Strange Behavior of Strokes with Vector Brushes

[LionelD]

I'm running the latest published AD2 on an M3 MBP under latest published Sequoia.

I believe I have found a bug related to varying the width of a vector brush stroke along its length, so I'm looking for confirmation and any workarounds you might be able to suggest.  Examples in the attached document.

The problem is that reducing the width of a vector brush stroke progressively introduces transparency in the regions made narrower than the value established in the Stroke panel.  This happens with at least some vector brushes included with AD2 (they must permit variable stroke weight) as well as at least one brush that I made.

The attached document contains 4 colored curves, and one white one, all on a larger black background.  The colors weree chosen to maximize visibility (my eyes are not so god at the moment).  The white one is primarily for making Transparency in the overlapping strokes more visible, can be ignored otherwise.

Stroke Width for upper 4 curves was established at 300pt in the Stroke Studio.  Layers are named for the vector brush used.

The Problem: Using either the Pressure Profile in the Stroke studio or the Stroke Weight tool, reducing width near the centre of the colored curves makes them transparent in that region.

1. [ and ] keys operate on the stroke as a whole, and do not appear to alter transparency/opacity
2. The Pressure Profile in Stroke Studio allows stroke weight to vary along the length of the curve; making it narrower makes the stroke progressively more transparent in that region.  Why?
3. The Stroke Weight Tool enables you to make stroke weight narrower and wider than the value set in the Stroke Studio.  Making stroke weight narrower progressively makes the stroke more transparent in that region.  Why?  If you then make it wider, the stroke progressively recovers its opacity, and retains it even if you make the stroke wider than the initial value.
4. This happens with ALL the coloured brushes in this document, not just the one I made.

@NathanC  Any chance this is related to AF-1453?  I saw you mentioned it at

 

Vector Brushes - Changing Width CHanges Opacity too.afdesign

Edited November 4, 2024 by LionelD

[LionelD]

I forgot to state this concerns Textured Intensity Brushes.  Sorry.

Regards

[Ldina]

2 hours ago, LionelD said:

I forgot to state this concerns Textured Intensity Brushes.

Hi Lionel.

I don't think this is the same issue I was reporting. If I understand you correctly, as the stroke width varies from full width at the start, to a narrower width near the end, you are concerned about the brush stroke becoming more transparent, right? 

If that's the case, then I think the brush is performing as designed. In the screenshot below, I double clicked the Flat Watercolor 02 Brush in the Brushes Panel, which opened it in the Brush Editing window. First, the brush stroke nozzle has some transparency built into it by design (shown in areas less than solid white). More importantly, the Opacity Variance of the Brush is set to 100%. As the stroke gets narrower, you end up with more transparency, which is what is dictated by having opacity variance set to 100%. So if your brush stroke width is set to 300 px wide, the start of the stroke which is 300 px wide should have 100% opacity.. As the stroke width gets narrower (using pressure graph, line width tool, or pressure sensitive tablet), the opacity should decrease until it reaches 0% opacity at the narrow end of the stroke, where the stroke width is 0 px wide. You can see that in the preview, which I have marked with an oval. You need the Controller to be set to Pressure or Brush Default for that to happen, which will cause the brush size and opacity variance defined in the brush to take effect. In other words, as the stroke pressure decreases, the stroke will get narrower AND lower opacity.

If you want to have NO opacity variance as the stroke width changes, set the Opacity Variance in the brush to 0% variance (temporarily or permanently, or duplicate the brush and create a second brush without any opacity variance). You should also be able to set the controller in the brush context menu to "None" before creating the stroke, which should ignore the size and opacity variance (i.e., NONE) and give you a 300 px stroke from beginning to end, with no opacity variance. I think I have that right. I apologize if I misunderstood your request.. Hope this helps.

[LionelD]

@Ldina Thanks for taking the time to write such a detailed response.  You explained a lot that I hadn’t understood.  Now I feel rather foolish for asserting this behaviour is a bug.

 Going to re-read your response and see where that gets me.

Thank you very much!

Regards

Lionel

[Ldina]

@LionelD Vector Brushes can be a bit confusing and take some time to learn. I'm still learning and not 100% sure I have it all figured out yet. I will share a graphic that I think sums it up and perhaps makes it a bit easier to understand. You have BOTH brush defaults, and Controller options when using a brush. They interact with one another. Below is my current understanding and experience. It can get complicated with all these controls and abilities to vary brush behavior. I hope this is helpful.

[LionelD]

@Ldina Thanks, you have been very helpful and I appreciate that very much.

I am reworking a test document taking advantage of your input, so I’ll let ou know what transpires.

Regards

Lionel

[Ldina]

@LionelD Glad that was helpful.

Let me know how your test document works out, especially if you find I was in error about anything. 

[LionelD]

@Ldina Hi, I've attached 4 files: an AD2 doc, 3 X PNG Nozzles and a set of exported brushes.

