这个方法用于给着色器中指定的变量设置每个顶点属性及三个元素的值的取值指针起始位置。
要达到此目的，需要开启以下三个属性，参数就是着色器中的要获取顶点属性各元素的变量。
glEnableVertexAttribArray(_textureCoordSlot);
glEnableVertexAttribArray(_positionSlot);
glEnableVertexAttribArray(_normalSlot);
真不知，一知半解的，我是怎么实现之前那些东西的！
回想起来，还是得感谢老罗前辈，至少在 OpenGLES 方面，确实是位值得称道的前辈。
心怀感恩，觉得随处可以见到曾经的贵人，这种感觉真的很好，谢谢贵人们。
Name
glVertexAttribPointer — define an array of generic vertex attribute data
C Specification
void glVertexAttribPointer( |
GLuint index, |
| GLint size, | |
| GLenum type, | |
| GLboolean normalized, | |
| GLsizei stride, | |
const GLvoid * pointer); |
Parameters
-
index -
Specifies the index of the generic vertex attribute to be modified.
-
size -
Specifies the number of components per generic vertex attribute. Must be 1, 2, 3, or 4. The initial value is 4.
-
type -
Specifies the data type of each component in the array. Symbolic constants
GL_BYTE,GL_UNSIGNED_BYTE,GL_SHORT,GL_UNSIGNED_SHORT,GL_FIXED, orGL_FLOATare accepted. The initial value isGL_FLOAT. -
normalized -
Specifies whether fixed-point data values should be normalized (
GL_TRUE) or converted directly as fixed-point values (GL_FALSE) when they are accessed. -
stride -
Specifies the byte offset between consecutive generic vertex attributes. If
strideis 0, the generic vertex attributes are understood to be tightly packed in the array. The initial value is 0. -
pointer -
Specifies a pointer to the first component of the first generic vertex attribute in the array. The initial value is 0.
Description
glVertexAttribPointer specifies the location and data format of the array of generic vertex attributes at index index to use when rendering. size specifies the number of components per attribute and must be 1, 2, 3, or 4. type specifies the data type of each component, and stride specifies the byte stride from one attribute to the next, allowing vertices and attributes to be packed into a single array or stored in separate arrays. If set to GL_TRUE, normalized indicates that values stored in an integer format are to be mapped to the range [-1,1] (for signed values) or [0,1] (for unsigned values) when they are accessed and converted to floating point. Otherwise, values will be converted to floats directly without normalization.
If a non-zero named buffer object is bound to the GL_ARRAY_BUFFER target (see glBindBuffer) while a generic vertex attribute array is specified, pointer is treated as a byte offset into the buffer object's data store. Also, the buffer object binding (GL_ARRAY_BUFFER_BINDING) is saved as generic vertex attribute array client-side state (GL_VERTEX_ATTRIB_ARRAY_BUFFER_BINDING) for index index.
When a generic vertex attribute array is specified, size, type, normalized, stride, and pointer are saved as client-side state, in addition to the current vertex array buffer object binding.
To enable and disable a generic vertex attribute array, call glEnableVertexAttribArray and glDisableVertexAttribArray with index. If enabled, the generic vertex attribute array is used when glDrawArrays or glDrawElements is called.
Notes
Each generic vertex attribute array is initially disabled and isn't accessed when glDrawElements or glDrawArrays is called.
glVertexAttribPointer is typically implemented on the client side.
Errors
GL_INVALID_ENUM is generated if type is not an accepted value.
GL_INVALID_VALUE is generated if index is greater than or equal to GL_MAX_VERTEX_ATTRIBS.
GL_INVALID_VALUE is generated if size is not 1, 2, 3, or 4.
GL_INVALID_VALUE is generated if stride is negative.
Associated Gets
glGet with argument GL_MAX_VERTEX_ATTRIBS
glGetVertexAttrib with arguments index and GL_VERTEX_ATTRIB_ARRAY_ENABLED
glGetVertexAttrib with arguments index and GL_VERTEX_ATTRIB_ARRAY_SIZE
glGetVertexAttrib with arguments index and GL_VERTEX_ATTRIB_ARRAY_TYPE
glGetVertexAttrib with arguments index and GL_VERTEX_ATTRIB_ARRAY_NORMALIZED
glGetVertexAttrib with arguments index and GL_VERTEX_ATTRIB_ARRAY_STRIDE
glGetVertexAttrib with arguments index and GL_VERTEX_ATTRIB_ARRAY_BUFFER_BINDING
glGet with argument GL_ARRAY_BUFFER_BINDING
glGetVertexAttribPointerv with arguments index and GL_VERTEX_ATTRIB_ARRAY_POINTER
See Also
glBindAttribLocation, glBindBuffer, glDisableVertexAttribArray, glDrawArrays, glDrawElements, glEnableVertexAttribArray, glVertexAttribCopyright
Copyright © 2003-2005 3Dlabs Inc. Ltd. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/.
