Understanding Color Relationships

Color theory teaches us about relationships through colors using the wheel. It helps us understand the language structure of colors and supports us when we need to use them.

First, let’s understand what primary, secondary, and tertiary colors are and their relationships. Primary colors differ according to the model we are considering.

Newton was the first researcher who composed a color wheel to understand the relationships between colors, explaining his theories in the treatise “Opticks, or, a Treatise of the Reflections, Refractions, Inflections, and Colours of Light.”¹

We create secondary colors by mixing primaries, and we make tertiary colors by combining a primary with a secondary color. We have 12 colors, of which three are primary, three secondary, and six tertiary.

In addition, there are analogous colors, which are harmonious and close to each other in the wheel. There are also complementary colors, which are contrasting and opposite to each other on the color wheel.

Betty Edwards studies color theory theoretically and develops it from a practical point of view in some books.

For a deeper understanding of the concepts developed in this section about theory and its practical application in painting, it is interesting to read her book Color: A Course in Mastering the Art of Mixing Colors.²

From color theory comes the terms hue, saturation, and value, of extreme importance in defining the properties of a color.

Let’s learn their definitions and main concepts.

Value, Saturation, and Hue

Continuing with the discussion on color theory, we can say that each color has three main properties: value, saturation, and hue.

Blender allows us to control and modify them through the Blender color picker window shown in Figure 5-1.

The HSV panel will enable us to determine the material color’s hue, saturation, and value in Blender. We have the eyedropper and the Alpha value in addition to these tools in the color picker.

We can copy any desired color from the Blender window with the eyedropper. With the Alpha value, we set the transparency. Finally, we can see the effect of the trasparency applied to the object in 3D view only after setting the blend mode to Alpha Blend, Alpha Clip, or Alpha Hashed in the Settings window of the Material panel in the Properties panel.

HSV is the default method in Blender; it is an additive color composition method that considers the perception of hue, saturation, and value.

Let’s see the meaning of these three components and how we can use them in Blender by modifying the Blender color picker.

Let’s move to the Shader Editor and edit the base color of the Principled BSDF shader of the object’s material with the color picker highlighted in Figure 5-2.

The figure shows that we obtain pure black by setting the Hue, Saturation, and Value values to zero. First, let’s describe these three color components.

The value modifies the ratio, or percentage, of black and white.

The value can also be defined as lightness and specifies the amount of white or black in the perceived color, as shown in Figure 5-3. In fact, in the image, we can see that we get the white color by keeping the hue and saturation at 0 and bringing the value to 1.

So, the value is the degree of lightness, or darkness, of the color. In the Blender color picker, if this intensity is 0, no light will be added to the tone, while if this intensity is 1, the color will be visible in all its brightness.

Instead, the Saturation measures the color intensity, as shown in Figure 5-4.

If the saturation value is equal to zero, the color is achromatic.

When bringing the value to one, the color reaches the maximum intensity, as shown in Figure 5-4. Finally, the hue is the pure color. If we set the value and saturation to 1, we can select the colors at their maximum purity by modifying only the hue values rotating in a circle.

These concepts are more easily understood if we look at the simple scheme in Figure 5-5.

Changing the values of the Blender color picker boxes, we see the sliders move according to the white lines highlighted in the figure. So, the value cursor moves on the black-and-white diagram on the right, while saturation and hue go around in the color wheel.

This simple operation allows us to understand the influence of every single component.

Now that we have faced the main concepts of color theory, let’s go on with digital painting and drawing.

Krita

Krita gives us critical help to extend the features of digital painting. We mentioned it in Chapter 4, when we talked about Gimp.

As we already said, the difference between the two pieces of software is that while Gimp is more suitable for image editing, Krita is better for drawing and digital painting.

It’s worth dwelling for a moment on its painting tools that we can use to create textures, painting and sculpting devices, masks, etc.

As we will see in the exercises of this chapter, Blender painting tools, joined to those of Krita, offer us infinite creative possibilities and extend our pictorial possibilities.

