Triangulated fill outlines

[stefankarschti]

feat: Fill layer to generate outlines composed of triangle primitives

• Created a new addition to the fill generator functions to generate this new fill+outline variant
• The Fill bucket generates fill outlines with triangle primitives, compatible with the Line shader
• The Fill bucket uses gfx::generateFillAndOutineBuffers to generate its buffers
• Added an option to enable/disable this feature at compile time with the MLN_TRIANGULATE_FILL_OUTLINES #define in fill_bucket.hpp

Refs: #1768

[stefankarschti]

WIP

[stefankarschti]

Comparison of fill outlines

Legacy renderer:

Drawable renderer (width=2):

Metal renderer (width=1):

[stefankarschti]

Fill pattern outline drawn with the legacy renderer:

And with the Metal renderer (no outline):

[github-actions]

Bloaty Results 🐋

Compared to main

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  +0.5%  +749Ki  +0.4%  +128Ki    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results/pr-1780-compared-to-main.txt

Compared to d387090 (legacy)

    FILE SIZE        VM SIZE    
 --------------  -------------- 
   +20% +22.8Mi  +404% +24.1Mi    TOTAL

Full report: https://maplibre-native.s3.eu-central-1.amazonaws.com/bloaty-results/pr-1780-compared-to-legacy.txt

[louwers]

Why is the MLN_TRIANGULATE_FILL_OUTLINES flag needed? Is it only because the legacy renderer does not support it? In this case, please add a comment to the issue to remove the legacy renderer to remove this build flag as well.

In general, I think we should avoid build time configuration as much as possible because only the default is tested / compiled on CI.

[stefankarschti]

@louwers : I added that flag following Steve's recommendation to "provide an option to turn that off and use Metal lines"...
CC @sjg-wdw

[sjg-wdw]

@louwers : I added that flag following Steve's recommendation to "provide an option to turn that off and use Metal lines"... CC @sjg-wdw

Nice!

[alexcristici]

There are 13 render tests that are passing now with #define MLN_TRIANGULATE_FILL_OUTLINES 1. 👍

But render test render-tests/fill-outline-color/property-function is drawing white background, before it was drawing ok but failing because of line width.

Before:

After:

[louwers]

Should we make the more correct (less performant) version the default?

@sjg-wdw @stefankarschti Can one of you create an issue that links to this PR to re-address this after variants have been introduced?

[stefankarschti]

While investigating the failed render tests I realized that we also need shader variations for the triangulated lines in case of outline-color and opacity per-vertex, which is the case with some expressions.
render-tests/fill-outline-color/zoom-and-property-function
render-tests/fill-outline-color/property-function
ref #1855