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GFX_OPTIONS.md

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Graphical quality options

Variables and locations that can be changed or exposed as options to improve graphical quality, increase details and effects, etc.

Shipped options

All three are off by default, so a stock run renders exactly as before. None of them has a menu entry yet; set them from the console or the config file.

Option Console lba2.cfg Environment Values
Texture filtering gfx_texfilter TextureFilter LBA2_TEXFILTER 0 off, 1 horizontal 2-tap, 2 bilinear 4-tap
Dithered shading gfx_dither DitherShading (none) 0 off, 1 on
Interior render scaling (none) (none) LBA2_ISO_DIV 1 off, 2 to 4

Texture filtering smooths magnified texels on terrain, sea, and sky. The rasterizer works in palette indices, where averaging two entries is meaningless, so the blend is a precomputed table of the nearest palette index to each 25/50/75% RGB mix. Costs roughly 7% of frame time on terrain and 4% on a sea-heavy view at 1728x1080 with the 4-tap setting.

Dithered shading applies an ordered dither to Gouraud shade rows, which softens the 16-step banding of the original palette ramps.

Interior render scaling renders isometric interiors at 1/N of the chosen resolution and lets the present stretch them back, so the room is drawn larger. Nothing in an interior scales with the framebuffer (bricks are pre-rendered sprites and the iso projectors take no focal argument), so a bigger framebuffer otherwise just reveals more empty space around the room: it covers 29% of the frame at 1728x1080 against 82% at 640x480. Exteriors, whose projection does carry a focal, always render at full resolution.

LBA2_ISO_DIV is read once at startup and cannot be changed mid-run. It is also ignored when the divided size would fall below the engine's 320x200 minimum, which is silent: at 640x480 a divisor of 2 works and 3 does nothing.

LBA2_ISO_DIV=2 ./lba2cc

Ideas not yet wired up

  • DetailLevel and Shadow are stored in lba2.cfg and exposed via the Options menu; see CONFIG.md for the full key list.
  • RAIN_RANGE in SOURCES/3DEXT/LINERAIN.ASM controls how far the rain effect is drawn in the original ASM implementation.
  • In the community build, the rain line routine is compiled from SOURCES/3DEXT/LINERAIN.CPP by default; the ASM file is kept for historical reference. If you want a user-facing option for rain draw distance in modern builds, consider wiring it through the C++ implementation rather than only tweaking the ASM constant.