Study on Gradient
Going on with studying the math involved in fluid simulation, I created this patch that visualizes the gradient of a 2D scalar field. 

The gradient of a scalar field, such as the results of a 2D function on the x,y plane, gives us a vector field, with every vector pointing in the direction in which the function is changing the most. 

When the line is blue the "steepness" is less (function is not changing much), when is red is greater (function changing faster).

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