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发表于 2006-4-24 10:13:00
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Re:如何实现opengl中图形的加减
opengl只提供基本图形的绘制，复杂图形要自己编写代码或者利用材质来达到同样的效果。
glBegin, glEnd
The glBegin and glEnd functions delimit the vertices of a primitive or a group of like primitives.
void glBegin(
GLenum mode
);
void glEnd(
void
);
Parameters
mode
The primitive or primitives that will be created from vertices presented between glBegin and the subsequent glEnd. The following are accepted symbolic constants and their meanings:
GL_POINTS
Treats each vertex as a single point. Vertex n defines point n. N points are drawn.
GL_LINES
Treats each pair of vertices as an independent line segment. Vertices 2n ? 1 and 2n define line n. N/2 lines are drawn.
GL_LINE_STRIP
Draws a connected group of line segments from the first vertex to the last. Vertices n and n+1 define line n. N ? 1 lines are drawn.
GL_LINE_LOOP
Draws a connected group of line segments from the first vertex to the last, then back to the first. Vertices n and n+1 define line n. The last line, however, is defined by vertices N and 1. N lines are drawn.
GL_TRIANGLES
Treats each triplet of vertices as an independent triangle. Vertices 3n ? 2, 3n ?1, and 3n define triangle n. N/3 triangles are drawn.
GL_TRIANGLE_STRIP
Draws a connected group of triangles. One triangle is defined for each vertex presented after the first two vertices. For odd n, vertices n, n + 1, and n + 2 define triangle n. For even n, vertices n + 1, n, and n + 2 define triangle n. N ? 2 triangles are drawn.
GL_TRIANGLE_FAN
Draws a connected group of triangles. One triangle is defined for each vertex presented after the first two vertices. Vertices 1, n + 1, and n + 2 define triangle n. N ? 2 triangles are drawn.
GL_QUADS
Treats each group of four vertices as an independent quadrilateral. Vertices 4n ? 3, 4n ? 2, 4n ? 1, and 4n define quadrilateral n. N/4 quadrilaterals are drawn.
GL_QUAD_STRIP
Draws a connected group of quadrilaterals. One quadrilateral is defined for each pair of vertices presented after the first pair. Vertices 2n ? 1, 2n, 2n + 2, and 2n + 1 define quadrilateral n. N quadrilaterals are drawn. Note that the order in which vertices are used to construct a quadrilateral from strip data is different from that used with independent data.
GL_POLYGON
Draws a single, convex polygon. Vertices 1 through N define this polygon.
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