ue对 scene depth的封装

SceneTexturesCommon.ush

float LookupDeviceZ( float2 ScreenUV )
{
//mg_hack
//return 1;
#if	SCENE_TEXTURES_DISABLED
	return FarDepthValue;
#elif (POST_PROCESS_MATERIAL || POST_PROCESS_MATERIAL_MOBILE) && !POST_PROCESS_AR_PASSTHROUGH
	#if MOBILE_DEFERRED_SHADING
		return Texture2DSample(MobileSceneTextures.SceneDepthAuxTexture, MobileSceneTextures.SceneDepthAuxTextureSampler, ScreenUV).r;
	#else
		// SceneDepth texture is not accessible during post-processing as we discard it at the end of mobile BasePass
		// instead fetch DeviceZ from SceneColor.A
		return Texture2DSample(MobileSceneTextures.SceneColorTexture, MobileSceneTextures.SceneColorTextureSampler, ScreenUV).a;
	#endif
#elif COMPILER_GLSL_ES3_1 && PIXELSHADER
	#if !OUTPUT_MOBILE_HDR
		// Try framebuffer_fetch_depth_stencil to get the depth directly if the extension is available.
		// We cannot fall back to fetching the alpha channel when MobileHDR=false because the alpha channel is only 8-bit.
		return DepthbufferFetchES2();
	#else
		return FramebufferFetchES2().w;
	#endif
#elif VULKAN_SUBPASS_DEPTHFETCH && PIXELSHADER
	// Special intrinsic to read from the current depth buffer
	return VulkanSubpassDepthFetch();
#elif (METAL_PROFILE && !MAC) && PIXELSHADER
	return DepthbufferFetchES2();
#else
	// native Depth buffer lookup
	return Texture2DSampleLevel(MobileSceneTextures.SceneDepthTexture, MobileSceneTextures.SceneDepthTextureSampler, ScreenUV, 0).r;
#endif
}

/** Returns clip space W, which is world space distance along the View Z axis. Note if you need DeviceZ LookupDeviceZ() is the faster option */
float CalcSceneDepth(float2 ScreenUV)
{
#if SCENE_TEXTURES_DISABLED
	return SCENE_TEXTURES_DISABLED_SCENE_DEPTH_VALUE;
#else
	return ConvertFromDeviceZ(LookupDeviceZ(ScreenUV));
#endif
}

CalcSceneDepth

材质编辑器那边加的节点里面的代码是这个

CalcSceneDepth