Add background_color to CameraCfg for cross-backend solid color camera backgrounds

[mataylor-nvidia]

Description

• Adds CameraCfg.background_color: tuple[float, float, float] | None — normalized RGB floats in [0, 1], defaulting to None (preserves existing per-backend defaults).

• Wires the setting through all three renderer backends:

  • Newton (NewtonWarpRenderer): converts to ARGB uint32 and passes as SensorTiledCamera.ClearData.clear_color.
  • OV RTX (OVRTXRenderer / build_render_scope_usd): authors omni:rtx:background:source:type = "color" and omni:rtx:background:source:color on the USD render product; leaves the default "domeLight" background unchanged when None.
  • PhysX RTX (IsaacRtxRenderer): applies /rtx/background/source/type = 2 (Color mode) and /rtx/background/source/color via the settings manager during camera setup.

• Adds unit tests for the OV RTX USD path (test_ovrtx_usd.py) covering the dome-light default and the solid-color branch.

• Adds changelog fragments for all four touched packages.

• ./isaaclab.sh -p -m pytest source/isaaclab_ov/test/test_ovrtx_usd.py::test_build_render_scope_usd_default_background_is_dome_light passes

• ./isaaclab.sh -p -m pytest source/isaaclab_ov/test/test_ovrtx_usd.py::test_build_render_scope_usd_solid_background_color passes

• Newton renderer renders with correct solid color when background_color=(r, g, b) is set

• OV RTX renderer renders with correct solid color background (no dome light bleed)

• PhysX RTX renderer renders with correct solid color background

• All three backends behave unchanged when background_color=None

Fixes # (OMPE-85828)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (existing functionality will not work without user modification)
• Documentation update

Screenshots

Please attach before and after screenshots of the change if applicable.

IsaacRTX

OVRTX
TODO

Newton

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there

[greptile-apps]

Greptile Summary

This PR adds a background_color: tuple[float, float, float] | None field to CameraCfg and wires it through all three renderer backends (Newton, OV RTX, PhysX RTX) so users can set a solid camera background in a unified, cross-backend way.

• Newton: converts to ARGB uint32 with proper [0, 255] clamping and passes it as SensorTiledCamera.ClearData.clear_color.
• OV RTX: clamps to [0.0, 1.0] and inlines the USD attributes into the generated render scope string; new unit tests cover both the dome-light default and the solid-color branch.
• PhysX RTX: sets the same attributes as per-render-product USD properties on the replicator render product prim, providing per-camera isolation; however, raw float values are forwarded without clamping (unlike the other two backends), and the changelog entry still describes an older carb-settings-manager implementation that no longer matches the code.

Confidence Score: 5/5

Safe to merge; all three backends implement the feature correctly and the default None path is fully backward-compatible.

The change is additive and non-breaking. The Newton and OV RTX implementations include proper clamping and the new tests verify the OV RTX USD output. The PhysX RTX path omits clamping and its changelog entry describes a superseded implementation, but neither issue can cause a crash or data corruption at runtime.

isaac_rtx_renderer.py (missing value clamp) and isaaclab_physx/changelog.d/mataylor-camera-background-color.rst (description does not match implementation).

