[英]How does OpenGL know to what position it should draw the vertices based on the GL_ARRAY_BUFFER?
For example, I have the following piece of code: 例如,我有以下代码:
//Create a vbo and bind it to the GL_ARRAY_BUFFER
glGenBuffers(1, &positionBufferObject);
glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);
//vertexPosition is an array of floats that stores the position of 3 vertices (x, y, z, w)
glBufferData(GL_ARRAY_BUFFER, sizeof(vertexPositions), vertexPositions, GL_STATIC_DRAW);
//Enable the vbo at index 0 of the vao (assuming I have stored it previously at index 0)
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
//Finally draw the triangle
glDrawArrays(GL_TRIANGLES, 0, 3);
My question is, how does glDrawArrays() know that whatever is bound to the GL_ARRAY_BUFFER refers to information about position, and not about colors for example? 我的问题是,glDrawArrays()如何知道绑定到GL_ARRAY_BUFFER的内容是指位置信息,而不是颜色信息?
Where gl_Vertex
is available (ie not a core profile), the specification calls out that position and vertex attribute 0 alias. 如果gl_Vertex
可用(即没有核心配置文件),则规范会调用该位置和顶点属性0别名。
From the gl 4.5 compatibility profile specification (page 401/1005): 从gl 4.5兼容性配置文件规范 (第401/1005页):
Setting generic vertex attribute zero specifies a vertex, as described in section 10.7.2. 将通用顶点属性设置为零会指定一个顶点,如10.7.2节所述。 Setting any other generic vertex attribute updates the current values of the attribute. 设置任何其他通用顶点属性将更新该属性的当前值。 There are no current values for vertex attribute zero 顶点属性零没有当前值
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