08745: starcas: Invisible projectiles on OpenGL backend

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
08745	Graphics	Minor	Always	Aug 12, 2023, 14:08	Aug 23, 2023, 11:30

Tester	AJR	View Status	Public	Platform	MAME (Self-compiled)
Assigned To	AJR	Resolution	Fixed	OS	Linux (64-bit)
Status [?]	Resolved			Driver	cinematronics/cinemat.cpp
Version	0.255	Fixed in Version	0.258	Build	64-bit
		Fixed in Git Commit	4727a73	Github Pull Request #

Summary	08745: starcas: Invisible projectiles on OpenGL backend
Description	When the player's ship fires, the projectiles are invisible. This is a regression since 0.248, where they appeared as blue points. I experimentally reverted 4df2f9d2f904073cd31d4d5db65cdb0d23270aac for ccpu, but that didn't fix this. It seems to be a purely graphical glitch, as the game remains otherwise playable.
Steps To Reproduce	Start a game and start firing at anything.
Additional Information	This seems specific to the OpenGL backend. With -video bgfx, dots can be seen at the ends of vectors, which also appear in my 0.248 build.
Github Commit

Flags
Regression Version
Affected Sets / Systems	starcas

Attached Files

No.21696 Haze Senior Tester Aug 12, 2023, 15:31	I can still see (very dark) blue points here
No.21699 Robbbert Senior Tester Aug 15, 2023, 08:53	The bullets show up clearly for me.
No.21700 AJR Developer Aug 15, 2023, 23:44	With -video bgfx, the end dots return. I'll mark this report as OpenGL specific.
No.21702 hap Developer Aug 16, 2023, 19:41	opengl ignores mame.ini beam_dot_size somehow? set eg. beam_dot_size 5.0 then try in another video backend, get huge dots in starcas. try with opengl and they're near invisible as you say.
No.21703 Robbbert Senior Tester Aug 17, 2023, 04:57	Confirmed with opengl. Also, when the player's ship blows up there's no debris.
No.21707 AJR Developer Aug 19, 2023, 19:14 edited on: Aug 19, 2023, 19:16	After further investigation of the OpenGL renderer, I was able to locate the code that fails to respect -beam_dot_size (whose value is actually instated by the "vector" video device). However, this also points to a flaw in OpenGL itself regarding the GL_POINT_SMOOTH feature, which MAME automatically enables. Antialiasing and "proper filtering" are great things to have in theory, but in practice the OpenGL drivers draw "smooth" point objects as circle shapes that are smaller than they would be with the feature disabled (which turns them into squares) or with other renderers (BGFX draws them as diamonds) and vanishingly faint with the default -beam_dot_size. What's more, this flaw is unlikely to ever be fixed, given that the "Fixed Function Pipeline" OpenGL API that MAME uses was already deprecated when SDLMAME (where the OpenGL renderer originated) was merged in 2010. (The newer, shader-based OpenGL API appears to not even include GL_POINT_SMOOTH.) The easiest recourse to the OpenGL dot size problem, I think, would be to just disable GL_POINT_SMOOTH. Are there any objections to that?
No.21708 hap Developer Aug 19, 2023, 19:52	I don't see any difference when I locally remove GL_POINT_SMOOTH. The Windows GDI renderer also doesn't like it if you increase beam_dot_size btw, it will draw thin vertical lines.