Graphical artifacts with antialiased lines in OpenGL

[Robert Rojas]

On Ubuntu 16.04.3, as from the update fixing https://bugs.launchpad.net/ubuntu/+source/mesa/+bug/1735594, antialiased line rendering in applications using Opengl is corrupt. Experienced using Intel GM45.

Steps to reproduce:
1) Create an OpenGL application.
2) Enable GL_LINE_SMOOTH and set line width to any value below 1.5.
3) Draw a line (either by shaders or by glBegin).

Blender and various games by Kenta Cho (tumiki-figthers, torus-trooper, parsec47, titanion) are affected.

[Timo Aaltonen (tjaalton)]

So you mean mesa 17.2.x is buggy? Please test 17.3.3:

https://launchpad.net/~ubuntu-x-swat/+archive/ubuntu/updates

is the bug hw/driver specific?

[Robert Rojas (roberthrojasq)]

Tested 17.3.3, no success.

The artifacts appeared after the #1735594 fix, so they may be specific to i965. My computer graphics indicate "Mobile Intel® GM45 Express Chipset".

I found that the game titanion looks as expected when the window is resized to 960x720 or greater. Inspecting the source I found the game adjusts the line width at window resize while the other games keep it at 1 or 2, so I believe the driver is drawing the lines thinner than it should.

[Timo Aaltonen (tjaalton)]

can you test bionic?

[Robert Rojas (roberthrojasq)]

Tested Bionic daily 20180321 in a live session, still happens.

[Timo Aaltonen (tjaalton)]

and how about cosmic/18.10?

if it's still buggy, you'll need to file this upstream

[Timo Aaltonen (tjaalton)]

I'm assuming this is fixed in mesa 18.2.2 in cosmic, which also landed bionic last night

if not, feel free to reopen