Using depth and normal textures in unity

1、 Turn on depth and normal textures

By setting Camera Medium depthTextureMode Variable .

camera.depthTextureMode = DepthTextureMode.None;				// Do not generate depth texture 
camera.depthTextureMode = DepthTextureMode.Depth;				// Generate depth texture 
camera.depthTextureMode = DepthTextureMode.DepthNormals;		// Generate depth normal texture 
camera.depthTextureMode = DepthTextureMode.MotionVectors;		// Specifies whether motion vectors should be rendered 

// You can specify to generate multiple textures at the same time by or instructions 
camera.depthTextureMode = DepthTextureMode.Depth | DepthTextureMode.DepthNormals;

2、 Access depth and normal textures

stay shader in , Use variable names _CameraDepthTexture and _CameraDepthNormalsTexture Access the corresponding texture .

sampler2D _CameraDepthTexture;			// Depth texture , The depth value is stored in r passageway , Range [0,1]. adopt MVP Matrix changes z Worthy of 
sampler2D _CameraDepthNormalsTexture;	// Depth normal texture 

Linearization of depth texture

For perspective projection , The stored depth value is nonlinear , To get a linear depth value , Need to transform , It can be done by LinearEyeDepth and Linear01Depth Complete the process

float depth = tex2D(_CameraDepthTexture, uv).r;			// Get the stored depth value 
float depth_view = LinearEyeDepth(depth);				// Get the depth value in the perspective space , The range is between the near plane and the far plane ,[z_near, z_far]
float depth_01 = Linear01Depth(depth);					// obtain [0,1] Depth value of linear distribution in the range , 0 In camera position ,1 In the far plane 

Use of depth normal texture

The depth normal texture is 32bit code ( Every channel 8bit), Normal information is stored in R and G passageway , Depth information is stored in B and A passageway . The depth value is 16bit The data of , Stored separately in two 8bit In the channel .
therefore , To use a depth normal texture , After sampling, it needs to be decoded before it can be used . You can use UnityCG.cginc Medium DecodeDepthNormal decode .

inline void DecodeDepthNormal( float4 enc, out float depth, out float3 normal )
{
    
    depth = DecodeFloatRG (enc.zw);
    normal = DecodeViewNormalStereo (enc);
}

float4 samplerValue = tex2D(_CameraDepthNormalsTexture, i.uv);
float depth;		//depth The end result is [0,1] Linear distribution of ranges 
float3 normal;		//normal Is the normal direction in screen space 
DecodeDepthNormal(samplerValue, depth, normal);	

3、 Display the depth value and normal value

Depth texture display ：

float4 samplerValue = tex2D(_CameraDepthNormalsTexture, i.uv);
float depth;		//depth The end result is [0,1] Linear distribution of ranges 
float3 normal;		//normal Is the normal direction in screen space 
DecodeDepthNormal(samplerValue, depth, normal);	

return fixed4(depth, depth, depth,1);

Normal texture display ：

float4 samplerValue = tex2D(_CameraDepthNormalsTexture, i.uv);
float depth;		//depth The end result is [0,1] Linear distribution of ranges 
float3 normal;		//normal Is the normal direction in screen space 
DecodeDepthNormal(samplerValue, depth, normal);	

return fixed4(normal*0.5+0.5,1);

4、 Reference material

[1] Feng Lele 《Unity Shader Introduction to topic 》 page 269-272
[2] Unity manual https://docs.unity3d.com/2020.2/Documentation/Manual/SL-CameraDepthTexture.html