Delta-like symbol in LaTeX

Question

I'd like to write a majuscule delta-like symbol in LaTeX but I can't find it's syntax anywhere. You can see the symbol on equation (12) of the following paper:

"Two-Frame Motion Estimation Based on Polynomial Expansion".

Answer 1

Note that the document uses Springer's LNCS style. In this style, all Greek letters are in italics, and vectors are denoted by boldface.

Most likely the bold italic Delta is produced in this particular case by something similar to this:

\documentclass{llncs}
\begin{document}
$\vec{\Delta}$
\end{document}

The result is:

Note that if you used the article class, the same code would produce a normal Delta with an arrow:

Answer 2

If one really wants a bold italic Delta, the way to go is

\usepackage{bm}
\newcommand{\bfitDelta}{\bm{\mathit{\Delta}}}

Of course, one could write every time \bm{\mathit{\Delta}}.

Answer 3

That is just $\Delta$ which is different from $\delta$. LateX symbols are case-sensitive. See any of the LaTeX cheat sheets as e.g. this one a U Colorado.

Answer 4

Use http://detexify.kirelabs.org/classify.html

From your description, it seems you mean \triangle, \Delta or \vartriangle.