Krita allows us to realize painted textures for Blender materials with its numerous brushes. We can implement cartoon, pictorial, or even realistic textures.

As far as digital painting is concerned, Krita is probably the best open source alternative to Photoshop and Gimp, with a wide range of customizable brushes, layering, blending modes, etc.

Moreover, Krita’s interface is more attractive, friendly, and intuitive for digital painting than Gimp’s. In Figure 5-6, we can see the default interface.

As we can see in the image, all the tools for digital painting are in an intuitive interface. If we want to change the interface layout and the tools, we can change the workspace, as in Blender. We click the icon “Choose workspace” in the upper-right corner and choose the favorite workspace in the opening window.

On the other hand, if we want to add some panels or re-add one that we closed by mistake, we click its name in the window that opens from the main menu by selecting Settings ➤ Dockers.

Let’s see some of the tools Krita gives us.

Krita’s Tools, Palettes, and Color Selectors

Brushes are the most exciting tools for us, but before learning about them, let’s briefly mention the devices that help us modify the image data.

In Figure 5-7 we see one above the other; the most important Krita panels are the toolbar, the default palette, the Advanced Color Selector panel, and the Brush Presets panel.

The Krita toolbar contains all the main tools for creating, selecting, and editing graphic objects.

We have five different types of devices.

• The Selection tools allow the selection of parts of the drawing in different ways.

• The Paint tools create various strokes, which we define with a shape, a size, a kind of opacity, and other elements. They depend on the definition of the image.

• The Vector tools do not depend on image definition, but we can modify them using control points like the Bézier curve or freehand path tool.

• The Guide tools are drawing aid tools, such as a grid, perspective, or assistant tool.

• The Transform tools transform objects or layers on the canvas.

Then we have customizable palettes, which allow us to choose the right colors to get the visual impact of the final project. Krita provides some predefined ones and enables us to create customizable ones. A range of colors is grouped according to different logic and the result we want to achieve.

On the other hand, the color selectors are the tools that allow us to choose the color model, depth, and profile. They allow us to select an additive or subtractive color model; a depth of 8, 16, or 32 bits; and different color profiles.

In this chapter’s “Introducing Color Theory” section, we already saw some of these concepts.

The Brush Presets panel contains all the brush tools divided into categories such as Paint, Sketch, Ink, Texture, etc.

The range of tools is comprehensive and customizable in endless ways.

Now let’s see how to use Krita for digital painting.

Krita’s Brush System

Krita contains a palette of predefined brushes, the Brush Presets panel. These brushes are ready to use and were built to demonstrate the different creative possibilities of this software.

They are divided into several categories and are helpful for other modes of use, ranging from digital painting to 3D texturing, pixel art, etc.

We can paint with the brushes by clicking and dragging the left mouse button or, as we will see shortly, with a graphic tablet.

We can modify the size of the brush by pressing Shift+LMB; we can decrease the opacity by pressing I and increase it by pressing O.

We can modify the brush type in the Brush Presets window.

This system of integrated brushes is quite extensive, as we can see in Figure 5-8.

It is just like actual painting or drawing, where we can use many tools: pencils, charcoals, chalks, watercolors, oil painting, etc.

With its numerous tools, Krita imitates the effects of real painting very effectively.

The available tools give us many editing possibilities because each is customizable in the Edit Brush Settings window, which allows us to edit options and create a virtually infinite number of Drawing and Painting tools.

We can open this panel in the toolbar under the main menu with the top-left Edit Brush Settings button, which is framed in white in Figure 5-9.

Many parameters allow us to vary presets in this window, including Size, Rotation, Opacity, etc.

As in the case of Blender brushes, also in Krita, we start from standard models that we can then modify and save for later use. We find the saved tools together with the others in the Brush Presets panel.