Important Files Changed

Filename	Overview
source/isaaclab/isaaclab/sensors/camera/camera_cfg.py	Adds `background_color: tuple[float, float, float]
source/isaaclab_newton/isaaclab_newton/renderers/newton_warp_renderer.py	Reads background_color from config, converts to ARGB uint32 with proper clamping, and falls back to the existing 0xFFEEEEEE gray default. Change is clean and consistent.
source/isaaclab_ov/isaaclab_ov/renderers/ovrtx_usd.py	Adds background_color parameter to build_render_scope_usd / build_render_product_as_string; channels are clamped to [0,1] before interpolation. Minor: the else branch comment contradicts what the code does.
source/isaaclab_ov/isaaclab_ov/renderers/ovrtx_renderer.py	Forwards background_color from spec.cfg to build_render_product_as_string via getattr; minimal and correct change.
source/isaaclab_physx/isaaclab_physx/renderers/isaac_rtx_renderer.py	Uses per-render-product USD attributes (not carb settings), which is the right isolation approach. However, raw float values are passed without the [0,1] clamping that the Newton and OV RTX paths apply, and the changelog entry describes a superseded implementation.
source/isaaclab_ov/test/test_ovrtx_usd.py	Two new unit tests cover the dome-light default and the solid-color path; both assertions correctly reflect the current implementation output.
source/isaaclab_physx/changelog.d/mataylor-camera-background-color.rst	Changelog text describes a carb-settings-manager implementation that was superseded by per-render-product USD attributes in the actual code; the description is inaccurate.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["CameraCfg\nbackground_color: tuple | None"] --> B{Which backend?}
    B --> C["Newton\n(NewtonWarpRenderer)"]
    B --> D["OV RTX\n(OVRTXRenderer)"]
    B --> E["PhysX RTX\n(IsaacRtxRenderer)"]

    C --> C1{background_color set?}
    C1 -- Yes --> C2["Clamp to [0,255]\nPack ARGB uint32\nSet ClearData.clear_color"]
    C1 -- No --> C3["Default 0xFFEEEEEE (93% gray)"]

    D --> D1["build_render_scope_usd(background_color=...)"]
    D1 --> D3{background_color set?}
    D3 -- Yes --> D4["Clamp to [0.0,1.0]\nomni:rtx:background:source:type = 'color'\nfloat3 omni:rtx:background:source:color"]
    D3 -- No --> D5["omni:rtx:background:source:type = 'domeLight'"]

    E --> E1{background_color set?}
    E1 -- Yes --> E2["Raw values (no clamp)\nrp_prim.CreateAttribute(type='color')\nrp_prim.CreateAttribute(color=(r,g,b))"]
    E1 -- No --> E3["No USD attr written\n(backend default)"]

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%%{init: {'theme': 'base', 'themeVariables': {"darkMode": true, "background": "#0d1117", "primaryColor": "#21262d", "primaryTextColor": "#e6edf3", "primaryBorderColor": "#8b949e", "lineColor": "#8b949e", "textColor": "#e6edf3", "edgeLabelBackground": "#161b22", "actorBkg": "#21262d", "actorBorder": "#8b949e", "actorTextColor": "#e6edf3", "actorLineColor": "#8b949e", "signalColor": "#8b949e", "signalTextColor": "#e6edf3", "noteBkgColor": "#373320", "noteBorderColor": "#d4a72c", "noteTextColor": "#f0e6c0", "labelBoxBkgColor": "#21262d", "labelBoxBorderColor": "#8b949e", "labelTextColor": "#e6edf3", "loopTextColor": "#e6edf3", "activationBkgColor": "#30363d", "activationBorderColor": "#8b949e"}}}%%
flowchart TD
    A["CameraCfg\nbackground_color: tuple | None"] --> B{Which backend?}
    B --> C["Newton\n(NewtonWarpRenderer)"]
    B --> D["OV RTX\n(OVRTXRenderer)"]
    B --> E["PhysX RTX\n(IsaacRtxRenderer)"]

    C --> C1{background_color set?}
    C1 -- Yes --> C2["Clamp to [0,255]\nPack ARGB uint32\nSet ClearData.clear_color"]
    C1 -- No --> C3["Default 0xFFEEEEEE (93% gray)"]

    D --> D1["build_render_scope_usd(background_color=...)"]
    D1 --> D3{background_color set?}
    D3 -- Yes --> D4["Clamp to [0.0,1.0]\nomni:rtx:background:source:type = 'color'\nfloat3 omni:rtx:background:source:color"]
    D3 -- No --> D5["omni:rtx:background:source:type = 'domeLight'"]

    E --> E1{background_color set?}
    E1 -- Yes --> E2["Raw values (no clamp)\nrp_prim.CreateAttribute(type='color')\nrp_prim.CreateAttribute(color=(r,g,b))"]
    E1 -- No --> E3["No USD attr written\n(backend default)"]

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