Could someone please explain the best way to use vertex arrays.
I am writing a 3D engine, each surface has an array of vertices, normals and
indices. Should I:
a) Create one huge vertex/normal/.. array with
glVertexPointer/glNormalPointer when I start up then use glDrawElements
giving an offset to each objects indices each frame?
b) use many smaller glVertexPointer's which are called each frame?
when is data actually copied across to the card? glDrawElements?

Many regards


Mike

Michael wrote:
> Could someone please explain the best way to use vertex arrays.
> I am writing a 3D engine, each surface has an array of vertices, normals and
> indices. Should I:
> a) Create one huge vertex/normal/.. array with
> glVertexPointer/glNormalPointer when I start up then use glDrawElements
> giving an offset to each objects indices each frame?
> b) use many smaller glVertexPointer's which are called each frame?

There's no right answer to that, it depends:

a) On your graphics card - a big array might not
fit on the graphics card all at once.

b) On your program - if you're culling objects
against the view then only a small part of
the vertices are needed. If you make one big
array then you're transferring a lot of useless
vertices.


> when is data actually copied across to the card? glDrawElements?
> 

Again, it depends on the driver.

The vertex_buffer_object extension lets you put the
arrays on the card so they never need copying.


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Michael wrote:

> Could someone please explain the best way to use vertex arrays.
> I am writing a 3D engine, each surface has an array of
> vertices, normals and indices. Should I:

Depends, as so often in OpenGL.

> a) Create one huge vertex/normal/.. array with
> glVertexPointer/glNormalPointer when I start up then use
> glDrawElements giving an offset to each objects indices each
> frame?

This is probably the right method if you want to draw a lot of
different, not too complex objects, sharing the texture(s), e.g.
plants or particle systems. Actually it's robably the best
method for particle systems.

> b) use many smaller glVertexPointer's which are called 
> each frame? when is data actually copied across to the card?
> glDrawElements?

IMHO the better method for rather complex objects having >=500
vertices.

Suggestion: Use the capabilities of modern GPUs. E.g. in our game
there are only about 10 different base meshes for humans,
however every character looks different. The magic behind it:
For every character's body a set of "morphers" is set globally.
These morphers control mesh deformation in a vertex program.
Currently there are 6 morphers
- arm strengh
- leg strengh
- fat
- muscle
- proportion1
- proportion2
and as every NPC has slightly different morphers they look all
different. The head itself has it's own set of morphers, as
these also have their own influence on look and mimic system's
bones.

Wolfgang