Trunk_link flickering in car navigation with perspective mode (Vulkan only) about organicmaps HOT 10 OPEN

I think its related to #891.

Thick lines consist of square segments and circles at their ends/joins. Segments and circles have the same depth value, which causes z-fighting.

FYI @vng

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This is the nearest reason here :)
af37c06

from organicmaps.

I suppose we will be struggling a lot with the transparent bridges :)

from organicmaps.

This is the nearest reason here :) af37c06

Hm, how could it possibly affect this?
This change is present in the May release only, while the OP says flickering has started in February. Also there are no bridge areas at this intersection.

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It is a guess honestly, should check manually.

I talked to a guy who worked with drape before and he says that drawing areas is not a simple/straightforward routine taking into account 3D perspective - true geometry depth added, not only Z-order.

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UPD: I've double-checked and areas don't influence here.

@pastk I found some strange colors (suspect for different link opacity) and can't understand where these colors come from (motorway_link colors should be equal with motorway according to mapcss):

vehicle_light:

motorway:

  element {
    scale: 19
    lines {
      width: 37.0
      color: 1307964388
      priority: 249
      cap: BUTTCAP
    }
    lines {
      width: 34.0
      color: 16748864
      priority: 250
    }

motorway_link:

  element {
    scale: 19
    lines {
      width: 26.5
      color: 1307964388
      priority: 167
      cap: BUTTCAP
    }
    lines {
      width: 24.0
      color: 1308594496    // <-- This
      priority: 168
    }

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We have double line drawing (casing/core ?) in vehicle style (don't know why) and seems like with a different opacity.
While the default style has one rule for motorway/_link.

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We have double line drawing (casing/core ?) in vehicle style (don't know why) and seems like with a different opacity. While the default style has one rule for motorway/_link.

Yeap vehicle style uses casing / outlines for bigger roads. The casing line has lower priority so shouldn't cause z-fighting.

And motorway_link's opacity is lower than of motorway, so that its less prominent. It had been like this for a long time..

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I did a manual check:

• 2023.12.20-4-android - NO bug
• 2024.01.09-5-android - bug EXISTS

Looks like it was introduced with a transparent motorway_link color. At least I see the same with motorway (NOT transparent) color in the December release, and the transparent color in the January release (for the default style, and in the vehicle too I suppose).

from organicmaps.

Looks like it was introduced with a transparent motorway_link color. At least I see the same with motorway (NOT transparent) color in the December release, and the transparent color in the January release (for the default style, and in the vehicle too I suppose).

It looks like adding transparency just made the bug visible, though is existed before.

If a line section is semi-transparent and then a circular semi-transparent join is overlapped then their intersection will obviously look less transparent / more bright. So a line will inherently look patchy anyway.

The bug is those "patchy" areas are not "stable" in vulkan case.

It might be possible to change "joins" shader or program to discard a fragment if its the same depth as in the depth buffer already (meaning there is an underlying line section quad already).

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