As we saw in Chapter 2, in Blender we must distinguish between tools and brushes. The tools are on the toolbar and have general settings; brushes are our tools saved with the customized settings, and we can save them directly in the Edit Brush Settings panel.

Also in Krita, we have the brush tips and the brush presets: the former are the basis for the latter. We can choose and modify primary forms from time to time with all the parameters provided by the Edit Brush Settings window.

It is essential to use a graphic tablet to make the best use of these tools and extend the pictorial or sculptural functions beyond the use of the mouse.

Let’s see how to choose the graphics tablet and set up our work.

Graphics Tablets with and Without Screens

Using a graphics or pen tablet, we can control our brushes and strokes more easily than with a mouse.

For example, we can modify the pressure sensitivity to alter the radius and the strength of the brushes in every painting or sculpting mode.

We can choose a graphics tablet or a drawing tablet with or without a screen.

The graphics tablet is a sensitive surface connected to a computer. In contrast, the drawing tablet with a screen allows us to draw directly on the display. In some ways, a tablet or PC with a touch screen is easier to use than a pen because we can draw by looking simultaneously at the screens.

In other aspects, a graphic tablet without display is more comfortable because it shows the view freely and allows us to work at a certain distance from the screen, as in traditional painting and drawing.

Also, a graphic tablet has a much lower cost. We can use it effectively with Blender and image editing and painting software like Gimp or Krita.

There are many good-quality graphics tablets such as Wacom, Huion, Ugee, etc. They work well and have many functions, including the following:

A graphics tablet is also great to use with the Grease Pencil, the recent Blender painting and animating tool that we, unfortunately, don’t cover in this book.

We prefer the graphics tablet without a screen. We can comfortably use it in Blender Sculpt and Edit mode. Also, it is perfect for experimenting with painting and sculpting in Blender and Krita.

The Graphics Tablet with Blender

First, we prepare the graphics tablet to use with Blender by setting the pen keys and tablet hotkeys for optimal use of our software.

We will give Blender settings for sculpting and painting.

First, we install the software provided with the tablet, open it, and perform the simple operations by setting the interface as shown in Figure 5-10.

Let’s define the functions of the pen’s buttons with the same functionalities as the mouse’s buttons and middle wheel.

So, it is crucial to be able to use the same functions when using the graphic tablet to work efficiently and quickly.

We set the single button of the pen with the middle mouse wheel function to rotate 3D view easily. We can then adjust the pen’s pressure sensitivity according to our needs in the same window. Our graphics tablet has 8,192 levels of pressure sensitivity available, and we can adjust them in the Pressure Sensitivity Adjustment window to match the way we draw.

Instead, in the next window, we can adjust the screen area to the sensor size of the graphics tablet, as shown in Figure 5-11.

Finally, we can customize the Express Keys setting. We define eight hotkeys in the case of our tablet, as shown in Figure 5-12.

Now let’s see the Blender brushes and how we can use them.

Blender’s Painting Brushes

Blender provides us with brushes and chisels and digital tools for sculpting and painting. We have already met Blender’s chisels in Chapter 2. Also, there are other tools for painting in the Texture, Vertex, and Weight Paint modes. Moreover, we have various exciting painting tools in the Draw mode of the Grease Pencil object.

Blender’s tools change in the different object modes. We find the necessary tools in the toolbar on the left of the interface: in Sculpt mode, we have at our disposal instruments to sculpt; in Texture, Vertex, and Weight Paint mode, we have devices to paint.

Instead, the keyboard shortcuts to perform operations usually do not change in the different modes and ways of painting and sculpting. This characteristic of Blender is attractive. If we learn to use one editor’s interface, we also know how to use the others.

This method makes our work much more manageable. Of course, the sculpting brushes will be a bit different from the painting brushes, but the adjustment tools, the keyboard shortcuts, and the graphic tablet settings will be almost always the same.

Painting in Blender

We deal first with Texture Paint, then with Vertex Paint, and finally with Weight Paint.

Each of these systems has a dedicated Object mode.

