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2010年4月3日 (土) 12:25にwiki>Terrywallworkによる

2010-04-03T12:25:49Z

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As part of work on the modifier system I need to rework how curves/surfaces were
handled. The code for Curves is pretty ancient and nasty, probably one of the
worst parts of Blender. I thought it would be worthwhile to jot down some notes
for future reference as I figured stuff out.

<source lang="cpp">curve_to_displist(ListBase *nubase, ListBase *dispbase)</source>

This one is pretty simple, just tesselates each struct Nurb in the given list
into a displist (either a DL_POLY or DL_SEGM). DL_POLY is a line loop,
DL_SEGM is a line strip.

<source lang="cpp">makeBevelList(Object *ob)</source>

This function tesselates the curve itself into a list of BevList objects, storing
them in cu->bev. Each item in the list is actually a BevList object followed (in memory)
by an array of BevPoint objects. Hence the code "bevp = (BevPoint) (&bl + 1)". The array
has length "BevList.nr". BevPoints have a position ("x,y,z"), a flag ("f1") for if the
BevPoint should be split (every point in a poly curve, or points in a bezier curve with
sharp corners), and extra information to calculate bevel orientation (for 2d curves this
is two angles ("cosa", "sina"), for 3d curves it is a rotation matrix ("mat")). There is an
"alfa" field which copies the "alfa" field from the curve BPoint/BezTriple's but I don't know
what it is supposed to be (I think it is time parametrization of curve). Generally (except
for curves with 1 point) there is a BevList entry for each struct Nurb element in the Curve.

The routine also does things like removing double points and some other things relating
to holes that I haven't bothered to understand.

<source lang="cpp">makebevelcurve(Object *ob, ListBase *dispbase)</source>

This function builds a list of DispList objects that represent the bevel outline.
This outline can either be just a line (ext1>0, ext2==0, bevelobj==0), or a simple
bevel (ext1=0,ext2=0,bevelobj==0) which is a line with half circle at each end,
or a complex curve (bevelobj=0) which can be anything. For the bevelobj case the
displist is copied of the bevelobj itself (which was made by curve_to_displist). The
input curve is expected to live in the XY plane.

The function shuffles the coordinates of the returned displist so that the X coordinate
is 0, and the curve XY become YZ in the displist respectively.

<source lang="cpp">curve_to_filledpoly(Curve *cu, ListBase *nurb, ListBase *dispbase)</source>

This function handles creating a filled polygon for either a single simple filled
curve or the filled top/bottom of a bevelled curve.

-- [[DeveloperWiki/DanielDunbar|DanielDunbar]] - 13 Aug 2005

[[Category:Notes]]
[[Category:Script]]

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2010年4月3日 (土) 12:25にwiki>Terrywallworkによる

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