Vibrant Visuals draws a stray line next to hard steps in block heightmap

SUMMARY

Vibrant Visuals draws a thin stray line next to hard steps in a block heightmap; it is much weaker or absent when the colour texture is flat or blurred at the step.

DESCRIPTION

In a resource pack with the pbr capability, a block whose texture set has a heightmap with a hard step (for example 0 beside 255, or a 255 square on a 127 base) shows a thin extra line near the step edge in Vibrant Visuals. The line is not in the heightmap. It sits about one texel from the real edge, is seen on one face orientation more than the other, and can look dashed. Blocks with a flat heightmap (all 0, all 127 or all 255) show no line. The same heightmap with a flat colour texture shows only a faint dashed outline at the step, and with a colour texture blurred by one texel across the step the line is not visible. The tiles are 32x32 unless stated.

Steps to reproduce

1. Import the supplied world.

2. Turn on Vibrant Visuals in Video settings.

3. Go in-game.

4. Sample blocks are set up with the heighmap used for each shown below.

5. Otherwise, Open the Creative inventory, Construction tab, and take BV Island (twf_ph:bv_island), BV Ring 0 In 255 (twf_ph:bv_ring0), BV Island Flat Colour (twf_ph:bv_island_fc) and BV Island Soft Colour (twf_ph:bv_island_soft). Place them a few blocks apart in the open, in daylight.

6. Walk/fly around each block and look at all four sides, close up and at an angle.

Observed result

• BV Island and BV Ring 0 In 255: a thin line appears just beside the step edge, offset from it, on one face orientation.

• BV Island Flat Colour: only a faint dashed outline at the step.

• BV Island Soft Colour: no visible stray line.

• Higher resolution (128x128 color texture and heightmap) makes it thinner, but it never disappears.

Expected result

The step should be drawn once, at the position the heightmap gives, with no second thin line offset from it, whatever the colour texture does at that edge.

Additional notes

• Heightmaps in the test blocks use only the values 0, 127 and 255 (single channel, 8-bit).

• Flat heightmaps (0, 127, 255) show no artifact, so this is not an edge-of-tile issue.

• Mip levels: num_mip_levels 0 in terrain_texture.json made the artifact a little fainter on one block but did not remove it.

• Possible cause: the relief shifts the colour lookup at a step, so a hard colour edge on the same step exposes a sliver of the wrong colour.