Grease Pencil - Draw Mode - Brush Size Indicator Incorrect #82707

New Issue

Jamell Moore · 2020-11-13T20:36:22+01:00

Jamell Moore commented

2020-11-13 20:36:22 +01:00

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTS 450/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 391.35

Blender Version
Broken: version: 2.92.0 Alpha, branch: master, commit date: 2020-11-12 09:12, hash: fb4113defb
Worked: none (testing in r2.91 also but doesn't work as expected)

Description of Issue

In Grease Pencil Draw mode, when adjusting the brush size using the F key the size indicator doesn't match the size of the applied stroke. This is the case when stroke_thickness_space is set to either "World Space" or "Screen Space".

User Story / Expected Result

I thought I would try out the the Grease Pencil for the first time but I couldn't move
past setting the brush size effectively. At first I was confused by the fact that the brush size was called 'radius' rather than 'thickness'... BUT I thought I would try to move past this by changing the size visually using the brush size tool (Hotkey F).

I immediately found that the tool was impossible to work with because the indicator is sized in screen space with no relation to the world space.

Therefore I decided to try using the draw tool with stroke_thickness_space set to "Screen Space". I was expecting that the indicator for the draw tool would match the size of the drawn stroke but I saw that the indicator appeared double the size.

I took a screenshot and measured the size of the applied stroke the indicator for the brush tool and the indicator is indeed double the size.

I'm guessing the fact that the brush size is called 'radius' rather than called thickness' has caused confusion somewhere. I'm not familiar with the code yet so I can't check where the problem lie.

Steps to reproduce - screen_space issue

Create a new file using File->New->2d Animation
Set the view to Orthographic
Change to draw mode
Select the draw tool
Change Stroke Thickness Space to Screen Space. Object Data Properties->Stroke Thickness->Screen Space
Draw a single point in the center of the world
Now press the F key from the origin of the point
You will see that the brush size doesn't match the size of the stroke.

Steps to reproduce - world_space issue

Create a new file using File->New->2d Animation
Set the view to Orthographic
Change to draw mode
Select the draw tool
Change Stroke Thickness Space to world space. Object Data Properties->Stroke Thickness->Screen Space
Draw a single point in the center of the world
Now press the F key from the origin of the point
You will see that the brush size doesn't match the size of the stroke.
Additional steps
1. Print the screen after pressing the F key
2. Measure the size of the brush size visual indicator in pixels using any graphics application. Note down the measurement.
3. Zoom in or out in the viewport
4. Activate the brush size tool again using 'F' key
5. Take another screenshot and measure the brush size indicator again.
6. The measurement will match the size of the previous measurement. Indicating that the tool is set to the absolute size of the brush setting in screen_space rather than taking into account the stroke size in 3D World Space.

Suggestions

Change the name of the brush size setting from 'radius' to 'thickness' or width (more inline with SVG) and ensure the indicator is set to the same size with both world space and screen space settings for stroke_thickness_space.
Update the documentation to state how the stroke size in pixel relates to world space dimensions. From my measurements a pixel is 1/1000th of a meter (1mm). If you draw a stroke/point 1000px in the viewport it measures 1m in diameter. Note that this is assuming that stroke size is the diameter not the radius! Another reason why I think there has been some confusion caused by the terminology. I doubt 1px would have been defined as 1/500th of a meter.

