Extra ghost edge per ngon in UV editor on Intel HD gfx #60762

New Issue

Celeste Wouters · 2019-01-22T19:59:33+01:00

Celeste Wouters commented

2019-01-22 19:59:33 +01:00

System Information
Arch Linux

Linux 4.20.2-1-ck-ivybridge
Intel i5-3317U w/ Intel HD4000 / i915 Ivybridge
- Mesa 18.3.1
- xf86-video-intel 1:2.99.917+855+g746ab3bb
- GL_VERSION: 3.0 Mesa 18.3.1
nvidia GeForce 740M
- bumblebee 3.2.1
- Proprietary nvidia 415.25
- GL_VERSION: 4.6.0 NVIDIA 415.25

Blender Version
Broken: a712fbda6a to a6e6ad0756 at least

Short description of error
When running on Intel HD / i915, UV editor shows an extra edge per ngon going from any of their edges to (0, 0)

There is nothing at (0, 0), no point can be selected.

Running on nvidia gives correct output:

Exact steps for others to reproduce the error

Open any file with a UV-mapped object
Go into edit mode
Open UV editor

This is probably due to an incorrect GL buffer item count in the draw commands, or a bug with the vertex assembly mode used to draw the points and edges in the driver.

**System Information** Arch Linux * Linux 4.20.2-1-ck-ivybridge * Intel i5-3317U w/ Intel HD4000 / i915 Ivybridge * Mesa 18.3.1 * xf86-video-intel 1:2.99.917+855+g746ab3bb * `GL_VERSION`: 3.0 Mesa 18.3.1 * nvidia GeForce 740M * bumblebee 3.2.1 * Proprietary nvidia 415.25 * `GL_VERSION`: 4.6.0 NVIDIA 415.25 **Blender Version** Broken: a712fbda6a17 to a6e6ad07563738b641c9df9e8c48ec0cf9342068 at least **Short description of error** When running on Intel HD / i915, UV editor shows an extra edge per ngon going from any of their edges to (0, 0) ![Screenshot_2019-01-22_19-49-50.png](https://archive.blender.org/developer/F6370284/Screenshot_2019-01-22_19-49-50.png) There is nothing at (0, 0), no point can be selected. Running on nvidia gives correct output: ![Screenshot_2019-01-22_19-53-26.png](https://archive.blender.org/developer/F6370381/Screenshot_2019-01-22_19-53-26.png) **Exact steps for others to reproduce the error** 1. Open *any* file with a UV-mapped object 1. Go into edit mode 1. Open UV editor This is probably due to an incorrect GL buffer item count in the draw commands, or a bug with the vertex assembly mode used to draw the points and edges in the driver.

Celeste Wouters commented

2019-01-22 19:59:33 +01:00

Added subscriber: @ElementW

Celeste Wouters commented

2019-01-22 21:41:45 +01:00

After some digging it appears the driver chokes on primitive restart indices; the index buffer for the UV map of the default scene cube is
0 1 2 3 0 255 4 5 6 7 4 255 8 9 10 11 8 255 12 13 14 15 12 255 16 17 18 19 16 255 20 21 22 23 20 255 where 255 is set as restart marker.
The weird thing however is if I get the index buffer content (to get the data above) using glGetBufferSubData, restart markers start working correctly and ghost edges disappear. Will investigate further as this is very likely the sign of a driver bug.

After some digging it appears the driver chokes on primitive restart indices; the index buffer for the UV map of the default scene cube is `0 1 2 3 0 255 4 5 6 7 4 255 8 9 10 11 8 255 12 13 14 15 12 255 16 17 18 19 16 255 20 21 22 23 20 255` where `255` is set as restart marker. The weird thing however is if I get the index buffer content (to get the data above) using `glGetBufferSubData`, restart markers start working correctly and ghost edges disappear. Will investigate further as this is very likely the sign of a driver bug.

Jacques Lucke commented

2019-01-23 11:54:45 +01:00

Added subscriber: @JacquesLucke

Jacques Lucke commented

2019-01-23 11:54:45 +01:00

Changed status from 'Open' to: 'Archived'

Jacques Lucke closed this issue

2019-01-23 11:54:45 +01:00

Jacques Lucke self-assigned this 2019-01-23 11:54:45 +01:00

Jacques Lucke commented

2019-01-23 11:54:45 +01:00

Blender 2.8 requires at least OpenGL 3.3.
Looks like your intel only supports OpenGL 3.0.

https://www.blender.org/download/requirements/

Blender 2.8 requires at least OpenGL 3.3. Looks like your intel only supports OpenGL 3.0. https://www.blender.org/download/requirements/

Celeste Wouters commented

2019-01-23 13:27:43 +01:00

@JacquesLucke The reported GL_VERSION is wrong actually, it's the output given by glxinfo for a non-core context and Mesa (at least for Intel) acts conservatively when asking for a GL context and reports the lowest version possible matching the requested context settings, which here is 3.0. Asking for a core context yields 4.2 (Core Profile) Mesa 18.3.1 but all the required extensions up to 4.2 are still accessible with lower versions.

Forcing GL 3.[012] using MESA_GL_VERSION_OVERRIDE=3.x Blender refuses to run with a Blender requires a graphics driver with at least OpenGL 3.3 support. message anyway.

Keep that bug closed. It's definitely a problem on Mesa's side related to either buffer invalidation or GL state tracking when drawing with GL_LINE_STRIP.

@JacquesLucke The reported `GL_VERSION` is wrong actually, it's the output given by `glxinfo` for a non-core context and Mesa (at least for Intel) acts conservatively when asking for a GL context and reports the lowest version possible matching the requested context settings, which here is 3.0. Asking for a core context yields `4.2 (Core Profile) Mesa 18.3.1` but all the required extensions up to 4.2 are still accessible with lower versions. Forcing GL 3.[012] using `MESA_GL_VERSION_OVERRIDE=3.x` Blender refuses to run with a `Blender requires a graphics driver with at least OpenGL 3.3 support.` message anyway. Keep that bug closed. It's definitely a problem on Mesa's side related to either buffer invalidation or GL state tracking when drawing with `GL_LINE_STRIP`.

andrii simiklit commented

2019-01-30 13:02:08 +01:00

Added subscriber: @asimiklit

andrii simiklit commented

2019-01-30 13:02:08 +01:00

Hi all,

Could somebody re-check the issue with attached mesa patch and confirm if it helps?
v2 of 0001-i965-remit-index-buffer-state-on-prim_restart.enable.patch

Thanks,
Andrii.

Hi all, Could somebody re-check the issue with attached mesa patch and confirm if it helps? [v2 of 0001-i965-remit-index-buffer-state-on-prim_restart.enable.patch](https://archive.blender.org/developer/F6453069/v2_of_0001-i965-remit-index-buffer-state-on-prim_restart.enable.patch) Thanks, Andrii.

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Extra ghost edge per ngon in UV editor on Intel HD gfx #60762