Reproduction steps:
1. Open the attached “IN-54298 Terrain Altitude Heatmap Bug 2.zip“ project
2. Open the “OutdoorsScene”
3. Move the Scene view Camera to a point from which the “Terrain” GameObject is clearly visible
4. Go to Window > Terrain > Terrain Toolbox
5. Open the “Terrain Visualization” tab in the Terrain Toolbox window
6. In the “Visualization Modes” drop-down menu, select the “Altitude Heatmap”

Expected result: The Altitude Heatmap is drawn on the surface of the “Terrain” with a gradient of colours from blue to red
Actual result: The Altitude Heatmap is not drawn and an error is logged in the Console

Reproducible with: 5.0.3 (2022.2.0a16, 2022.3.10f1), 5.1.0 (2023.1.15f1, 2023.2.0b11, 2023.3.0a7)
Not reproducible with: 4.0.5 (2021.3.30f1), 5.0.3 (2022.2.0a15)

Reproduced on: Windows 11 Pro (22H2)
Not reproduced on: No other environment tested

Notes:
- Not reproducible with “3D” and “3D (URP)” Project Templates
- When “Lit Shader Mode” is set to “Forward only”, another error is also logged in the Console (see internal notes) and a pink texture gets applied to the “Terrain”
- Reproducible in a new project
- Could not test in Player (Altitude Heatmap is not displayed)
- Reproducible with all Graphics APIs supported with HDRP: D3D11, D3D12, Vulkan
- When the actual result is reproduced, the “Terrain” itself is no longer drawn as well (skybox trails are drawn instead of the “Terrain” when moving the Scene view Camera)
- The regression is in the Editor versions, not the Package versions

Full error message:
Shader error in 'Hidden/HDRP_TerrainVisualization': 'GetSurfaceAndBuiltinData': output parameter 'surfaceData' not completely initialized at Ghost/Library/PackageCache/com.unity.terrain-tools@5.0.3/Shaders/Visualization/HDRP/HDRP_TerrainVisualizationData.hlsl(148) (on d3d11)

Compiling Subshader: 0, Pass: GBuffer, Fragment program with DECALS_4RT INSTANCING_ON LIGHT_LAYERS LOCAL_SPACE _HEATMAP
Platform defines: SHADER_API_DESKTOP UNITY_ENABLE_DETAIL_NORMALMAP UNITY_ENABLE_REFLECTION_BUFFERS UNITY_LIGHTMAP_FULL_HDR UNITY_LIGHT_PROBE_PROXY_VOLUME UNITY_PBS_USE_BRDF1 UNITY_SPECCUBE_BLENDING UNITY_SPECCUBE_BOX_PROJECTION UNITY_USE_DITHER_MASK_FOR_ALPHABLENDED_SHADOWS
Disabled keywords: DEBUG_DISPLAY DECALS_3RT DECALS_OFF DIRLIGHTMAP_COMBINED DYNAMICLIGHTMAP_ON LIGHTMAP_ON SHADER_API_GLES30 SHADOWS_SHADOWMASK UNITY_ASTC_NORMALMAP_ENCODING UNITY_COLORSPACE_GAMMA UNITY_FRAMEBUFFER_FETCH_AVAILABLE UNITY_HALF_PRECISION_FRAGMENT_SHADER_REGISTERS UNITY_HARDWARE_TIER1 UNITY_HARDWARE_TIER2 UNITY_HARDWARE_TIER3 UNITY_LIGHTMAP_DLDR_ENCODING UNITY_LIGHTMAP_RGBM_ENCODING UNITY_METAL_SHADOWS_USE_POINT_FILTERING UNITY_NO_DXT5nm UNITY_NO_FULL_STANDARD_SHADER UNITY_NO_SCREENSPACE_SHADOWS UNITY_PBS_USE_BRDF2 UNITY_PBS_USE_BRDF3 UNITY_PRETRANSFORM_TO_DISPLAY_ORIENTATION UNITY_UNIFIED_SHADER_PRECISION_MODEL UNITY_VIRTUAL_TEXTURING WORLD_SPACE _DISABLE_DECALS _MASKMAP _NORMALMAP _SPLATMAP_PREVIEW _TERRAIN_8_LAYERS _TERRAIN_BLEND_HEIGHT _TERRAIN_INSTANCED_PERPIXEL_NORMAL