Implementation for BENTLEY_materials_line_style

[danielzhong]

Fixes #8836

This PR adds support for the proposed BENTLEY_materials_line_style glTF extension. The proposed specification can be found here.

This PR introduces support for the BENTLEY_materials_line_style extension in glTF. iTwin.js can now interpret and render line primitives with their specified width and pattern properties when loading glTF files. glTF materials can now specify a line width plus a 16‑bit dash bitfield, and we’ll map it either to one of the legacy LinePixels codes or dynamically append a fresh pattern to the shared line-code texture (which now auto-expands beyond the original 10 entries and reloads on demand)

To test this branch:

1. Clone itwinjs-core
2. Build test-apps/display-test-app
3. Run display-test-app
4. Open blank connection

5. In the keyin field in the top left, enter the keyin: dta gltf

6. Within the file open dialog, open test file line_style.zip

Find the following section in the material definition:

"extensions": {
        "BENTLEY_materials_line_style": {
          "width": 3,
          "pattern": 61694
        }
      }

Then, modify the width and pattern values as you like.

iTwin default line pattern values:

Line Style (LinePixels)	16-bit Pattern	JSON / Decimal	Description
Solid	0xFFFF	65535	Solid line
Code1	0x8080	32896	1 on, 7 off (dotted)
Code2	0xF8F8	63608	5 on, 3 off
Code3	0xFFE0	65504	11 on, 5 off
Code4	0xFE10	65040	7 on, 4 off, 1 on, 1 off
Code5	0xE0E0	57568	3 on, 5 off
Code6	0xF888	63624	5 on, 3 off, 1 on, 3 off, 1 on, 3 off
Code7	0xFF18	65304	8 on, 3 off, 2 on, 3 off
HiddenLine	0xCCCC	52428	Hidden line (2 on, 2 off)
Invisible	0x0001	1	Invisible line

More customize example:

Custom Pattern	Decimal (JSON)	Binary (LSB → MSB)	Description
0x0F0F	3855	1111000011110000	4 pixels on / 4 pixels off (even rhythm)
0x00FF	255	1111111100000000	8 pixels on / 8 pixels off (long bright segment)
0xC003	49155	1100000000000011	2 on, 12 off, 2 on — isolated short bright spots
0xF0FE	61694	1111111000001111	4 long on, then alternating short on/off — “long–dot-dot” pattern
0xAA55	43605	1010101001010101	Alternating 2 on / 2 off — faster rhythm than the default dotted line (0xAAAA)

Display.Test.App.2025-12-11.15-48-20.mp4

[mergify]

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[Copilot]

Pull request overview

This PR implements support for the proposed BENTLEY_materials_line_style glTF extension, enabling iTwin.js to render line primitives with custom widths and patterns from glTF materials. The implementation introduces a dynamic line code texture system that can expand beyond the original 10 predefined patterns to accommodate custom patterns defined in glTF files.

Key changes:

• Added glTF schema and parser support for the BENTLEY_materials_line_style extension with width and pattern properties
• Refactored the line code system from static 10-pattern texture to dynamic pattern registration supporting up to 256 patterns
• Implemented automatic texture reloading when new patterns are registered at runtime

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
core/frontend/src/tile/GltfReader.ts	Adds parsing logic for the line style extension, mapping glTF patterns to LinePixels codes and applying them to DisplayParams
core/frontend/src/test/render/webgl/LineCode.test.ts	Updates test expectation to reflect dynamic pattern assignment instead of fallback to solid
core/frontend/src/internal/render/webgl/glsl/Polyline.ts	Updates shader code to use dynamic capacity constant instead of hardcoded texture height
core/frontend/src/internal/render/webgl/Texture.ts	Exports Texture2DCreateParams class to enable texture reloading from System
core/frontend/src/internal/render/webgl/System.ts	Implements texture reload mechanism with event listener for dynamic pattern updates
core/frontend/src/internal/render/webgl/LineCode.ts	Replaces static pattern data with dynamic texture generation using shared pattern registry
core/frontend/src/common/internal/render/LineCode.ts	Implements core pattern registration system with Map-based lookup and event notification
core/frontend/src/common/gltf/GltfSchema.ts	Defines TypeScript interface for the BENTLEY_materials_line_style extension

[pmconne]

Do you intend to simultaneously enhance the tileset publisher to output this extension, so you can test both sets of changes against one another? Or will you do that later and submit a new PR for any decoding/rendering issues discovered afterward?

[pmconne]

Why specifically 256?

[danielzhong]

It's just a random number. Do you have any suggestions for what a reasonable value would be?

[pmconne]

Well the maximum number of possible unique patterns is 65,536, right? And the maximum height of the texture is given by System.maxTextureSize. It will be less than 65,536, but far more than 256 (typically, 16k). So, no more than the max texture size. (You could of course put more than one pattern on each row of the texture to get around that, but realistically you will never need that many).

[danielzhong]

Do you intend to simultaneously enhance the tileset publisher to output this extension, so you can test both sets of changes against one another? Or will you do that later and submit a new PR for any decoding/rendering issues discovered afterward?

I prefer to do that later and follow up with a separate PR if any decoding or rendering issues come up.

[mergify]

This pull request is now in conflicts. Could you fix it @danielzhong? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

[danielzhong]

I have verified the encoding works perfectly with this PR decoding. I also confirmed that both default and non-default line patterns render correctly.

FYI: @pmconne

[danielzhong]

Added a fix for BENTLEY_materials_point_style. The issue was not caused by this PR; it already exists on the main branch.

FYI: @markschlosseratbentley

[mergify]

This pull request is now in conflicts. Could you fix it @danielzhong? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

[Copilot]

Pull request overview

Copilot reviewed 14 out of 15 changed files in this pull request and generated 3 comments.

[mergify]

⚠️ The sha of the head commit of this PR conflicts with #8922. Mergify cannot evaluate rules on this PR. ⚠️