Unity - Scripting API: Graphics.Blit

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Declaration

public static void Blit(Texture source, Material mat, int pass = -1);

Declaration

public static void Blit(Texture source, Material mat, int pass, int destDepthSlice);

Declaration

public static void Blit(Texture source, RenderTexture dest, int sourceDepthSlice, int destDepthSlice);

Parameters

Parameter	Description
source	The source texture.
dest	The destination RenderTexture or GraphicsTexture.
mat	The material to use. If you don't provide `mat`, Unity uses a default material.
pass	If the value is `-1`, Unity draws all the passes in `mat`. Otherwise, Unity draws only the pass you set `pass` to. The default value is `-1`.
scale	The scale to apply to the source texture. Unity uses this scale value to multiply the UVs it uses to sample the source texture.
offset	The offset to apply to the source texture. Unity adds this offset value to the UVs before sampling the source texture. The offset is independent from the scale as Unity adds the offset only after it applies the scale.
sourceDepthSlice	The element in the source texture to copy from, for example the texture in a texture array. You can't use `sourceDepthSlice` to specify a face in a Cubemap.
destDepthSlice	The element in the destination texture to copy from, for example the texture in a texture array. You can't use `destDepthSlice` to specify a face in a Cubemap.

Description

Uses a shader to copy the pixel data from a texture into a render target.

This method copies pixel data from a texture on the GPU to a render texture or graphics texture on the GPU. This is one of the fastest ways to copy a texture.

When you use Graphics.Blit, Unity does the following:

Sets the active render target to the dest texture. (See RenderTexture.active and GraphicsTexture.active.)
Passes source to the mat material as the _MainTex property.
Uses the material's shader to draw a full-screen surface from the source texture to the dest texture.

Set dest to null. Unity now uses Camera.main.targetTexture as the destination texture.
Set the Camera.targetTexture property of Camera.main to null.

Copies aTexture to rTex and displays it in all cameras.

Execute a Blit from the source texture to the destination using a custom blit shader assigned to the fishEyeMaterial field.

          Shader "Custom/FishEyeShader"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _Distortion ("Distortion Strength", Range(0, 1)) = 0.5
    }
    SubShader
    {
        Pass
        {
            ZTest Always
            Cull Off
            ZWrite Off            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            sampler2D _MainTex;
            float _Distortion;
            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };
            struct v2f
            {
                float4 pos : SV_POSITION;
                float2 uv : TEXCOORD0;
            };
            v2f vert(appdata v)
            {
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }
            float4 frag(v2f i) : COLOR
            {
                float2 uv = i.uv;
                float2 center = float2(0.5, 0.5); // Center of the texture
                // Fisheye distortion
                float2 diff = uv - center;
                float dist = length(diff);
                diff *= pow(_Distortion, dist);
                uv = center + diff; // Apply distortion
                return tex2D(_MainTex, uv);
            }
            ENDCG
        }
    }
}

Shader code used for the fish eye effect.