平面挖洞算法

引用 16 楼 rootxue 的回复:

caozl和dizuo理解对了,其它的唉~~~

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不错,支持
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圈住一个封闭图形后，直接用指定的像素值取代里面的所有像素值
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可根据定点确定图形图形圈住一个封闭图形后，直接用指定的像素值取代里面的所有像素值 ，
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是啊，挖去和补上其实是同一个概念。可以用填充来实现你的要求。
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Polygon
The Polygon function draws a polygon consisting of two or more vertices connected by straight lines. The polygon is outlined by using the current pen and filled by using the current brush and polygon fill mode. 

BOOL Polygon(
  HDC hdc, // handle to device context
  CONST POINT *lpPoints, // pointer to polygon's vertices
  int nCount // count of polygon's vertices
);
 
Parameters
hdc 
Handle to the device context. 
lpPoints 
Pointer to an array of POINT structures that specify the vertices of the polygon. 
nCount 
Specifies the number of vertices in the array. This value must be greater than or equal to 2. 
Return Values
If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero.

Windows NT: To get extended error information, callGetLastError. 

Remarks
The polygon is closed automatically by drawing a line from the last vertex to the first. 

The current position is neither used nor updated by the Polygon function. 

Windows CE: Windows CE version 1.0 supports only convex polygons. 

This function is the same in Windows CE version 2.0 as it is in Windows desktop platforms.

QuickInfo
  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  Header: Declared in wingdi.h.
  Import Library: Use gdi32.lib.

See Also
Filled Shapes Overview, Filled Shape Functions, GetPolyFillMode, POINT, Polyline, PolylineTo, PolyPolygon, SetPolyFillMode 

 

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不明白你说的意思
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模型？

你这是地形还是什么东西？ 如果是地形要挖洞的话，直接修改范围内顶点的高度值，使其凹进去就行了。


如果是模型，要把那块去掉的话，直接干掉范围内的三角形。 包括顶点和索引。

需要注意的是，我说的这2种方法都是近似效果，裁剪后效果跟模型表面的三角形数量有关系。
因为裁剪边界会经过某些三角形，如果需要精确显示的话，对这种被部分裁剪的地方，需要修补。通过移动顶点坐标和增加三角形(n边型划分为n-2个三角形)来实现。 


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