vertex array的用法

zhuyi8319

请高手　简单的解释一下　vertex array的　用法，感激不尽．．

zhuyi8319

How can I use vertex arrays to share vertices
?

Because vertex arrays let you access a set of vertices and data by index, you might believe that they're designed to optimally share vertices. Indeed, a programmer new to vertex arrays might try to render a cube, in which each vertex is shared by three faces. The futility of this becomes obvious when you add normals for lighting and each instance of the shared vertex requires a unique normal. The only way to render a cube with normals is to include multiple copies of each vertex.

Vertex arrays weren't designed to improve vertex sharing. They were intended to let the programmer to specify blocks of dynamic geometry data with as few function calls as possible.

You can share vertices with vertex arrays the same way you do with OpenGL immediate mode, by the type of primitive used. GL_LINE_STRIP, GL_LINE_LOOP, GL_TRIANGLE_STRIP, and GL_QUAD_STRIP share vertices between their component line segments, triangles, and quads. Other primitives do not. The type of primitive you choose to use when using vertex arrays determines whether you share vertices.

Note, however, that sharing vertices is implementation dependent. The OpenGL Specification dictates vertex array behavior, and as long as an OpenGL implementation conforms to spec, it's free to optimize vertex sharing in vertex arrays.

Some implementations feature the EXT_compiled_vertex_array extension, which is explicitly designed to let implementations share transformed vertex array data.

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zhuyi8319

上面好象说 vertex arrays 没什么用,因为光照处理的时候还是需要对每个 vertex计算法线的,
不过可以用来 做terrain ,呵呵,请高手在补充,修正一下我的观点,

dfq19

www.codesampler.com 有例子

zhuyi8319

好网站,收藏了,多谢,