We can set them in the Object Interaction mode of the 3D view header, as shown in Figure 5-13.

We’ve already looked at modes in Chapter 1. So now, let’s quickly review them, distinguishing between those for three-dimensional modeling and those for painting.

The first three object modes in the list are for modeling.

In this first section, we talked about color theory and digital painting with Blender and Krita; then, we presented the painting modes in Blender.

We will study the various creative possibilities and tools available in these different modes.

Let’s start with the Texture Paint mode.

The Paint Mask and Face Selection Masking

This device is the fastest but is less complex than the ones we will see next. It is available in the 3D view header in Texture Paint, Vertex Paint, and Weight Paint modes.

It allows us to draw only the portions we want to modify and mask where we don’t want to paint.

We select the object to paint, go to Edit mode, and select the faces to paint on.

Let’s go to Texture Paint mode and choose the Paint Mask button in the 3D view header. We can see the button highlighted in white in Figure 5-25.

From now on, we can paint only on the parts we have previously selected in Edit mode.

We can paint with a brush or use the Fill tool from the toolbar to evenly fill all the selected parts.

Afterward, if we want to smooth the line between two colors, we can turn off the paint mask and use the instrument Smear.

Now let’s see a different, more sophisticated method to mask the texture with a stencil.

Create a Stencil

Painting with stencils can add intricate details to our textures effortlessly. With this method, we can create any image in our favorite image editor and then use it inside Blender as a mask to paint our surfaces, as practiced in the Teapot_Stencil file attached to this book.

Let’s see how to do it in a brief exercise:

1. 1.

   Select the object to paint, create a material, and add a base texture.

    
2. 2.

   Make the UV unwrapping, and then move to the Texture Paint workspace.

    
3. 3.

   Create a black-and-white image in Krita or Gimp or another image editor. Keep in mind that when you use the texture in Blender, the white will be transparent and the black will be opaque, so you will paint with the white strokes.

    
4. 4.

   In the Texture Properties tab of the Properties Editor, add a New texture by clicking the New button shown in Figure 5-26. Call it Stencil.

    

1. 5.

   Then with the Open button, load the image previously created with Krita, as shown in Figure 5-27.

    

1. 6.

   You can see the texture loaded in the texture window in the Properties Editor’s Active Tool and Workspace Settings panel. In the same window, change the brush mapping from Tiled to Stencil.

   When you move with the cursor in 3D view using the Image Editor, you can see the stencil in the window, as shown in Figure 5-28.

    

To work profitably, we need to know how to use some controls. Let’s see them.

We can move the stencil by clicking the right mouse button (RMB) and dragging the mouse. To change the mask size, we click with Shift+RMB and drag. To rotate, we click and drag with Ctrl+RMB. Then we paint with the brush Draw. So, the white parts are transparent, and the black portions mask the brush strokes.

Reset Tiled instead of Stencil in the Properties Editor’s Active Tool and Workspace Settings panel to return to normal painting mode.

We have just created a custom mask on which we can paint with different colors, and with the same method, with Krita, we can create an infinite number of patterns.

Now we see another masking system that makes a different result.

Painting with a Mask

This masking system is different from the previous one.

Also, with this method, we can create an image inside or outside Blender and then use it inside Blender to paint our surfaces.

But while the black parts hide the brush in the first example, the white portions paint on the object’s surface in this one.

Let’s see how to do that with another quick exercise.

1. 1.

   In Blender, create a material connecting two different materials based on Principled BSDS shaders with a Mix Shader node and call it Mask.

   You can use any material; for example, you can use metal and overlay rust or scratches.

    
2. 2.

   Then create an Image Texture node and add a new image by clicking the button New, keep the default settings but change the width and height to 4096 x 4096, and rename the image Mask. Then connect the Color output of the Image Texture node with the Fac (that is the factor input) input of the Mix Shader node, as shown in Figure 5-29.

    

1. 3.

