Glowmaps fail on open-source Radeon driver

[Luomu]

Got a report on IRC from an Arch Linux user.
Couple of screenshots that show the situation quite well:

Looks like glowmap (only used on the new buildings) is somehow bound on texture slot 0, which is why it appears on the eagle as well.

It apparently works with the proprietary driver.

The driver version is.
xf86-video-ati
6.14.2-2

[Luomu]

I now reproduced the situation in Ubuntu/gallium driver.

[robn]

I've also managed to reproduce this on VMware Workstation 8 running Windows 7 64-bit (on Linux x86_64 with proprietary NVidia drivers). This was after starting the game and returning to the menu:

Amusingly I may have known about this for a while. The models have always been "black" under VMware, but I always assumed that was due to deficiencies in its drivers. Perhaps we're actually doing something slightly wrong that some drivers can cope with (like the Radeon HDR shader thing we had a while back)?

[Luomu]

I poked at this for a while. If you want to workaround this, comment out lines

if ( useglow )
    emission = texture2D(texGlow, gl_TexCoord[0].st);

in data/shaders/model.frag.glsl and at least you'll have textures back. I did not, however, manage to fix this. Just sampling that second texture messes up the result, and it seems like a branching problem as well. That if(useGlow) bit is always run. Setting the condition "if (false)" works - but it could be that it's then optimized out.

So, problems with multiple textures perhaps. HDR mode doesn't work either on these drivers, but it's a bit more complicated. Even basic multitexturing like this doesn't work:

uniform sampler2D Texture0;
uniform sampler2D Texture1;

void main(void)
{
   vec4 one = texture2D(Texture0, gl_TexCoord[0].st);
   vec4 two = texture2D(Texture1, gl_TexCoord[0].st);
   gl_FragColor = mix(one, two, 0.5); // equivalent to (one * 0.5) + (two * 0.5)
}

I always get only the second texture.

Things to do:

• try bleeding edge drivers
• come up with a shader organization where we can turn off individual graphical features without relying on branching - turning off shaders entirely is a bit of an excessive workaround.

[jaj22]

While testing various stupid ideas on VMware, I discovered that this only happens when the main texture is bound to texture unit 0. Other combinations such as tex 1, glow 0 or tex 1, glow 2 work fine.

I'm not happy to put this down to a driver bug when there are so many that exhibit the same symptoms, but I'm struggling to think of any way that Pioneer could cause it.

[Luomu]

I tried to reduce the test case even further: 3c6afef672c019e016bee10331e14d1ed195e22c

Blending a red & blue texture, on FGLRX it works (disregard the blue tint, it came from the compiz screenshot tool):

On whatever free drivers Ubuntu offers by default, GLSL works but only one texture is visible:

After the workaround above, using texture units 1 & 2 it blends OK:

Weird.

[jaj22]

That's now four days I've wasted tracking down bugs (this is the second) in that goddamn multi-line #define.

[robn]

Do you know where tomm lives? :)