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# How to use Unity to achieve sci-fi projection effects?

How to use Unity to achieve sci-fi projection effects? I am learning Shader and record the holographic projection effect I just played.

Look at the original model first:

## Unity to achieve sci-fi projection effects

When it comes to holographic projection, the first thing that comes to mind is a scan line, which scans layer by layer along the projection direction on the model.

The principle is also relatively simple. Prepare a scan sample map, sample according to the model’s x coordinate in the fragment shader and add the time variable.

```// Scan line flow animation
fixed scroll = _Speed * _Time;
fixed4 col = tex2D(_MainTex,i.uv);
fixed scrollProject =abs(i.objectPos.x+scroll - round(i.objectPos.x+scroll));
fixed4 cybercol = tex2D(_CyberTex, scrollProject);
fixed alpha = 1;
if(cybercol.r + cybercol.g + cybercol.b < 1){
alpha = 0;
col = max(cybercol,col);
} ```

A very rough scan line is achieved.

## Edge light effect

Then calculate the point product of the angle of view and the normal, plus the edge light effect.

```//Edge light
fixed edge = pow(i.VdotN, 1) / _Range;
edge = edge> _OutlineThred? 1: edge;
edge = 1-edge;
//The part less than thred is regarded as the edge
fixed4 edgeCol = pow(edge, 0.1) * fixed4(_EdgeColor.rgb + fixed3(0.3,0.3,0.5) * (sin(_Time.y * 3)+1)*0.5,edge);
//Edge color processing
col = col*(1-edgeCol.a)+edgeCol*edgeCol.a;```

Finally, two passes are added (one of which is practical to expand outside the line) to make the afterimage effect, and the algorithm of each pass is basically the same as the previous one.

