0. Pipeline

Workflow

Definition: We provide the GPU with the data that we need to draw and store them into the cache of GPU.

1. Vertex Attributes

1

glVertexAttribPointer

[!note] Clarification of vertex
vertex is not just about position,it can contain bunch of things.Like color and other things.

2. Buffer layout

This things shoudl be done before the bind.
Defintion: Just like the normal cpp code,we need to tell the shader what is the thing that each part of the cache represents.

Code achievements

glVertexAttriPointer

Document

Parameters(In the document)

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, 4. Additionally, the symbolic constant GL_BGRA is accepted by glVertexAttribPointer. The initial value is 4.

type
Specifies the data type of each component in the array. The symbolic constants GL_BYTE, GL_UNSIGNED_BYTE, GL_SHORT, GL_UNSIGNED_SHORT, GL_INT, and GL_UNSIGNED_INT are accepted by glVertexAttribPointer and glVertexAttribIPointer.
Additionally GL_HALF_FLOAT, GL_FLOAT, GL_DOUBLE, GL_FIXED, GL_INT_2_10_10_10_REV, GL_UNSIGNED_INT_2_10_10_10_REV and GL_UNSIGNED_INT_10F_11F_11F_REV are accepted by glVertexAttribPointer. GL_DOUBLE is also accepted by glVertexAttribLPointer and is the only token accepted by the type parameter for that function. The initial value is GL_FLOAT.

normalized 同一化
For glVertexAttribPointer, 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 步幅-每个顶点之间的字节偏移量（也就是每个步之间属性所占的字节大小）
Specifies the byte offset between consecutive generic vertex attributes. If stride is 0, the generic vertex attributes are understood to be tightly packed in the array. The initial value is 0.

[!Note] Macro to help
In order to calculate the number of the stride , we often need to manually count them , which may lead to mistakes.
So we can use macro to represent the number,and use them to get rid of the trouble

pointer
Specifies a offset of the first component of the first generic vertex attribute in the array in the data store of the buffer currently bound to the GL_ARRAY_BUFFER target. The initial value is 0.

1

(const void*)8

IF the offset is 8 bytes, you write it this way, since it requires void*.

glEnableVertexAttribArray

After you set the attrib , you need to call this function to enable it.

1
2

void glEnableVertexAttribArray(GLuint index);
void glDisableVertexAttribArray(GLuint index);

The index in this parameter is exactly the first parm in glVertexAttriPointer.