ceiling lamp. The border of the light and shadow is tried to be drawn well, elsewhere the shape is much larges and very coarse.

In the right the shape has got blending mode Multiply and a hefty Blur.

In the next image the blurred grey shape is clipped with a circle to fade the extras. The blurred shape is also rasterized because the gradients in Inkscape do not obey perfectly the clipping path. I can live with it, but it's harmful.

Do not clip nor rasterize it before you have seen it makes a good shading. You can well edit it also as blurred with the node tool. Here's a version where the border of direct light from the lamp midpoint is drawn with more care (=more elliptical) and the grey is made darker:

As you see I only darkened the orange.It cannot be made brighter in the strongest light area because it's already as bright maximally colorful orange as RGB system can make.

Here's another case where blurring has been used instead of gradients: How to create a cylindrical circle in gimp

The used program doesn't have gradients along nor across paths like illustrator has. Blurring is used as a workaround.

Other sources:

Watch Youtube tutorials and repeat the shown tricks. Search for old Loomis books. Check for ex. this one https://archive.org/details/andrewloomiscreative.illustration/Andrew%20Loomis%20-%20Successful%20Drawing/page/n93/mode/2up

The link leads to one book of Andrew Loomis and opens the chapter which tells about light.

BTW. The book is full of useful stuff of drawing; see for ex how to get the perspective look right, but it actually wasn't a big problem in the basketball image. ADD: Your question is extended later to contain it as well.

One can wonder what the hell a book of pencil drawing does in modern days and computer software. Believe, the behaviour of light should be taken into the account in all imaging as well with pencils and paints as with more limited drawing tools, like Inkscape.

I like limited drawing tools because they prevent my clunky hands to make too many errors and destroy valuable artwork materials. Just for me the limitations - for ex. it's much easier to draw a straight line than a curve with full of irregular twists - are a plus. A talented and skilled pencil user probably cannot tolerate them.

As a bonus I get some crutches to draw easily smooth curves, uniform colored surfaces, gradients, tiled patterns of shapes, some textures, some widely used regular 2D shapes, even 2D projections of a limited number of preset 3D shapes, like boxes or other polyhedrons. But Inkscape still is only a drawing tool, it doesn't at all help to select the curves, polygons and colors which together are the image which presents a scene. One must decide them between his ears like with any other drawing tool.

Answer 3

It is called shading, sometimes also lighting or lighting and shading. Basically light reflects less back from a light source the further away you are form the light normal. How do you do this? Well you have to start by imagning where the light is situated. Theres no rule where you put it you just make a decission and keep it in mind while your doing the drawing.

Image 1: First you arbitrarily decide what point the light is over

Obviously this is easy for a sphere, since there is only one point that can be the center more complex objects have several. The rule of thumb is you need to think about the shapes as combination of simpler shapes and figure where that may be. If you figure out wrong the image will look wrong.

OK, the light now falls off from this point and gets progressively darker the further you get. You will learn how this falloff happens by observing real objects, thats the rule of thumb explanation. The real explanation is very technical and would take a few hundred pages.

So how do you get the light to fall of in inkscape? Well vector applications don't exactly have dedicated tools for this, so you need to resort to experimantation. But they do have roughly speaking 3 tools that can make graduated surfaces:

1. Gradients
2. Gradient meshes
3. By creating a lot of objects by interpolating the shape.

Again there's no dedicated rule off thumb you use what you have available and fudge it out. For a sphere you can use a radial gradient fill centered on the light normal location. Its not entirely accurate but good enough for quick illusions.

Image 2: Falloff done with radial gradient

You can then use several gradients and pieces of gradients for more complex objects. There is no single way to do this since there is no dedicated tool set for this.

Next lesson how to make shadows , after that how to make reflections.