The complete code is as follows:

```Shader "Cyber/cyberProjection"
{
Properties
{
_CyberTex ("Cyber ​​Texture", 2D) = "white" {}
_CyberTexBack ("Cyber ​​Texture Back", 2D) = "white" {}
_MainTex ("Main Texture", 2D) = "white" {}

[HDR]_EdgeColor("Edge Color", Color) = (1,1,1,1)
[HDR]_OutsideColor("Outside Color", Color) = (1,1,1,1)

_Speed("Speed", Range(-5,5)) = 1
_OutlineThred("OutlineThred", Range(0,1)) = 0.5
_Range("Range", Range(0,2)) = 1
_Size("Size", Range(0,1)) = 0.5
}
{
Tags {"RenderType"="Transparent" "Queue" = "Transparent" "IgnoreProjector" = "True" "ForceNoShadowCasting" = "True"}
LOD 100
Blend SrcAlpha OneMinusSrcAlpha

Pass
{
// Cull Off

CGPROGRAM
#pragma vertex vert
#pragma fragment frag
// make fog work
#pragma multi_compile_fog

#include "UnityCG.cginc"

struct appdata
{
float4 vertex: POSITION;
float2 uv: TEXCOORD0;
fixed3 normal: NORMAL;

};

struct v2f
{
float2 uv: TEXCOORD0;
float4 vertex: SV_POSITION;
float4 objectPos: TEXCOORD1;
float4 VdotN: TEXCOORD2;
UNITY_FOG_COORDS(3)
};

sampler2D _CyberTex;
float4 _CyberTex_ST;
float4 _CyberTex_TexelSize;

sampler2D _MainTex;
float4 _MainTex_ST;

// fixed4 _MainColor;
fixed4 _EdgeColor;

fixed _Speed;
fixed _Offset;
float _Range;
float _OutlineThred;

v2f vert (appdata v)
{
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
o.uv = TRANSFORM_TEX(v.uv, _CyberTex);
o.objectPos = v.vertex;
float3 viewDir = normalize(
mul(unity_WorldToObject,
float4(_WorldSpaceCameraPos.xyz, 1)).xyz-v.vertex);
o.VdotN = dot(normalize(viewDir),v.normal);

UNITY_TRANSFER_FOG(o,o.vertex);

return o;
}

fixed4 frag (v2f i): SV_Target
{
// Flow animation
fixed scroll = _Speed ​​* _Time;
fixed4 col = tex2D(_MainTex,i.uv);
fixed scrollProject =abs(i.objectPos.x+scroll-round(i.objectPos.x+scroll));

fixed4 cybercol = tex2D(_CyberTex, scrollProject);

fixed alpha = 1;
alpha -= i.objectPos.x;
if(cybercol.r + cybercol.g + cybercol.b <1){
alpha = 0;
col = max(cybercol,col);
}

//Edge light
fixed edge = pow(i.VdotN, 1) / _Range;
edge = edge> _OutlineThred? 1: edge;
edge = 1-edge;
//The part less than thred is regarded as the edge
fixed4 edgeCol = pow(edge, 0.1) * fixed4(_EdgeColor.rgb + fixed3(0.3,0.3,0.5) * (sin(_Time.y * 3)+1)*0.5,edge);
//Edge color processing
col = col*(1-edgeCol.a)+edgeCol*edgeCol.a;

UNITY_APPLY_FOG(i.fogCoord, col);

return fixed4(col.rgb,alpha);
}
ENDCG
}
Pass
{
// Cull Off

CGPROGRAM
#pragma vertex vert
#pragma fragment frag
// make fog work
#pragma multi_compile_fog

#include "UnityCG.cginc"

struct appdata
{
float4 vertex: POSITION;
float2 uv: TEXCOORD0;
};

struct v2f
{
float2 uv: TEXCOORD0;
float4 vertex: SV_POSITION;
float4 objectPos: TEXCOORD1;
float4 VdotN: TEXCOORD2;
UNITY_FOG_COORDS(3)
};

sampler2D _CyberTexBack;
float4 _CyberTexBack_ST;
float4 _CyberTexBack_TexelSize;

sampler2D _MainTex;
float4 _MainTex_ST;

float4 _OutsideColor;

// fixed4 _MainColor;
fixed _Speed;
fixed _Offset;
fixed _Size;

v2f vert (appdata v)
{
v2f o;
v.vertex.x -= _Size;
v.vertex.y -= _Size;
v.vertex.z -= _Size;
o.vertex = UnityObjectToClipPos(v.vertex);
o.uv = TRANSFORM_TEX(v.uv, _CyberTexBack);
o.objectPos = v.vertex;

UNITY_TRANSFER_FOG(o,o.vertex);
return o;
}

fixed4 frag (v2f i): SV_Target
{
fixed scroll = _Speed ​​* _Time / 2;
fixed4 col = tex2D(_MainTex,i.uv);
fixed scrollProject =abs(i.objectPos.x+scroll-round(i.objectPos.x+scroll));

fixed4 cybercol = tex2D(_CyberTexBack, scrollProject);

fixed alpha = 1;
if(cybercol.r + cybercol.g + cybercol.b <1){
alpha = 0;
col = min(cybercol,col);
}

col *= _OutsideColor;

UNITY_APPLY_FOG(i.fogCoord, col);

return fixed4(col.rgb,alpha*0.5);
}
ENDCG
}
Pass
{
// Cull Off

CGPROGRAM
#pragma vertex vert
#pragma fragment frag
// make fog work
#pragma multi_compile_fog

#include "UnityCG.cginc"

struct appdata
{
float4 vertex: POSITION;
float2 uv: TEXCOORD0;
};

struct v2f
{
float2 uv: TEXCOORD0;
float4 vertex: SV_POSITION;
float4 objectPos: TEXCOORD1;
float4 VdotN: TEXCOORD2;
UNITY_FOG_COORDS(3)
};

sampler2D _CyberTexBack;
float4 _CyberTexBack_ST;
float4 _CyberTexBack_TexelSize;
float4 _OutsideColor;

sampler2D _MainTex;
float4 _MainTex_ST;

// fixed4 _MainColor;
fixed _Speed;
fixed _Offset;
fixed _Size;

v2f vert (appdata v)
{
v2f o;
v.vertex.x += _Size;
v.vertex.y += _Size;
v.vertex.z += _Size;
o.vertex = UnityObjectToClipPos(v.vertex);
o.uv = TRANSFORM_TEX(v.uv, _CyberTexBack);
o.objectPos = v.vertex;

UNITY_TRANSFER_FOG(o,o.vertex);
return o;
}

fixed4 frag (v2f i): SV_Target
{
fixed scroll = _Speed ​​* _Time * 2;
fixed4 col = tex2D(_MainTex,i.uv);
fixed scrollProject =abs(i.objectPos.x+scroll-round(i.objectPos.x+scroll));

fixed4 cybercol = tex2D(_CyberTexBack, scrollProject);

fixed alpha = 1;
if(cybercol.r + cybercol.g + cybercol.b <1){
alpha = 0;
col = min(cybercol,col);
}
col *= _OutsideColor;

UNITY_APPLY_FOG(i.fogCoord, col);

return fixed4(col.rgb,alpha*0.5);
}
ENDCG
}
}
}
```