Understanding the ArtRage 4 Blending Engine

[DarkOwnt]

NOTE: With the advent of the custom brush in AR5, blending with paint, and with depth (AR6) has improved markedly.
Many statements in this thread are outdated.

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Hello All:

In order to work with effectively with any tool one needs to understand how it actually works (rather than waste time wishing it behaved in other ways). In this spirit I hope you find this little tutorial of ArtRage's blending engine, useful. Feel free to save the image and use your eye dropper to investigate the results.

The inline image has blended oils, which have been blended using the oil brush only (reset tool with 100% loading). In order to fully understand the blending "trend", each "pair" of colors was blended completely, i.e. until a particular color emerged as the convergence of the other two.

Blending was done with the standard blending mode on (not using the Real Color Blending mode)



Blending tests in area "1" were used to investigate ArtRage Blending Engine's treatment of colors having exactly the same hue, and exactly the same saturation, each pair only differed by luminosity. Pairs of colors were arranged one above each other and blended. All starting colors have a saturation of 50% and a hue of 67% (blue). In the top row of pairs, the bottom color has 20% luminosity, while the luminosity of the top color increases to the right: 33%, 50%, 66%, and 80%, in the second row of pairs, the bottom color has 33% luminosity while the luminosity of the top colors increases to the right: 50%, 66%, and 80%, in the third row the bottom color has 50% while the top colors are 66% and 80% and in the final row the bottom color is 66% luminosity and the top color is 80%. An extra test pair is added to the top right, it has 10% luminosity for the bottom color and 90% luminosity for the top color.

Results for Area 1: in general the color resulting from complete blending has the same hue, an average (more or less) luminosity, but a saturation which is larger than either of the original colors. The larger the difference in luminosity between the colors blended, the larger the divergent increase in saturation. Saturation increases go from 10% to 30% for differences in luminosity from about 13% to 60%. A final test pair was added (top right) which had a difference of 80% in luminosity, the resulting increase in saturation was 40% (from 50% for the original colors to 90% for the resulting color).

Bottom line, blending for the same color having different luminosity values causes increases in saturation


Blending tests in area "2" were used to investigate ArtRage Blending Engine's treatment of colors having exactly the same hue, and exactly the same luminosity, each pair only differed by saturation. All the starting colors have a luminosity of 50% and a hue of 67% (blue). In the top row of pairs, the bottom color has 20% saturation, while the saturation of top color increases to the right: 33%, 50%, 66%, and 80%, in the second row of pairs, the bottom color has 33% saturation while the saturation of the top colors increases to the right: 50%, 66%, and 80%, in the third row the bottom color has 50% while the top colors are 66% and 80% and in the final row the bottom color is 66% saturation and the top color is 80%.

Results for Area 2: in general colors resulting from complete blending have the same hue and luminosity. For pairs of color each having saturation of 50% or below, the resulting colors have average saturation (more or less) of the two colors. This convergence was not temporary, it was permanent and stable. For pairs of colors where one color has a saturation of 66% or 80%, the convergent color is not an average but a color having the 66% or 80% saturation. In other words the convergent color ended up being the one with high saturation, i.e. the high saturation "consumed" the low saturation color. This happens even when the two colors are close in saturation.

Preliminarily it seems that high saturation can overrun a low saturated color of the same hue and same luminosity.

Blending Tests in Area "2B" were conducted to further investigate the "saturation domination" effect. At the top a color having 66% saturation was blended with one with 0% saturation (grey). After complete blending the grey was destroyed, completely replaced by the 66% saturation color. To see where the boundary (at least for 50% luminance) is between blending resulting in an average saturation and blending which results in "saturation dominance" the upper color was varied from 61%, 59%, 58%, 57% saturation and blended with 0% saturation (grey). Interestingly at 61% and 58% there is a side-effect in which the completely blended color has a luminosity lower than either of the original colors. 59% exhibits the standard "saturation dominance" while at 57%, we finally begin to see emergence of a stable convergent completely blended color which is an average of the saturation of the two original colors, and with the same luminance (no luminance reduction).

Bottom line: High saturation can overrun lower saturation colors of the same luminosity and the same hue. Combining some colors of the same hue and luminosity (at about 57% saturation) can result in a completely blended color which is darker than the starting colors. Under 57% when blended with 0% we see the expected result of a color with the same luminosity as the original colors and with an average saturation.


In area 3 colors were chosen as for area 1, in terms of luminosity (varied) and saturation (all 50%), only the upper color have a hue of 67% (blue) and the lower color has a hue of 0% (red). As can be seen when colors vary greatly in luminosity, the resulting completely blended color has a higher saturation than either of the starting colors. It also should be noted that for the first pair of the first row, the resulting color has a lower saturation and a lower luminance than either of the starting colors.


