问题描述
有
glVertexAttribPointer()
glVertexAttribIPointer()
glVertexAttribLPointer()
据我所知，可以使用 glVertexAttribPointer 代替其他两个.
As far as I know, glVertexAttribPointer can be used instead of the other two.
如果是这样，为什么会存在 I 和 L 变体?
If so, why do the I and L variations exist?
推荐答案
我在 OpenGL Insights 中读到了相关内容
I read about this in OpenGL Insights
当使用 glVertexAttribPointer() 时，一切都会被转换为浮点数.glVertexAttribIPointer() 只能公开存储整数的顶点数组，而 glVertexAttribLPointer() 仅用于双精度数.
When using glVertexAttribPointer() everything gets cast to a float. While glVertexAttribIPointer() can only expose vertex arrays that store integers and glVertexAttribLPointer() is only for doubles.
正如此 OpenGL.org 页面上的引用所证实:
As confirmed by a quote on this OpenGL.org page:
对于 glVertexAttribPointer，如果 normalized 设置为 GL_TRUE，则表示以整数格式存储的值将被映射到范围 [-1,1](对于有符号值)或 [0,1](对于无符号值)当它们被访问并转换为浮点时.否则，值将直接转换为浮点数，无需标准化.
对于 glVertexAttribIPointer，只有整数类型 GL_BYTE，GL_UNSIGNED_BYTE、GL_SHORT、GL_UNSIGNED_SHORT、GL_INT、接受 GL_UNSIGNED_INT.值始终保留为整数值.
For glVertexAttribIPointer, only the integer types GL_BYTE, GL_UNSIGNED_BYTE, GL_SHORT, GL_UNSIGNED_SHORT, GL_INT, GL_UNSIGNED_INT are accepted. Values are always left as integer values.
glVertexAttribLPointer 指定通用顶点属性的状态与使用 64 位声明的着色器属性变量关联的数组双精度元件.类型必须是 GL_DOUBLE.索引，大小，和 stride 的行为与 glVertexAttribPointer 和glVertexAttribIPointer.
glVertexAttribLPointer specifies state for a generic vertex attribute array associated with a shader attribute variable declared with 64-bit double precision components. type must be GL_DOUBLE. index, size, and stride behave as described for glVertexAttribPointer and glVertexAttribIPointer.
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