Angle option of new GP brush settings is too restricted in value #49102

New Issue

Bastien Montagne · 2016-08-16T22:46:36+02:00

Bastien Montagne commented

2016-08-16 22:46:36 +02:00

Currently, this value is limited to range [0°, 90°], which excludes half of possible values.

Either this setting shall be in [0°, 180°] range, or it should apply a 'mirror' effect (but really do not see why it’s limited to 90° max…).

Currently, this value is limited to range [0°, 90°], which excludes half of possible values. Either this setting shall be in [0°, 180°] range, or it should apply a 'mirror' effect (but really do not see why it’s limited to 90° max…).

Antonio Vazquez was assigned by Bastien Montagne

2016-08-16 22:46:36 +02:00

Bastien Montagne commented

2016-08-16 22:46:36 +02:00

Changed status to: 'Open'

Bastien Montagne commented

2016-08-16 22:46:36 +02:00

Added subscriber: @mont29

Antonio Vazquez commented

2016-08-17 09:05:11 +02:00

@mont29 This is done by design and there is a reason to do it.

The angle is the position of the brush and only can be between 0 and 90 degrees because if you change the orientation more than 90 degrees, really you are near of 0 again.

You can find the explanation here: https://wiki.blender.org/index.php/User:Antoniov/Grease_Pencil_Design_Changes#Drawing_Brushes

@mont29 This is done by design and there is a reason to do it. The angle is the position of the brush and only can be between 0 and 90 degrees because if you change the orientation more than 90 degrees, really you are near of 0 again. You can find the explanation here: https://wiki.blender.org/index.php/User:Antoniov/Grease_Pencil_Design_Changes#Drawing_Brushes

Bastien Montagne commented

2016-08-17 10:14:48 +02:00

@antoniov No it’s not the only possible/needed values. Above 90 (or below 0) you indeed get “closer” to zero again, but “from the other way around” if I may say so (cos(45) == -cos(135), the [90, 180] range is some kind of mirror of the [0, 90] range). This picture should make it obvious:

There is currently no way to get falling slope thick and rising one thin - you’d need either -45 or 135 as Angle value for that.

@antoniov No it’s not the only possible/needed values. Above 90 (or below 0) you indeed get “closer” to zero again, but “from the other way around” if I may say so (`cos(45) == -cos(135)`, the [90, 180] range is some kind of mirror of the [0, 90] range). This picture should make it obvious: ![Capture d’écran_2016-08-17_10-04-35.png](https://archive.blender.org/developer/F338101/Capture_d_écran_2016-08-17_10-04-35.png) There is currently no way to get falling slope thick and rising one thin - you’d need either -45 or 135 as `Angle` value for that.

Antonio Vazquez commented

2016-08-17 11:43:33 +02:00

@mont29 I see the problem now, but I think I need to fix this in the code, not in the UI. Set an angle greater of 90 is not artist friendly. Really, if you turn a marker, you get different thickness in the first 90 degrees, later, you get again the same size but oposed.

Bastien Montagne commented

2016-08-17 11:53:37 +02:00

I do not agree at all here - with a real life marker, you have different results for a full 180° range. The fact that, for the same direction of stroke, you get symmetric results when turning beyond the [0, 90] range is not enough, try to change the direction of your stroke and you won’t get the same symmetric results anymore!

You seem to be thinking in 'local space' (stroke direction one), and not in 'global space' (paper sheet). In above picture, you need to turn you marker from +45 to -45 to switch effect (or from +45 to +135, that’s same thing).

Just try it with a real-life marker and a paper sheet if you don’t believe me. ;)

I do not agree at all here - with a real life marker, you have different results for a full 180° range. The fact that, **for the same direction of stroke**, you get symmetric results when turning beyond the [0, 90] range is not enough, try to change the direction of your stroke and you won’t get the same symmetric results anymore! You seem to be thinking in 'local space' (stroke direction one), and not in 'global space' (paper sheet). In above picture, you need to turn you marker from +45 to -45 to switch effect (or from +45 to +135, that’s same thing). Just try it with a real-life marker and a paper sheet if you don’t believe me. ;)

Antonio Vazquez commented

2016-08-17 13:03:47 +02:00

Maybe we are talking of different things.

Here you have an example of how was defined the algorithm for the marker. The example assumes the brush marker angle was defined as 45 degrees. All the time, the function is working with the local space and checking the difference between a full thickness angle and the drawing direction of the last two points. The function assumes the marker is not rotate, only the drawing direction.

As you can see in the graph, when you start to draw in an angle > of 135 degrees, the thickness of the marker increase from the minimum size. With this approach, we get the sense of different thickness when draw a curve.

Think how an artist hold a marker, he is not rotating the pen while drawing. He moves his hand only.

The possible bug (not totally sure, I need to ask artists Daniel M. Lara and Matias Mendiola) is if you draw a line to -45, the marker must be full thickness or not.

Maybe we are talking of different things. Here you have an example of how was defined the algorithm for the marker. The example assumes the brush marker angle was defined as 45 degrees. All the time, the function is working with the local space and checking the difference between a full thickness angle and the drawing direction of the last two points. The function assumes the marker is not rotate, only the drawing direction. ![GP_Marker_Angle.png](https://archive.blender.org/developer/F338138/GP_Marker_Angle.png) As you can see in the graph, when you start to draw in an angle > of 135 degrees, the thickness of the marker increase from the minimum size. With this approach, we get the sense of different thickness when draw a curve. Think how an artist hold a marker, he is not rotating the pen while drawing. He moves his hand only. The possible bug (not totally sure, I need to ask artists Daniel M. Lara and Matias Mendiola) is if you draw a line to -45, the marker must be full thickness or not.

Antonio Vazquez commented

2016-08-17 13:05:20 +02:00

Added subscribers: @pepe-school-land, @mendio

Bastien Montagne commented

2016-08-17 14:46:22 +02:00

I think your pictures shows it as well as mine: you need [-90, +90] (or [0, 180], same thing) range to represent all possible orientations of your marker… Really do not see what’s complicated here… :/

Antonio Vazquez commented

2016-08-17 16:19:16 +02:00

Ok, I 'm going to put -90 to 90 in the range.

I have run some test, and really there isn't great difference drawing, maybe only for left handed people, but anyway is an user option, so doing the range wider, we cover more options.

Ok, I 'm going to put -90 to 90 in the range. I have run some test, and really there isn't great difference drawing, maybe only for left handed people, but anyway is an user option, so doing the range wider, we cover more options.

blender-admin commented

2016-08-17 16:23:05 +02:00

This issue was referenced by ab775b6ae9

This issue was referenced by ab775b6ae9930e1fc6b8536f5ca150557286a119

Antonio Vazquez commented

2016-08-17 16:25:01 +02:00

Changed status from 'Open' to: 'Resolved'

Antonio Vazquez closed this issue

2016-08-17 16:25:01 +02:00

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Angle option of new GP brush settings is too restricted in value #49102