This is only scratching the surface but I hope this helps you all understand how blending works in ArtRage. Keeping in mind how the tool actually works can only help you to use it more effectively.

Sincerely
DO

[DarkOwnt]

In the second post of this series we look at the truly fascinating subject of the ArtRage 4 Blending Engine from the perspective of layer blend modes.

Today we are looking at the way ArtRage 4 does Saturation blending for its Layer Blend mode - "Saturation", and in a future post we will look at Luminosity blending for its Layer Blend mode - "Luminosity"

The following was generated using the gradient function in ArtRage 4, and serves as the background for our layer blending tests. Color ranges from white at the bottom (Sat = 0%, Lum = 100%), blue in the middle (with 50% saturation and 50% luminance), to black at the top (Sat = 0%, Lum = 0%).



In order to determine how the Saturation Layer Blend Mode works a set of red vertical swaths was put in the layer on top of the background. The red swaths are all exactly of the same hue and luminance (Hue = 0%, Lum = 50%) and vary only in Saturation from left to right (0%, 20%, 40%, 50%, 60%, 80%, 100%) Below is shown how the layer looks on top of the background in normal blending mode with opacity set to 100%:



The image that follows results from setting the Layer Blend Mode of the red vertical swaths to "Saturation" (still at 100% Opacity):



Note that each blended swath, has the same hue 67% (blue) which is expected but no longer has the same luminance. The story for the resulting saturation is even more complicated. To really understand what is happening let us look at each swath individually:

First swath starting from the left (left edge): this swath has a saturation of 0% and a hue of 67% (blue) which is to be expected. Interestingly the luminance does vary from 0% at the top to 100% at the bottom, however it has undergone a shift/transformation. The variation is no longer linear (sorry for the math terminology but it accurately describes what is happening) with vertical position (as in the background). You will note that at mid height where the background has a luminance of 50%, this swath has a luminance of 75%. In fact, at every position, the luminance has been increased by some amount. What governs this luminosity shift is somewhat elusive.

Second swath from the left: This swath has a luminance which varies from 83% at the bottom (the background layer has a luminance of 100%) to 63% at mid-height (where background layer has Lum = 50%) to 0% at the top (the same as that of the background). Saturation of this swath varies from 100% at the bottom, to 33% at mid-height, interestingly at 1/3 down from the top it hits 20% (which is the Saturation value of the upper layer) and remains there until near the top where it descends to 0%.

Third swath from the left: This swath has a luminance which varies from 71% at the bottom to 54% at mid-height to 0% at the top. Saturation of this swath varies from 100% at the bottom, to 46% at mid-height, interestingly just below mid-height it hits 40% (which is the Saturation value of the upper layer) and remains there until near the top where it descends to 0%.

Fourth swath from the left: This swath has a luminance which varies from 67% at the bottom to 50% at mid-height to 0% at the top. Saturation of this swath varies from 100% at the bottom, to 50% at mid-height, interestingly it stays at 50% (which is the Saturation value of the upper layer) and remains there until near the top where it descends to 0%.

Fifth swath from the left: This swath has a luminance which varies from 62% at the bottom to 47% at mid-height to 0% at the top. Saturation of this swath varies from 100% at the bottom, to 60% at a position just below mid-height, interestingly it stays at 60% (which is the Saturation value of the upper layer) and remains there until near the top where it descends to 0%.

Sixth swath from the left: This swath has a luminance which varies from 55% at the bottom to 42% at mid-height to 0% at the top. Saturation of this swath varies from 100% at the bottom, to 80% at about 1/5th height from the bottom, interestingly it stays at 80% (which is the Saturation value of the upper layer) and remains there until near the top where it descends to 0%.

Seventh swath from the left: This swath has a luminance which varies from 50% at the bottom to 37% at mid-height to 0% at the top. Saturation of this swath is constant at 100%.


Bottom Line: Saturation Blending mode causes shifts in luminance. There is likely a pattern but it is elusive presently. It seems to depend upon both the saturation and luminance of the background as well as the saturation of the upper layer. I will update the thread if a pattern can be discerned. Saturation Blending mode does not overwrite the saturation of the lower layers with that of the upper layer, it creates a new saturation which varies in an elusive manner, but large areas do end up with the same saturation as the upper layer. What variables lead to this stability, and the exact variation where stability is lacking have yet to be determined.

