array vs pointer to array question

[santiagorf]

Hi,
I'm confused about the following situation:

The following code when I use an array works fine

//declare vertex
glm::vec2 vertex[1000];   //a very large size

//load the vertex
...

//send vertex to buffer
glBufferSubData( GL_ARRAY_BUFFER, 0 ,sizeof(vertex[0])*vertexSize,vertex );

but if I use a pointer to array

//declare vertex
glm::vec2 * vertex;


//allocate vertex
vertex = new glm::vec2[vertexSize];

//load the vertex
...

//send vertex to buffer
glBufferSubData( GL_ARRAY_BUFFER, 0 ,sizeof(vertex[0])*vertexSize,vertex );

the code does not work as intended.

What I'm doing wrong?

From the openGL reference, the signature of the method is:
void glBufferSubData( GLenum target, GLintptr offset, GLsizeiptr size, const GLvoid * data);

thanks in advance

[Peter87]

What is waterVertex?

[santiagorf]

ups...waterVertex is of the same type as vertex.

[Peter87]

And vertexSize does not change between the array is allocated and glBufferSubData is called?

[giblit]

the code does not work as intended.

Will you be a little more specific please.

[santiagorf]

vertexSize, once set, remains constant during the whole program, but it is unknown at compile time
When I use a pointer to array, the screen is blank as if no data was copied to the opengl array buffer.

I have printed vertex in both examples before calling glBufferSubData to check if they contain the same data, and they do. That's why I was thinking that there is something wrong between glBufferSubData and glm::vec2 * vertex.