Huge lag when smoke / semi-transparent / alpha effect

[eddiefur]

I don't understand why games lag so much when there is too much semi-transparent polygons on the screen. My computer run at max speed every games in a normal scene, but when semi-transparent polygons start to take a lot of place on the screen, games start to lag ridiculously. In my head, polygons are polygons and textures are textures, it's all the same, but I see that it's not the case. Is there a way to fix or disable those semi-tranparent alpha laguish polygons?

Thanks!

[[Unknown]]

PSP games often use alpha testing, which modern hardware doesn't like. Modern games don't use alpha testing anymore, it's considered an outdated technique.

Additionally, the PSP supported complicated alpha blending modes, which modern hardware does not natively support. Sometimes we have to do extra work to emulate these correctly. You can check "Disable slow framebuffer effects" in the settings to disable this extra effort - but it may make it look bad.

What game or games is this even happening in?

-[Unknown]

[eddiefur]

Thanks for the reply!

I wanted to share a screenshot but It seems we are unable to upload photo to the forum.

Anyway, I will tell you a place it's always happening.

Lego star wars II, the US version. If you go into the first level of episode VI, in the cutscene, when the spaceship door opens, you'll see darth vader and a bunch of smoke (aka semi-transparent textures). Before the door opens, I'm at 60fps 100%. But when the smoke are all over the screen, I'm at 23 fps 36.9%. When the smoke disappear, I'm back at full speed 60 fps.

This happens all the time in every games where semi-transparent textures takes a lot of place on the screen. If it's just a little semi-transparent object or effect, it'll be ok, but when they are all over the place, it's a nightmare .

I checked the option "disable slowers effect" but there is no difference, the same lag happens.

[[Unknown]]

Hmm, try unchecking "simulate block transfer" then? This will also disable a bunch of effects.

But if neither of those help, that's interesting. I don't own that game, so I don't know what effect it's using exactly.

If you're on Windows and want to dig into it a bit, try finding the fog with this:
https://github.com/hrydgard/ppsspp/wiki/...E-debugger

Personally, I think you'll find it interesting to just see how the game draws things. Try to step until you see the clouds on the left side, and the area where the clouds end up highlighted in red. A screenshot of the debugger there would help me understand what effect it's using that's slow (you can post a link by not having http:// and splitting up the domain a bit, like "www google com /search".)

Also you can post links after some rules are met, maybe just a min # of posts. So maybe you will be able to now already.

-[Unknown]

[eddiefur]

OK! I will check that after the new year festivities! Thank you!

[eddiefur]

Um... I checked it out with the GE Debugger and it can't be the smoke texture that makes the lag. It appears to be only one plane with an animated texture on it. I tried other games with lot of alpha textures and there is no problem. I think the real problem is that some time, the camera is far away and show a big scene and the polycount start to grow very high. Maybe you developpers could add a hack for slow computer like mine : a mist hack. If the polygon is farther than x distance from camera, then don't draw polygon. Maybe it could fix the lag... But it's just a theory of mine.