GPencil: Screen-space stroke size incorrect #83675

New Issue

Jamell Moore · 2020-12-11T19:35:06+01:00

Jamell Moore commented

2020-12-11 19:35:06 +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
Worked: none found

Description

When drawing a stroke with a defined pixel size and stroke-thickness-space is set to screen space, the radius of the drawn stroke should measure the set pixel size. This is not the case. The strokes radius measures half the size.

Steps to reproduce

Create a grease pencil object
Set the stroke-thickness-space to screen space in objects grease pencil settings
Set the brush size to 100px
Draw a single dot.
Print the screen
Measure the dot size in any image editing app.

You will see that the radius of measures 50px and the diameter measures 100px. Instead of 100px and 200px respectively.

This issue can be further seen by trying to change the brush size using the f key. The brush size cursor is drawn at the correct size but is double the size of the stroke.

Investigations

This relates to my original report #82707 wherein I thought the cursor size was incorrect. I have now had time to review the code enough to understand how the cursor is drawn; and how the brush size is defined and passed to the rendering engine.

I have confirmed that the brush size takes the following path.

Brush.size user setting: RADIUS → bGPDstroke.thickness: RADIUS → gpencil_vert.glsl thickness: RADIUS

Simplified for explanation purposes. Path steps missing.

I originally thought thickness was defined as a diameter but this is not the case.

I also thought this would be a noticeable fix but I haven’t found where the issue lie yet so I thought I would report again.

Note: When drawing a stroke with stroke-thickness-space set to world space the stroke is mapped to the users screen correctly. When world space is used a stroke with a brush size of 2000px is drawn with a radius of 1m in world space as defined internally.

Bug-GPencil-Screen-Space-Stroke-Size-Incorrect-Report-VID.mp4

**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 Worked: none found **Description** When drawing a stroke with a defined pixel size and stroke-thickness-space is set to screen space, the radius of the drawn stroke should measure the set pixel size. This is not the case. The strokes radius measures half the size. **Steps to reproduce** - Create a grease pencil object - Set the stroke-thickness-space to screen space in objects grease pencil settings - Set the brush size to 100px - Draw a single dot. - Print the screen - Measure the dot size in any image editing app. # You will see that the radius of measures 50px and the diameter measures 100px. Instead of 100px and 200px respectively. This issue can be further seen by trying to change the brush size using the `f` key. The brush size cursor is drawn at the correct size but is double the size of the stroke. **Investigations** This relates to my original report #82707 wherein I thought the cursor size was incorrect. I have now had time to review the code enough to understand how the cursor is drawn; and how the brush size is defined and passed to the rendering engine. I have confirmed that the brush size takes the following path. Brush.size user setting: RADIUS → bGPDstroke.thickness: RADIUS → gpencil_vert.glsl thickness: RADIUS *Simplified for explanation purposes. Path steps missing.* I originally thought thickness was defined as a diameter but this is not the case. I also thought this would be a noticeable fix but I haven’t found where the issue lie yet so I thought I would report again. Note: When drawing a stroke with stroke-thickness-space set to world space the stroke is mapped to the users screen correctly. When world space is used a stroke with a brush size of 2000px is drawn with a radius of 1m in world space as defined internally. [Bug-GPencil-Screen-Space-Stroke-Size-Incorrect-Report-VID.mp4](https://archive.blender.org/developer/F9503154/Bug-GPencil-Screen-Space-Stroke-Size-Incorrect-Report-VID.mp4)

Jamell Moore commented

2020-12-11 19:35:06 +01:00

Added subscriber: @JamellMoore

Adam Earle commented

2020-12-12 01:44:45 +01:00

Added subscriber: @AdamEarle

Adam Earle commented

2020-12-12 01:44:45 +01:00

I wonder if this was set up for working through the camera? have you checked that?

Germano Cavalcante commented

2020-12-15 15:06:19 +01:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2020-12-15 15:06:19 +01:00

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

Germano Cavalcante commented

2020-12-15 15:06:19 +01:00

At first it seems to be a problem with just the name "Radius" which should be "Diameter". But the fact that the brush size shown when clicking F is twice as large reveals that there is an inconsistency.
So I am confirming it as a Bug.

At first it seems to be a problem with just the name "Radius" which should be "Diameter". But the fact that the brush size shown when clicking F is twice as large reveals that there is an inconsistency. So I am confirming it as a Bug.

Philipp Oeser removed the

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GPencil: Screen-space stroke size incorrect #83675

You will see that the radius of measures 50px and the diameter measures 100px. Instead of 100px and 200px respectively.