   Now go to the Texture Paint workspace, change the viewport shading to Rendered, and in the Texture Properties tab of the Properties Editor, choose Brush Mask on the menu that opens; then click New, as in Figure 5-30.

    

Choose one of the procedural textures in the Type menu, such as clouds or marble, etc. Now you can paint directly on the object in 3D view or the texture in the Image Editor. Where you paint, the underlying material appears.

1. 4.

   Then, to improve texture distribution in the Texture Mask window of the Active Tool and Workspace Settings panel of the Properties Editor, change Mask Mapping from Tiled to Random. Next, select the option Random and increase Jitter in the Stroke section, as shown in Figure 5-31.

    

If we want more control over the brush marks, we can create a more defined image in an external editor and add it to the already made brush mask.

Now we can paint with an image we created instead of using the procedural textures produced by Blender.

There is an example in the Teapot_Mask.blend file that comes with the book.

After this long introduction on Texture Paint, we will learn about two more of Blender’s painting modes in the next section. Instead of operating on a texture, we work on vertices and weight in these two modes. So, we don’t modify the colors of the image we are painting on. Instead, we will paint the vertices of an object and assign a weight to each vertex. In this way, we control the distribution of many effects of various kinds, as we will see in the following two sections.

Now we study Vertex Paint mode where we can paint the vertices of our objects.

Unwrapping the Mesh

We start doing the UV unwrapping of the mesh. In this way, we obtain the two-dimensional development of the three-dimensional object’s form.

Now we can correctly apply the texture to the object.

Creating and Painting the Texture

Now that we have developed the object’s shape on a two-dimensional surface, we can quickly paint on the thing or apply the texture through the material. Let’s paint first.

1. 1.

   Select the teapot. Click Texture Paint on the Topbar and go to the Texture Paint workspace.

    
2. 2.

   Go to the Properties Editor’s Active Tool and Workspace Settings panel. Here, in the Texture Slots panel, create a new texture by clicking the + Add a Texture Paint Slot button in the white highlighted rectangle in Figure 5-39. Next, choose the Base Color channel.

    

In the window that opens, name your texture CeramicBaseColor, give it a white color, and set the dimensions to 4096 x 4096 pixels. Click OK to confirm.

To conclude the example, let’s see how to paint only some object parts with Paint Masking. We talked about different masks in the “Painting with a Mask” section of this chapter.

In this exercise, we will use the method to paint only on the selected portions. It’s quick and easy.

1. 1.

   To enable face selection masking, move to Edit mode and select the faces you want to paint.

    
2. 2.

   Then we go back to Texture Paint mode and click the Paint Mask button in the 3D viewport header between Texture Paint and View, highlighted in Figure 5-40.

    

To activate and deactivate this masking system, click the Face Select button.

The masking doesn’t work with the button deactivated, so we can paint the whole object and not only the parts selected in Edit mode.

In the next exercise, we will apply the second painting method we talked about and make a UV map of an object in Blender.

Introducing the Add Texture Paint Slots

In Exercise 10, we have already seen how to make a Base Color texture in the Texture Slots window.

From the Texture Slots window in the Texture Paint workspace of the Properties Editor, we can add the paintable textures for different channels of the Principled BSDF shader directly in Blender, as shown in Figure 5-43.

When adding a texture from this box, Blender connects it to the dedicated shader’s inputs and automatically adds the nodes needed to join it correctly.

Now let’s see how to create layers in the Blender Image Editor.

Understanding Layers in Blender 3.0

The Blender Image Editor still lacks a layer system such as Gimp, Krita, or Photoshop.

This exercise will create three layers to modify light and shadow in Blender, directly manipulating textures without using the 3D view lights.

To do this, we must follow these steps:

1. 1.

   Open the file Teapot.

    
2. 2.

   Assign a material to the teapot.

    
3. 3.

