Problems with sky (maybe Matrox G-series specific)

[Sledgedog]

Hello

In the hope that someone might have found a solution to the same problem before me...

I have two machines running linux. One has a 32MB Matrox G400 MAX, and another has a 16MB G400. Both have the same problem with rendering the background picture a.k.a. sky.

It seems like only the topmost "row" of the sky is drawn. The default is 3 rows. All other "rows" do not exist on screen, and edges of buildings (and menus and the console) leave traces on the area where the sky should be.

By doins "skyrows 1" I can extend the sky down to the level of the horizon. But then most of it is one-colored (pale gray in E1M1), with the exception of one quadrant.

With "simple sky" on and skydetail 1, I can see one fourth of the sky, i.e. the sky bitmap extends from the "west" of the automap to "north." Other 270 degrees stay pale gray.

With "simple sky" off and skydetail 1, the sky image starts from "west" but fades to pale gray before "north."

With skydetail 2, the visible "sky" is narrowed to 45 degrees, from "west" to "northwest." The sky image is not squeezed or scaled, just clipped. Vertically it is ok as long as "skyrows" is 1. With "skydetail 10" I see only 9 degrees of the sky, and so on.

Doomsday version is 1.8.6, and my other settings must be ok since I have a third machine that has identical setup with the one that has the 16MB Matrox, and it has a perfectly working sky. Only difference is that the third machine has a GeForce 2MX.

This is not a regression. The problem has been with me for as long as I can remember. Maybe the first version of Doomsday for linux didn't have this, but I'm not sure. I also don't know if xorg 6.8.0's OpenGl implementation has a bug here.

[skyjake]

It could be caused by something weird in the G400 OpenGL drivers.

Try this, though. Open the monstrous gl_tex.c and insert these two lines into GL_PrepareSky2 (probably around line 2508):

gl.TexParameter(DGL_WRAP_S, DGL_REPEAT);
gl.TexParameter(DGL_WRAP_T, DGL_REPEAT);

They should go after the other TexParameter calls.

[Jimi]

Matrox sucks, very bad OpenGL support. I would just take the Matrox cards away from the computers and smash them with a hammer or my foot.

[The Undertaker]

But they have good 2D.

[Jimi]

But that's not enough. There's too much 3D out there, Matrox can't handle it and explodes.

[Zach Keene]

Originally Posted by Sledgedog

I also don't know if xorg 6.8.0's OpenGl implementation has a bug here.

It may well be xorg. I tried it a month or so back with whatever version of Doomsday was current then, and had pretty much the same problem (whole sky is a HOM). Except I'm using a 32MB ATI All-in-Wonder 128.

Switching back to XFree set everything back to normal, but since then Gentoo has pretty much decided that we either switch to xorg or don't update anything, so now I'm stuck with the HOM-sky again.

Upgrading to lastest CVS (which already has the fix skyjake posted above) hasn't helped, but then I don't think this is Doomsday's fault anyway.

EDIT: yup, I'm having the exact same problem as the original poster. At least 'skyrows 1' gets rid of the annoying HOM effect...

[sekhmet]

I just ran into this myself. I haven't tested every single combination of parameters listed in the first post, but so far all of them are behaving as-described.

My graphics card is an Intel i915GM (this is on a laptop), using the i810 driver from Xorg 7.0RC0 (support for the i915GM isn't available in any officially-released X yet), so the problem's not specific to Matrox.

I haven't tried the patch suggested in the second comment yet; I'll do that later today. Just wanted to see if anyone's got any other ideas.

[Zach Keene]

Originally Posted by sekhmet

I haven't tried the patch suggested in the second comment yet; I'll do that later today.

You probably are, actually, since that patch was placed in the Doomsday code a while back.

Out of curiosity, do you have xscreensaver installed, and if so, do you get graphic corruption with some of the GL screensavers? (AntSpotlight, Pipes, and Moebius distort badly for me.) That's something else I've noticed going wacky since switching to xorg.