Mercurial > cortex
comparison thesis/cortex.org @ 476:5a15611fbb9f
make latex happy.
author | Robert McIntyre <rlm@mit.edu> |
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date | Fri, 28 Mar 2014 22:09:03 -0400 |
parents | 3ec428e096e5 |
children | ba54df21fc7c |
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475:3ec428e096e5 | 476:5a15611fbb9f |
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1739 Triangles are [[http://mathworld.wolfram.com/AffineTransformation.html ][affine]], which means any triangle can be transformed | 1739 Triangles are [[http://mathworld.wolfram.com/AffineTransformation.html ][affine]], which means any triangle can be transformed |
1740 into any other by a combination of translation, scaling, and | 1740 into any other by a combination of translation, scaling, and |
1741 rotation. The affine transformation from one triangle to another | 1741 rotation. The affine transformation from one triangle to another |
1742 is readily computable if the triangle is expressed in terms of a | 1742 is readily computable if the triangle is expressed in terms of a |
1743 $4x4$ matrix. | 1743 $4x4$ matrix. |
1744 | 1744 |
1745 #+BEGIN_LaTeX | |
1746 $$ | |
1745 \begin{bmatrix} | 1747 \begin{bmatrix} |
1746 x_1 & x_2 & x_3 & n_x \\ | 1748 x_1 & x_2 & x_3 & n_x \\ |
1747 y_1 & y_2 & y_3 & n_y \\ | 1749 y_1 & y_2 & y_3 & n_y \\ |
1748 z_1 & z_2 & z_3 & n_z \\ | 1750 z_1 & z_2 & z_3 & n_z \\ |
1749 1 & 1 & 1 & 1 | 1751 1 & 1 & 1 & 1 |
1750 \end{bmatrix} | 1752 \end{bmatrix} |
1753 $$ | |
1754 #+END_LaTeX | |
1751 | 1755 |
1752 Here, the first three columns of the matrix are the vertices of | 1756 Here, the first three columns of the matrix are the vertices of |
1753 the triangle. The last column is the right-handed unit normal of | 1757 the triangle. The last column is the right-handed unit normal of |
1754 the triangle. | 1758 the triangle. |
1755 | 1759 |
1756 With two triangles $T_{1}$ and $T_{2}$ each expressed as a matrix | 1760 With two triangles $T_{1}$ and $T_{2}$ each expressed as a |
1757 like above, the affine transform from $T_{1}$ to $T_{2}$ is | 1761 matrix like above, the affine transform from $T_{1}$ to $T_{2}$ |
1758 | 1762 is $T_{2}T_{1}^{-1}$. |
1759 $T_{2}T_{1}^{-1}$ | |
1760 | 1763 |
1761 The clojure code below recapitulates the formulas above, using | 1764 The clojure code below recapitulates the formulas above, using |
1762 jMonkeyEngine's =Matrix4f= objects, which can describe any affine | 1765 jMonkeyEngine's =Matrix4f= objects, which can describe any affine |
1763 transformation. | 1766 transformation. |
1764 | 1767 |