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September 21st, 2005 #1
Adding Impasto Depth to a Brush in Corel Painter
Adding Impasto Depth to a Brush in Corel Painter
In our previous installments (Creating a Static Bristle Brush, Creating a Smeary Oil Brush) we learned how to create an expressive oil brush with many customizable attributes. These attributes (number of bristles, bristle thickness, color resaturation and bleed via the Well palette, etc.) enable you to perform what I refer to as season-to-taste adjustments. Each user will adjust these attributes according to their personal taste; the result is a unique brush for each user.
In this installment we will add a sense of three-dimensional depth to our brush. This appearance of depth adds a physical quality to brush strokes, causing them appear much like a photograph of traditionally painted oils. The technique of thickly applied oil (or acrylics, for that matter) is known as impasto. The use of impasto provides an additional visual quality to a painting. Impasto celebrates the physical quality of the painting medium. Let's get started!
Painter's Thickening Agent: The Impasto Layer
Painter creates the illusion of depth via its Impasto Layer. This information is actually maintained as a height map similar to the way that bump maps are created in 3D applications. As an impasto-enabled brush is painted with in Painter, a grayscale image is simultaneously created and used to represent a shallow amount of depth in the image. Coupled with a virtual light source, this shallow depth is brought to life as areas of highlight and shadow.
One way to visualize Impasto data is to compare it to the earth's topography. By default, impasto strokes are built up from sea level. Eventually, the built-up impasto data reaches its mountain peaks. At the uppermost limit of impasto's height data, the accumulated artwork will begin to top out and appear as if the strokes are pressed against glass. Conversely, impasto height data can be scooped away to the ocean floor, revealing a flat plane that represents the lower extent of the impasto height data.
The primary control for impasto is located -not surprisingly- in the Brush Control's Impasto palette.
Controlling Depth via the Impasto Palette
The primary enabler of depth in Painter is found in the Impasto palette (Brush Controls). The Draw To pop-up list controls whether or not a brush variant will paint as an Impasto brush. Three Impasto options are offered by the Draw To pop-up: Color, Depth, and Color & Depth. The majority of variants in Painter are set to Color. To add the sense of depth to our Smeary Oil Bristle brush, let's change the Draw To pop-up to the Color & Depth option.
Important Note: Unless impasto is enabled when brush strokes are initially painted, you cannot retroactively enable impasto and have the already painted strokes appear to have depth.
The Depth slider adjusts the degree of depth applied to strokes. I recommend a setting between 100% and 200%. Set the Depth's Expression pop-up to Pressure for greater subtlety. The Smoothing slider adjusts how the impasto height information is rendered. Lower settings preserve more detail; higher settings soften detail. At lower settings, individual brush dabs can appear and may be unwanted. I recommend a Smoothing setting of around 160% or greater. Plow controls how an impasto stroke interacts with already applied impasto painting. I recommend a Plow setting of 50% or above.
You can toggle Impasto visibility on and off using the Toggle Impasto Effect button located at the top right of the image window (above the window scroll bar).
Surface Lighting: Impasto's Best Friend
OK, we've seen how impasto depth is created and controlled via Painter's Impasto palette. What else can we do? We can additionally control the subtlety (or heavy-handedness) of Impasto's apparent lighting via the Surface Lighting dialog (Canvas menu). This dialog controls the appearance of depth to existing impasto-enabled artwork.
The appearance of depth is obviously fake; there is no real depth. The eye can be fooled by the addition of apparent highlights and shadows, creating an illusion a variable height surface. By default, Surface Lighting is set to apply a high degree of shine to impasto art. While it provides a part of the illusion of depth, this default setting is a bit high for my taste. Reducing the Shine factor will lessen the high-lit glare. Another method for adjusting the strength of the highlights is to adjust the Light Control's Concentration (Conc) slider upward. This has the effect of reducing the area of a highlight on impasto artwork.
Note that adjustments made to either the Light Controls Brightness or Exposure sliders can produce the potentially undesirable effect of reducing the background lighting. If this happens, just adjust the slider in the opposite direction.
What Does Wet Look Like?
No, this isn't a metaphysical pondering; I want you to think for a moment what makes wet paint look wet: the surface of fresh oil paint is highly reflective. Some of this reflective quality diminishes when the oil is finally dry, but even dried oils exhibit a surface gloss. This is one reason you may want to keep the Shine slider adjusted to portray a bit of a specular highlight on your impasto artwork. What I am going to reveal to you next is not necessary to create successful impasto imagery. However, it does show yet another aspect of Painter's bag of tricks: adding a reflective surface to your impasto strokes.
You may have noticed already that there is a Reflection slider present in Surface Lighting's Appearance of Depth section. It is this control that adds reflections to impasto-based art, but a bit of additional understanding is required to utilize it effectively. In order to add a reflective environment utilizing the Reflection slider, you must have the correct type of Pattern (Tool palette: Pattern Selector) available. In Painter, the type of pattern utilized to simulate a reflective environment is referred to as an environment map. These special patterns look like the reflection in a mirrored sphere. There is a Pattern Library on the Painter IX CD titled, eMap (This Pattern Library is also available on earlier Painter CDs). This library contains a library of various environmental maps that you'll need to successfully add a simulated wet reflection to your impasto art. With the eMap Pattern Library active, you can select among several environments.
With an eMap pattern active, use the Reflection slider to add a reflection to the surface of your impasto art. Note that there is an upper limit to how strong the reflection slider can be pushed. At some point (around 25-30%), the background color of the image will be affected. This can be offset by adjusting the Brightness and Exposure sliders upward to higher values. As the visibility of the reflection is increased, the painted strokes will take on an increased gel-like appearance.
More Impasto Fun
You can explore the many Impasto variants found in the Brush Selector Bar's Impasto Category. Armed with your acquired knowledge of All Things Impasto, you can utilize these variants as starting points and adjust them to your personal preferences. In particular, the Impasto variants starting with the word Depth (Depth Lofter, Depth Eraser, Depth Equalizer, etc.) are great for editing impasto art's sense of height.
If you've managed to make it this far following along with me and these tutorials, you've earned some creative play time. Next week we'll take the knowledge we've gained and apply it to another powerful Painter brush dab type: The Continuous Stroke. Until then, enjoy your new brush and post some examples of your efforts!
Viva la Painter!
Pixels—It's all in how you arrange them!