[DarkOwnt]

In the third post of this series we continue to look at the truly fascinating subject of the ArtRage 4 Blending Engine from the perspective of layer blend modes.

Today we are looking at the way ArtRage 4 does Luminosity blending for its Layer Blend mode - "Luminosity"

As with our saturation test the following was generated using the gradient function in ArtRage 4, and serves as the background for our layer blending tests. Color ranges from white at the bottom (Sat = 0%, Lum = 100%), blue in the middle (with 50% saturation and 50% luminance), to black at the top (Sat = 0%, Lum = 0%).




In order to determine how the Luminosity Layer Blend Mode works a set of red vertical swaths was put in the layer on top of the background. The red swaths are all exactly of the same hue and saturation (Hue = 0%, Sat = 50%) and vary only in luminosity from left to right (0%, 20%, 40%, 50%, 60%, 80%, 100%) Below is shown how the layer looks on top of the background in normal blending mode with opacity set to 100%:



The image that follows results from setting the Layer Blend Mode of the red vertical swaths to "Luminosity" (still at 100% Opacity):



Note that each blended swath, has a hue which varies but is near the original hue of 67% (blue) and has a varying luminance and saturation. To really understand what is happening let us look at each swath individually:

First swath starting from the left (left edge): this swath has a hue of 67% (blue) which is to be expected. Interestingly the saturation is 100% for the entire swath which is unexpected. Luminance varies continuously from 0% at the top to 19% at the middle, back to 0% at the bottom. What governs this luminance shift is somewhat elusive. Essentially none of the resulting swatch except for the extreme ends, has the same luminance as the upper layer (0%) in luminosity blending mode.

Second swath from the left: This swath has a saturation which varies from 0% at the top to 100% at a little above the middle stays at that value until about 1/3 from the bottom after which it again varies back to 0%. Hue varies from 67% at the top to 62% at 1/3 from the bottom back to 67% at the bottom. Luminance varies from 16% at the top to 28% in the middle back to 16% at the bottom. Essentially only two places somewhere between the middle and the ends has the same luminance as the upper layer (20%) in luminosity blending mode.

Third swath from the left: This swath has a saturation which varies from 0% at the top to 50% at the middle and varies back to 0% at the bottom. Hue varies from 67% at the top to 69% at 1/4 from the top to 66% around the middle and back to 67% at the bottom. Luminance varies from 33% at the top to 50% in the middle back to 33% at the bottom. Essentially only two places somewhere between the middle and the ends has the same luminance as the upper layer (40%) in luminosity blending mode.

Fourth swath from the left: This swath has a saturation which varies from 0% at the top to 67% at the middle and varies back to 0% at the bottom. Hue varies from 67% at the top to 69% at 1/4 from the top to 66% around 1/3 up from the bottom and back to 67% at the bottom. Luminance varies from 42% at the top to 61% in the middle back to 42% at the bottom. Essentially only two places somewhere between the middle and the ends has the same luminance as the upper layer (50%) in luminosity blending mode.

Fifth swath from the left: This swath has a saturation which varies from 0% at the top to 96% at the middle and varies back to 0% at the bottom. Hue varies from 67% at the top to 69% at 1/4 from the top to 66% around 1/3 up from the bottom and back to 67% at the bottom. Luminance varies from 53% at the top to 72% in the middle back to 53% at the bottom. Essentially only two places somewhere between the middle and the ends has the same luminance as the upper layer (60%) in luminosity blending mode.

Sixth swath from the left: This swath has a saturation which varies from 0% at the top to 100% at about 1/4 of the way down, stays at 100% until 1/3 from the bottom at which point it starts to vary back down to 0% at the bottom. Hue varies from 67% at the top to 72% at just above the middle back to 67% at the bottom. Luminance varies from 75% at the top to 86% at about 1/3 from the bottom back to 75% at the bottom. Essentially only two places somewhere between 1/3 of the way up and the ends has the same luminance as the upper layer (80%) in luminosity blending mode.

Seventh swath from the left: This swath has a saturation which is at 0% close to the top and bottom and 100% everywhere else. Hue varies from 67% at the top to 83% at about the middle back to 67% at the bottom. Luminance varies from 100% at the top to 96% at the middle back to 100% at the bottom. Essentially only two places, the top and the bottom, have the same luminance as the upper layer (100%) in luminosity blending mode.


Bottom Line: Luminosity Blending mode causes shifts in saturation and hue. There is likely a pattern but it is elusive presently. It seems to depend upon the saturation and luminance and hue of the background as well as the luminosity and possibly hue of the upper layer. I will update the thread if a pattern can be discerned. Luminosity Blending mode does not overwrite the luminosity of the lower layers with that of the upper layer, it creates a new luminosity which varies, in an elusive manner, but at least two points on each swath do end up with the same luminosity as the upper layer. What variables lead to these areas have yet to be determined.