   Then go to the Texture Paint workspace in the Texture Slots panel of the Active Tool and Workspace Settings window of the Properties Editor and create a new texture by clicking the Add a Texture Paint Slot (+) button and choosing Base Color. Retain the default settings by changing only the color to gray and then click OK.

    
4. 4.

   Click Shading in the Topbar to set the workspace with this name. Notice that Blender automatically added a Material Base Color node with the gray texture to the shader Principled BSDF of the object material.

    
5. 5.

   Duplicate the Material Base Color node (Shift+D), create a new image with the node’s New image button to the right of the Texture Name, and call it Lights while keeping the color black.

    
6. 6.

   Add a MixRGB node and change its blending mode from Mix to Add and insert it between the Material Base Color node and the Principled BSDF Node.

    
7. 7.

   Connect the Color output of the Lights node with input Color2 of the RGB Mix Node.

    
8. 8.

   Duplicate the Lights node and add a new texture as previously, by pressing the node’s New image button to the right of the Texture name, but make it white by changing the Color in the Color box and call it Shadows.

    
9. 9.

   Add another RGB Mix node, and this time use the Multiply blending mode. Insert it between the previous RGB Mix node and the Principled BSDF shader, and then connect the Color output of the Shadows node with input Color 2 of the RGB Mix node.

    
10. 10.

    Change the object mode of 3D view from Object to Texture Paint.

     
11. 11.

    Open the Active Tool and Workspace Settings window in the Properties Editor.

    In the Texture Slots panel, click the Material Base Color.

    Change the color from white to gray in the brush Color Picker, and paint the 3D Viewport object.

     
12. 12.

    Then select the Lights slot, try to paint over this slot, and repeat the same operation with Shadows, as shown in Figure 5-44.

     

With this technique, we can easily paint on three levels, creating black-and-white spots on our teapot, as shown in the figure.

As we can notice, painting with the gray brush on the Material Base Color layer doesn’t result.

Instead, if we paint on the Lights layer, we get a lighter color, and painting on the Shadows layer gets darker. So, we have built two layers to control lights and the intensity of the shadows.

Also, by changing the factor of the two nodes, Add and Multiply, we can modify the shades of the two slots, Lights and Shadows. Modifying the Factor value of Add, we change the intensity of the lights. Likewise, while adjusting the Factor value of Multiply, we influence the power of the shadows. We have the maximum contrast with a value of 1, while with the value 0, the tones are uniform.

Let’s expand this example using another channel we can create in the texture slots: a Normal map.

Drawing a Bump Map Directly on the Object

We learned how to create textures in the texture slot for the Base Color, i.e., the Diffuse maps.

Now let’s add a Bump map to the teapot by following these steps:

1. 1.

   Go to the Texture Paint workspace and create a new texture from the Texture Slots panel of the Active Tool and Workspace Settings window of the Properties Editor by clicking the Add a Texture Paint Slot (+) button and choosing Bump. Keep the default settings by changing only the color to gray and clicking OK.

   In the Shader editor Blender automatically adds a Bump node connected to the normal input of the Principled BSDF shader. In addition, to simulate the relief, Blender adds an Image node with the texture Material Bump.

    
2. 2.

   In the Texture Paint editor paint on the teapot with the black-and-white brush while keeping the Material Bump slot selected.

   Now, if you draw with white, you get a relief effect, and if you paint with black, you get a hollow result. You can see the result in Material Preview or Rendered Viewport Shading display. But, of course, we don’t change the geometry this way.

   Instead, we get a Bump texture that simulates the relief, with the node chain shown in Figure 5-45.

    

We can also add maps for other channels by creating them in the texture slots, editing them in Blender, and eventually exporting them to other software.

So far, we have created textures in different ways inside Blender. We also looked at modifying them directly in the software or externally in Krita or similar programs. This software has many brushes and an almost endless possibility of creating textures.

That concludes this chapter on painting inside and outside Blender.

As we have seen, we can use the painting tools very flexibly, either to paint directly into Blender or to create images or textures for our materials.