**System Information** Operating system: Windows-10-10.0.18362-SP0 64 Bits Graphics card: GeForce GTS 450/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 391.35 **Blender Version** Broken: version: 2.92.0 Alpha, branch: master, commit date: 2020-11-12 09:12, hash: `fb4113defb` Worked: none (testing in r2.91 also but doesn't work as expected) **Description of Issue** In Grease Pencil Draw mode, when adjusting the brush size using the `F` key the size indicator doesn't match the size of the applied stroke. This is the case when stroke_thickness_space is set to either "World Space" or "Screen Space". **User Story / Expected Result** I thought I would try out the the Grease Pencil for the first time but I couldn't move past setting the brush size effectively. At first I was confused by the fact that the brush size was called 'radius' rather than 'thickness'... BUT I thought I would try to move past this by changing the size visually using the brush size tool (Hotkey `F`). I immediately found that the tool was impossible to work with because the indicator is sized in screen space with no relation to the world space. Therefore I decided to try using the draw tool with stroke_thickness_space set to "Screen Space". I was expecting that the indicator for the draw tool would match the size of the drawn stroke but I saw that the indicator appeared double the size. I took a screenshot and measured the size of the applied stroke the indicator for the brush tool and the indicator is indeed double the size. I'm guessing the fact that the brush size is called 'radius' rather than called thickness' has caused confusion somewhere. I'm not familiar with the code yet so I can't check where the problem lie. **Steps to reproduce - screen_space issue** 1. Create a new file using File->New->2d Animation 2. Set the view to Orthographic 3. Change to draw mode 4. Select the draw tool 5. Change Stroke Thickness Space to Screen Space. Object Data Properties->Stroke Thickness->Screen Space 6. Draw a single point in the center of the world 7. Now press the F key from the origin of the point 8. You will see that the brush size doesn't match the size of the stroke. **Steps to reproduce - world_space issue** 1. Create a new file using File->New->2d Animation 2. Set the view to Orthographic 3. Change to draw mode 4. Select the draw tool 5. Change Stroke Thickness Space to world space. Object Data Properties->Stroke Thickness->Screen Space 6. Draw a single point in the center of the world 7. Now press the F key from the origin of the point 8. You will see that the brush size doesn't match the size of the stroke. 9. Additional steps 1. Print the screen after pressing the F key 2. Measure the size of the brush size visual indicator in pixels using any graphics application. Note down the measurement. 3. Zoom in or out in the viewport 4. Activate the brush size tool again using 'F' key 5. Take another screenshot and measure the brush size indicator again. 6. The measurement will match the size of the previous measurement. Indicating that the tool is set to the absolute size of the brush setting in screen_space rather than taking into account the stroke size in 3D World Space. **Suggestions** 1. Change the name of the brush size setting from 'radius' to 'thickness' or width (more inline with SVG) and ensure the indicator is set to the same size with both world space and screen space settings for stroke_thickness_space. 2. Update the documentation to state how the stroke size in pixel relates to world space dimensions. From my measurements a pixel is 1/1000th of a meter (1mm). If you draw a stroke/point 1000px in the viewport it measures 1m in diameter. Note that this is assuming that stroke size is the diameter not the radius! Another reason why I think there has been some confusion caused by the terminology. I doubt 1px would have been defined as 1/500th of a meter.

Jamell Moore commented

2020-11-13 20:36:22 +01:00

Added subscriber: @JamellMoore

Antonio Vazquez commented

2020-11-13 21:42:49 +01:00

Added subscriber: @antoniov

Antonio Vazquez commented

2020-11-13 21:42:49 +01:00

The radius name is used because we follow Blender names, and all brushes are always radius, not thickness.

About real thickness, in a 3D environment is not easy to define what will be the final thickness of the stroke on the screen. When you compare with SVG, you are using a wrong comparison, SVG is 2D and the things are totally different. Anyway, we have in the Todo list to work on the relationship between defined size and feedback of the result size.

The `radius` name is used because we follow Blender names, and all brushes are always radius, not thickness. About real thickness, in a 3D environment is not easy to define what will be the final thickness of the stroke on the screen. When you compare with SVG, you are using a wrong comparison, SVG is 2D and the things are totally different. Anyway, we have in the Todo list to work on the relationship between defined size and feedback of the result size.

Richard Antalik commented

2020-11-14 03:53:21 +01:00

Added subscriber: @iss

Richard Antalik commented

2020-11-14 03:53:21 +01:00

Changed status from 'Needs Triage' to: 'Archived'

Richard Antalik closed this issue

2020-11-14 03:53:21 +01:00

Richard Antalik self-assigned this 2020-11-14 03:53:21 +01:00

Richard Antalik commented

2020-11-14 03:53:21 +01:00

Since this is already covered by existing TODO, I will close this report. Thanks for reporting though.

Jamell Moore commented

2020-11-14 06:15:26 +01:00

Thanks for your reply Antonio. I've had a look at the other modes and can now see understand why it was called radius rather than thickness. I was thrown off when changing to screen_space because the indicator was double the size. I thought radius may have been oddly used as a synonym for thickness/diameter.

I was reluctant to include examples using the tool in world space because I understand that its not easy to define the final thickness in 3d but I thought the indicator would at least match when stroke_thickness_space is set to screen_space and the view in orthographic projection, facing the stroke plane. Isn't the radius and thickness well defined in this context?

You guys understand far more than I do and I respect your knowledge in this area. If you could spare some time to explain why the indicator can't match in this context I would really appreciate it. I feel like I'm missing something.

Thanks for your reply Antonio. I've had a look at the other modes and can now see understand why it was called radius rather than thickness. I was thrown off when changing to screen_space because the indicator was double the size. I thought radius may have been oddly used as a synonym for thickness/diameter. I was reluctant to include examples using the tool in world space because I understand that its not easy to define the final thickness in 3d but I thought the indicator would at least match when stroke_thickness_space is set to screen_space and the view in orthographic projection, facing the stroke plane. Isn't the radius and thickness well defined in this context? You guys understand far more than I do and I respect your knowledge in this area. If you could spare some time to explain why the indicator can't match in this context I would really appreciate it. I feel like I'm missing something.

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Grease Pencil - Draw Mode - Brush Size Indicator Incorrect #82707