dFdx, dFdy — return the partial derivative of an argument with respect to x or y
genType dFdx( | genType p); |
genType dFdy( | genType p); |
Available only in the fragment shader, dFdx and dFdy
return the partial derivative of expression p in x and y, respectively. Deviatives are calculated
using local differencing. Expressions that imply higher order derivatives such as dFdx(dFdx(n)) have undefined
results, as do mixed-order derivatives such as dFdx(dFdy(n)).
It is assumed that the expression p is continuous and therefore, expressions evaluated
via non-uniform control flow may be undefined.
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