Shader-边缘检测

原创已于 2022-10-08 20:54:28 修改 · 358 阅读

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于 2022-10-07 16:05:51 首次发布

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这篇博客介绍了如何在Unity中实现Sobel Edge Detection算法，通过Shader检测图像边缘。内容包括Shader的编写，涉及到纹理采样、像素操作等技术。

Shader "CX/Edge Detection" /* The edge detection algorithm that is implemented in this shader is named "Sobel Edge Detection" */
{
Properties
{
_Color ("Color", Color) = (1,1,1,1)
}
SubShader
{
Tags { "Queue"="Transparent" }
Cull Back

GrabPass { }

Pass
{
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"

struct appdata
{
float4 vertex : POSITION;
float3 normal : NORMAL;
};

struct v2f
{
float4 position : POSITION;
float4 screenPos : TEXCOORD0;
};

fixed4 _Color;
sampler2D _GrabTexture : register(s0);

v2f vert(appdata input)
{
v2f output;

output.position = UnityObjectToClipPos(input.vertex);
output.screenPos = output.position;

return output;
}

half4 pixel;
half2 uv;
fixed onePixelW, onePixelH;
half4 frag(v2f input) : SV_Target
{
uv = input.screenPos.xy / input.screenPos.w;
uv.x = (uv.x + 1) * .5;
uv.y = 1.0 - (uv.y + 1) * .5;

onePixelW = 1.0 / _ScreenParams.x;
onePixelH = 1.0 / _ScreenParams.y;

pixel = 0;
pixel = abs(
tex2D(_GrabTexture, half2(uv.x - onePixelW, uv.y)) -
tex2D(_GrabTexture, half2(uv.x + onePixelW, uv.y)) +
tex2D(_GrabTexture, half2(uv.x, uv.y + onePixelH)) -
tex2D(_GrabTexture, half2(uv.x, uv.y - onePixelH))
);

return pixel * _Color;
}
ENDCG
}
}
}