Change image_lodbias default value

[markanini]

Changing the image_lodbias value from default "0" to "-0.3" improved the appearance of railings and diamond meshes for me to a point where it became a mainstay of my Dhewm3 config. I experimented with various values over a long period granularly and I'm fairly certain that this is an optimal value visually.

[drewwoods]

Do you have comparison screenshots at maybe high and low resolutions? Would be nice to add to justify the change

[markanini]

-0.3 - Note the meshing in from of the ceiling lights is better defined Default - Note the meshing in front of the ceiling lights is muddy and partially absent -0.3 - Note the corner directly in front is better defined Default - Note the corner directly in front is blurred -0.3 - Note the central control panel is better defined Default - Note the central control panel is blurred

It's somewhat hard to convey in still images, easier to see in motion. But default comes off somewhat artificially blurred, and faint details such as diamond meshes and railings get muddy disappear at a distance prematurely. -0.3 addresses this without really looking over sharpened or more significantly more aliased than default.

[drewwoods]

Thanks for putting together the screenshots, that definitely helps.

Full disclosure: I don't have a strong preference here and I am not a contributor. My earlier comment was mainly to encourage providing concrete evidence so the suggestion does not get lost among subjective "I prefer X" opinions.

My main pushback is: if -0.3 is objectively better, why did id Software not ship it that way? It is possible that, at the common resolutions of the time, 0 simply looked better. It also raises the question of whether this setting should actually be resolution dependent rather than a single global default.

To be honest, I still find the difference hard to see in these still frames. As you mentioned, motion might make it more obvious. The screenshots are subtle enough that zooming helps, so I zoomed the first comparison for clarity.

As an alternative to changing the default outright, it might be more useful to propose a small tuning guide: what these settings control, what the tradeoffs are, and how players can adjust them based on hardware and resolution. These options exist because they are preferences and easy for users to tweak. Improving discoverability may be more valuable than changing the default.

First comparison

Default:

-0.3:

[markanini]

I suppose Doom 3 was tuned for 2004 era hardware where lower resolutions would make minor aliasing more apparent, favoring blurrier textures. I think a good spot to view the effect of granular image_lodbias values is the platform ride in Alpha Labs - Sector 4 when you choose the ERF system, seen in this walkthrough at 19:23 https://youtu.be/encT6edW01Y?si=r_A0PVaq5RTEU60a&t=1163
You could raise image_lodbias value to -0.4 or -0.5 for even more sharpness, but -0.3 avoids increasing visible aliasing too much, while being sharper than default 0, a good sweet-spot IMHO. My monitor is 24" at 1920x1080 native, yielding a 92 PPI. For someone with for instance a 27" 2560x1440 monitor the 109 PPI might be high enough to where an image_lodbias value lower than -0.3 might work, but image_lodbias -0.3 should be a good conservative value that works on common lower PPI displays used in 2025.