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User:Hg200: Difference between revisions
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== OpenGL coordinate systems == | == OpenGL coordinate systems == | ||
[[File:Octave_coordinate_systems.png|center| | In the Octave plotting backend, we find various OpenGL transformations. Some of the classic OpenGL transformation steps, as well as coordinate systems, are shown in the following picture: | ||
[[File:Octave_coordinate_systems.png|center|350px]] | |||
== The role of "x_gl_mat1" == | == The role of "x_gl_mat1" == | ||
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bb(0), bb(1): Position of the "viewport" | bb(0), bb(1): Position of the "viewport" | ||
bb(2), bb(3): Width and height of the "viewport" | bb(2), bb(3): Width and height of the "viewport" | ||
Hint: If you debug in "update_camera ()", you can print "bb": | |||
(gdb) print *bb.rep.data@bb.rep.len | |||
Compare the result with the output in the Octave prompt: | |||
hax = axes (); | |||
get (hax, "position"); | |||
In the following simplified code section, the field of view (FOV) is determined such that the image is fitted into the bounding box of the window: | In the following simplified code section, the field of view (FOV) is determined such that the image is fitted into the bounding box of the window: | ||
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</syntaxhighlight>}} | </syntaxhighlight>}} | ||
x_viewport is a 2D transformation used to place the "normalized" plot box in the center of the bounding box: | "x_viewport" is a 2D transformation used to place the "normalized" plot box in the center of the bounding box: | ||
{{Code|Section of axes::properties::update_camera ()"|<syntaxhighlight lang="C" style="font-size:13px"> | {{Code|Section of axes::properties::update_camera ()"|<syntaxhighlight lang="C" style="font-size:13px"> | ||