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VBOs and std::vector

Started by Ainokea Feb 27, 2005 at 6:24 PM 6 replies 850+ views

Original Post

Feb 27, 2005 at 6:24 PM

Previously I used to use pointers to contain things like vertex data instead of vectors, I would do something like this:


Vertex *verts;

//instead of something like this:
std::vector<Vertex> verts;

Then it would be easy to work with VBOs because I could do something like this:


glBufferDataARB(GL_ARRAY_BUFFER_ARB,numVerts*3*sizeof(float),verts,GL_STATIC_DRAW_ARB);


But if I where to store my vertex data inside of a vector I don't know what I would pass off to the function where I previously would have put verts.

_the_phantom_

Feb 27, 2005 at 6:29 PM

the std::vector is garrenteed (as per the last spec update) to have contigous memory allocation, so you pass the address of the first element as the source for the data (as &verts[0], might require some casting).

I've used it myself a few times now, works perfectly, you can even use the size function of the container to setup the data size properly [grin] (verts.size()*sizeof(Vertex) gives you the total memory size)

nts

Feb 27, 2005 at 6:29 PM

you need a pointer to the data, the following should work

void* ptr = &verts[0];   // or use verts.at(0)

gets a pointer to the first element and assuming everything is stored sequentially (AFAIK it is) then that should act exactly like the verts array you used before.

HTH

Ainokea

Feb 27, 2005 at 6:40 PM

Thanks! Ratings++ to both of you, unless I did it already!

Icy Earth

Feb 27, 2005 at 7:36 PM

dont forget &verts.front() i prefer that myself so i thought id throw it out there :-)

-Dan

Ainokea

Feb 27, 2005 at 7:47 PM

Quote:
Original post by Icy Earth
dont forget &verts.front() i prefer that myself so i thought id throw it out there :-)

-Dan

I actually did that anyways, thanks anyways and ratings++ too!

WilyCoder

Feb 27, 2005 at 10:06 PM

I've always wondered what a void pointer is....

Is it a pointer to an abstract piece of data?

When using them, should you also use a variable to conatin the stepping size?

Ademan555

Feb 27, 2005 at 10:19 PM

a void pointer should be thought of like a pointer in assembly, what it points to is undefined, it has no type untill you cast it to give it a type, incrementing it moves it one machine unit (byte)

hope that helps
-Dan

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