[Feature] WebGPU-WebGL feature parity

[daker]

Motivation

WebGPU is the path to better scalability, better GPU resource management, and more future-proof rendering performance for the kinds of large datasets.

Browser support :

• Chrome, Edge, and other Chromium-based browsers:

  • WebGPU is available on Windows (with Direct3D 12), macOS, and ChromeOS starting with Chrome and Edge version 113.
  • Support for Android was added in Chrome version 121 for devices running at least Android 12, and with Qualcomm/ARM GPUs.
  • Support for Linux and expanded support for existing platforms is in progress.

• Firefox:

  • WebGPU is available on Windows as of Firefox 141.
  • WebGPU is available in macOS Tahoe 26 on ARM64 machines, as of Firefox 145.
  • Support for Linux, Android, and Intel-based Macs is in progress.

• Safari:

  • WebGPU is available in macOS Tahoe 26, iOS 26, iPadOS 26, and visionOS 26.

Detailed Description

Texture:

• Subimage texture uploads Texture.writeSubImageData feat(WebGPU): implement subimage texture upload #3477

Background:

• Support a vtkBackground(background clear, gradient, texture, skybox) in WebGPU

SkyBox:

• Support a vtkSkyBox in WebGPU

ImageCPRMapper:

• feat(ImageCPRMapper): add ImageCPRMapper in WebGPU #3471

PolydataMapper/CellArrayMapper:

• Backface material support (feat(WebGPU): add polydata backface material and local culling #3475)
• Coincident topology / polygon offset handling (feat(WebGPU): add coincident topology offsets to CellArrayMapper #3479)
• Clipping planes (feat(WebGPU): add clipping plane support for polydata, volume and image #3464)
• Depth only / z-buffer pass support
• Front/back face culling controls (feat(WebGPU): add polydata backface material and local culling #3475)
• Suport scalars at cells (i.e. support texture maps)

ImageMapper:

• Opacity transfer-function support via piecewise-function LUTs (feat(WebGPU): add ImageMapper #3482)
• Independent-components mode with per-component weights/mixing (feat(WebGPU): add ImageMapper #3482)
• Dependent multicomponent(LA/RGB/RGBA) image modes (feat(WebGPU): add ImageMapper #3482)
• Label-outline rendering for labelmaps (feat(WebGPU): add ImageMapper #3482)
• Clipping planes (feat(WebGPU): add clipping plane support for polydata, volume and image #3464)
• Z-buffer/depth pass (feat(WebGPU): add ImageMapper #3482)
• Coincident topology / polygon offset (feat(WebGPU): add ImageMapper #3482)
• useLookupTableScalarRange (feat(WebGPU): add ImageMapper #3482)

ImageResliceMapper:

• Support a vtkImageResliceMapper(extend vtkWebGPUImageMapper) in WebGPU

VolumeMapper/VolumePassFSQ:

• Volumetric lighting
• True multi component volume sampling
• Independent component mixing with component weights / ColorMixPreset behaviors
• RADON_TRANSFORM_BLEND
• LABELMAP_EDGE_PROJECTION_BLEND
• Labelmap outline thickness rendering
• Clipping planes (feat(WebGPU): add clipping plane support for polydata, volume and image #3464)
• Intermixed rendering against opaque geometry via z-buffer input
• Volumetric scattering / global illumination controls
• Local ambient occlusion (LAO)
• ForceNearestInterpolation per component
• computeNormalFromOpacity support
• Volume shadow sampling distance factor support

CutterMapper:

• feat(CutterMapper): add vtkCutterMapper #3466

HardwareSelector:

• missing attach

[finetjul]

I added the lack of support for scalars at cells for the polydata mapper.
vtkMapper enforces texture mapping but WebGPU mapper does not support texture mapping.