Unity 2018 Shaders and Effects Cookbook

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Where swizzling really shows its full potential is when it's applied to packed matrices. Cg allows types such as float4x4, which represents a matrix of floats with four rows and four columns. You can access a single element of the matrix using the _mRC notation, where R is the row and C is the column:

float4x4 matrix; 
// ... 
float first = matrix._m00; 
float last = matrix._m33; 

The _mRC notation can also be chained:

float4 diagonal = matrix._m00_m11_m22_m33; 

An entire row can be selected using squared brackets:

float4 firstRow = matrix[0]; 
// Equivalent to 
float4 firstRow = matrix._m00_m01_m02_m03;