I made 3 nozzles with test strokes.  The first one is the one that's most important to me.  I included a black background for the first 2 nozzles because that seems to be the general guidance, but I don't know how authoritative that is, and a red background in Nozzle 3 just to see if it makes a difference.  Each nozzle includes an additional layer consisting of a solid white stroke intended to expose any transparency.  You can see it in Nozzles 2 and 3, but not Nozzle 1, consistent with how the nozzles are made.

When there's a black background, there are two ways to create something that looks like Nozzle 1 in the AD file:  1) a black-white-black gradient, with opacity at 100% for all 3 nodes, and 2) a White-White-White gradient with opacity 0, 100 and 0 for each node respectively.  The second approach deliberately introduces opacity into the nozzle, so it's no surprise it's apparent in the brush stroke.  However, if you use a black-white-black gradient with each node in the gradient at 100% opacity, the entire gradient is opaque and you do not see the white stroke hidden underneath it - even after exporting to PNG for the nozzle.

If you import Nozzle 1.PNG and Nozzle 2.PNG and place them over any colored layer, you don't see any transparency.  So when the Nozzle 1 brush produces transparent regions I'm surprised.

Each Nozzle measures exactly 420px X 60px, and the whole document is set to 300DPI.  There are color patches under the test strokes that show where the 420px repeat length for each brush should end up.  Each stroke is exactly 4200px long, so there should be 10 whole repeats if you set the stroke width appropriately.  I got them to match at a stroke width of approximately 11pt (about 46px) by experimenting with the width of the test strokes.  I haven't figured out how that relationship works.

Regards

Lionel

Degrees of Opacity 01.afdesign Degrees of Opacity Brushes.afbrushes

[Ldina]

1 hour ago, LionelD said:

I've attached 4 files: an AD2 doc, 3 X PNG Nozzles and a set of exported brushes.

No PNGs were attached, only the afdesign file and the afbrushes file. They all seem to be working as I'd expect.

Vector Intensity Brushes work entirely on opacity. What is white in your exported PNG will be 100% opacity in your final brush. What is black in your exported PNG will be 0% opacity. Shades of gray will have opacity levels between 0-100% depending on the shade of gray. So, a 50% gray in your exported PNG will have 50% opacity in your brush. This is why they suggest using just white, black and shades of gray, to make it easier to visualize the final brush result for Intensity brushes. You can pick any stroke color when using your brush, but the PNG you export controls the opacity (assuming you don't add Opacity Variance in the brush settings).

I've never used a color to create an Intensity brush, but I suspect Affinity will use the "weighted grayscale equivalent" of the color you chose to determine the opacity. So, I'm guessing the red you chose will have an opacity somewhere between white and black, based on the grayscale weighting. I've used color when creating some Vector Image Brushes, and for some Pixel based brushes, but I've always stuck with Black, White and shades of Gray for Vector Intensity Brushes. 

Just remember that for Vector Intensity Brushes, what is white in your PNG will be 100% opacity, what is Black in your PNG will be 0% opacity, and grays will fall in between. The light grays will be high opacity (close to white, which is 100% opacity), and the dark grays will be low opacity (close to black, which is 0% opacity). It's the shades of gray in your exported PNG that control opacity. Visually, white at 100% opacity and black at 0% opacity seems backwards, but it mimics masks (white reveals, black conceals). 

I'm not sure that was very helpful. But your brushes seem to be behaving as expected, based on the afdesign mockup of your brushes. 

[LionelD]

@Ldina Well, very informative as usual, thanks. Now I will have to experiment to find out exactly how much transparency I can tolerate to get the contrast I need in some stuff I'm about to make. The PNG files were embedded in my last post, above, and the afdesign file has the slices to export them.

Changing the subject, I've just noticed your list of equipment - same printer here, i1 Display and Adobe CC for photographers (I would dump them if I could).

Thanks again, you truly explained a lot of stuff I did not know (and can't find at any authoritative web site).

Keep well.

Lionel

 

[Ldina]

 

[Ldina]

1 hour ago, LionelD said:

I will have to experiment to find out exactly how much transparency I can tolerate to get the contrast I need in some stuff I'm about to make.

You can create your strokes without ANY transparency variance (i.e., solid along the length of your stroke), and use the Gradient or Transparency Tools to add transparency as desired, individual stroke by stroke, if desired. You can add many "stops" to the gradient path to control the exact amount of transparency. Just food for thought. I'm not sure what you plan to do, so that may or may not be a starter.

[LionelD]

@Ldina I tend to use gradients a lot, will have to learn more about the transparency tool.  I think the biggest lesson for me is the way that Opacity and Size Variance settings for a brush are coupled to each other.  I had absolutely no idea.  And your graphic about the brush Controller was very illuminating.  I think I haven't absorbed all of this thread yet.

I need to find a way to introduce contrast over and above color, so I will continue looking.  Shades of gray in a nozzle might be enough if I can keep it very subtle, but we make things for other people's eyes and some are not so good.

Thanks for your time and the help you provided.

Regards

Lionel