# Changes between Version 10 and Version 11 of MousePicking

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Timestamp:
05/18/06 14:53:28 (13 years ago)
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• ## MousePicking

v10 v11
120120\end{eqnarray*}
121121}}}
122
123So we need to do the inverse of this process by rearranging to solve for '''n''':
124
125{{{
126#!latex-math-hook
127
128\begin{equation*}
129\label{eqn:vp to ndc}
130{\boldsymbol n} = \begin{pmatrix}
131\frac{ 2{\boldsymbol v}_x }w - 1\\
132\frac{ 2{\boldsymbol v}_y }{h}\\
1332{\boldsymbol v}_z - 1\\
1341
135\end{pmatrix}
136\end{equation*}
137}}}
138
139Okay, not so bad. The only real question is the {{{z}}} component of '''v'''.  We can either calculate that value by reading it back from the framebuffer, or ignore it by substituting 0, in which case we'll be computing a ray passing through '''v''' that we'll then have to intersect with world geometry to find the corresponding point in 3-space.
140
141From here we need to go to clip coordinates, which, if you recall, are the homogeneous versions of the NDC coordinates (i.e. ''w'' != 1.0). Since ''w'' is already 1.0 and the transformation back to clip
142coordinates is a scale by ''w'', this step can be skipped and we can assume that our NDC coordinates are the same as our clip coordinates.
143
144=== Clipping Space to View Space ===