BLENDING MODE CONCLUSIONS


It may seem a little confusing to determine how these modes work. Saturation blending mode causes shifts in luminance and luminosity blending mode causes shifts in saturation and hue. The resulting saturation in saturation blending mode and the resulting luminance in luminosity blending mode is a complex variation which does not reflect simply the saturation and respectively the luminance of the upper layer. The result is a complex combination of luminosity and saturation of likely both layers. Keep in mind what you have learned about how these swaths affect saturation, luminosity, and hue of the lower color with values of the upper color in these blending modes and hopefully you can produce better artwork with more predictable results when using Saturation and Luminosity blending modes.




Next Time: Airbrush and InkPen Blending modes

[aardbewoner]

Thanks to unravel the mysteries of Artrage

[williamK]

Thank you. This provides an insight that I didn't have before. Not a simple subject.

[DarkOwnt]

Spoke too soon about InkPen and Airbrush blending modes. Saturation and Luminosity blend modes would have been of interest but they work substantially the same as the layer blending modes described above.

Next: Some techniques for smooth blending and saturation/luminosity artifact correction.

[DarkOwnt]

This basic blocked in ball on a plane with a yet to be gradient background will form the starting point for some blending "methods" which take into account the behavior noted above.



With this method, the goal is to blend the existing colors, to get all of the colors in the final image. There will be some needed corrections made along the way.

[DarkOwnt]

This is an example of what can result from blending the above image using only a blending palette knife. Note, the ball is on a separate layer from the plane, which is also on a separate layer from the background. Notice in some areas the saturation artifacts are becoming visible. In particular on the ball and on the plane.



To treat these artifacts the following (derived from the investigations above) is an effective technique to compensate for erroneous colors.

1. Duplicate the layer to be corrected (e.g. the ball)
2. Ensure the top duplicated layer is set to a normal blending mode.
3. In the top duplicated layer, use the airbrush, at a low opacity (for example 15%) and with a low hardness (for example 0%) and at the proper size to address features you wish to correct.
I) Here is the important part, set the blend mode of the air brush to saturation mode.
II) Pick a color (press alt) within an area you find to have too high a saturation keeping note of the luminosity.
III) Adjust the saturation of the picked color by reducing it to a level below what your goal saturation will be (for example 15% below the desired saturation).
IV) Begin correcting with the airbrush until you notice the color is slightly greyer (less saturated) than desired. It is important, because of the interplay between saturation and luminance that you stay in areas of the same luminosity (and possibly hue) when you are correcting. Once you have corrected the saturation of areas of the same luminosity (and possibly hue), pick another color which needs correcting (at a different luminosity), reduce the saturation of that color, and correct until those areas are slightly grey. The reason why I suggest overcorrecting is because it is easier to control and see.
V) Once you have over corrected everything to the degree you deem is sufficient, tweak the top duplicate layer's opacity (lower it) until the areas you have overcorrected have the desired saturation, i.e. just the right amount of correction. Please note some irregularity in saturation is not a bad thing if it is subtle, and if it looks the way you intend it to.
VI) If need be, go in and readjust the top duplicate layer more using this technique.


The following shows the results obtained using this technique on the ball and on the plane separately. Notice the saturation errors and artifacts in the areas of blending is much less pronounced, but the overall palette knife blended feel of those areas remains intact. This is where you get the benefit of this technique, brush strokes and blending strokes still remain. [If you wanted the painting to look like it was airbrushed from the start, you could simply paint the whole thing using an airbrush, and blending artifacts would never have been an issue.]



If after having looked at the erroneously saturated ball for too long you now want to increase the saturation of the overall image you can do so with the adjust layer colors in the Edit menu. The result although more saturated than your original concept will be more evenly/correctly saturated due to your work correcting it.

Next time we'll look at some things that can be done about the blending of the background, and then some gratuitous tweaks will also be discussed.

[DarkOwnt]

This basic blocked in ball on a plane with a yet to be gradient background will form the starting point for some blending "methods" which take into account the behavior noted above.



With this method, the goal is to blend the existing colors, to get all of the colors in the final image. There will be some needed corrections made along the way.

Hello all. I'll soon be updating this with a method that uses an approach similar to glazing with an oil brush... i.e. with thinners turned way up, insta dry ON, and autoclean ON. It can be used to create smooth blended gradients with no saturation artifacts.

[markw]

Great news, looking forward to it