Fix Suggenstion for HDRP

[sseiichi]

Version 2.10.0-rc displays pink materials with HDRP and Unity 2022.3.12. Below is a suggested fix, and I hope you will find helpful.

In line 3 of PBRHelpers.cginc:

UnityGLTF/Runtime/Shaders/ShaderGraph/PBRHelpers.cginc

Line 3 in 20b7493

#ifdef SHADERGRAPH_PREVIEW

SHADERGRAPH_PREVIEW must be replaced by another ShaderKeyword used in HDRP, such as SHADERPASS_FORWARD, because it has been removed in the current version of HDRP. Note that SHADERPASS_FORWARD is just an example.
Reference: https://issuetracker.unity3d.com/issues/shadergraph-number-if-shadergraph-preview-in-a-custom-function-node-throws-error

The two functions, SampleSceneColor_float and SampleSceneColor_half, from lines 52 to 72 in PBRHelpers.cginc:

UnityGLTF/Runtime/Shaders/ShaderGraph/PBRHelpers.cginc

Lines 52 to 72 in 20b7493

	void SampleSceneColor_float(float2 uv, float lod, out float3 color)
	{
	#define REQUIRE_OPAQUE_TEXTURE // seems we need to define this ourselves? HDSceneColorNode does that as well
	#if defined(USE_CAMERA_OPAQUE)
	color = SAMPLE_TEXTURE2D_X_LOD(_CameraOpaqueTexture, sampler_CameraOpaqueTexture, UnityStereoTransformScreenSpaceTex(uv), lod).rgb;
	// color = Sample4Tap(uv, lod); // TODO higher quality refraction
	#else
	// For HDRP, from HDSceneColorNode
	#if defined(REQUIRE_OPAQUE_TEXTURE) && defined(_SURFACE_TYPE_TRANSPARENT) && defined(SHADERPASS) && (SHADERPASS != SHADERPASS_LIGHT_TRANSPORT) && (SHADERPASS != SHADERPASS_PATH_TRACING) && (SHADERPASS != SHADERPASS_RAYTRACING_VISIBILITY) && (SHADERPASS != SHADERPASS_RAYTRACING_FORWARD)
	color = SampleCameraColor(uv, lod) * 1.0; // GetInverseCurrentExposureMultiplier()
	#else
	color = float3(0.0, 0.0, 0.0);
	#endif
	#endif
	}
	void SampleSceneColor_half(float2 uv, float lod, out float3 color)
	{
	SampleSceneColor_float(uv, lod, color);
	}

should be nested out of the conditional #if defined(USE_CAMERA_OPAQUE), as this conditional is not executed when HDRP is enabled.

Additionally, for improved convenience, within the Graph Inspector of PBRGraph.shadergraph, HDRP's Surface Type should be Opaque instead of Transparent and Alpha Clipping should be enabled as it is frequently used in many materials.