---
title: 深度相关
date: 2024-09-09 16:49:08
excerpt: 
tags: 
rating: ⭐
---
# 相关代码
位于common.ush
```c++
#define NearDepthValue (HAS_INVERTED_Z_BUFFER ? 1.0f : 0.0f)  
#define FarDepthValue  (HAS_INVERTED_Z_BUFFER ? 0.0f : 1.0f)
```

可以通过**DeviceZ == FarDepthValue**来判断是否处于最远端。
```c++
	float DeviceZ = DepthReadDisabled ? FarDepthValue : LookupDeviceZ(UvBuffer);
#endif

	if (DeviceZ == FarDepthValue)
	{
		// Get the light disk luminance to draw 
		LuminanceScale = SkyAtmosphere.SkyLuminanceFactor;
#if SOURCE_DISK_ENABLED
		if (SourceDiskEnabled > 0)
		{
			PreExposedL += GetLightDiskLuminance(WorldPos, WorldDir, 0);
		#if SECOND_ATMOSPHERE_LIGHT_ENABLED
			PreExposedL += GetLightDiskLuminance(WorldPos, WorldDir, 1);
		#endif
		}
#endif

#if RENDERSKY_ENABLED==0
		// We should not render the sky and the current pixels are at far depth, so simply early exit.
		// We enable depth bound when supported to not have to even process those pixels.
		OutLuminance = PrepareOutput(float3(0.0f, 0.0f, 0.0f), float3(1.0f, 1.0f, 1.0f));

		//Now the sky pass can ignore the pixel with depth == far but it will need to alpha clip because not all RHI backend support depthbound tests.
		// And the depthtest is already setup to avoid writing all the pixel closer than to the camera than the start distance (very good optimisation).
		// Since this shader does not write to depth or stencil it should still benefit from EArlyZ even with the clip (See AMD depth-in-depth documentation)
		clip(-1.0f);
		return;
#endif
```