I'm using XNA but I assume the problem is analogous in DX9?

So I'm having a huge problem rendering a model that's created dynamically at runtime. It renders fine but it's creating a huge lag.

Here's the issue illustrated through a comparison:

1) Model with 10,000 vertices created in 3ds max and rendered with shader X in XNA ---> 200fps (after everything else has happened in the game)

2) Similar 10,000 vertex model constructed at runtime with a dynamic vertex buffer and rendered with shader X ---> 100fps

This is a completely unacceptable drop and I assume I'm doing something wrong. Something like minecraft would be impossible to run if this was a necessary drop. I can post my code if necessary but I'm just using the same approach used by the 3D particles sample. I've profiled the projected with NProf and all of the time is being spent in GraphicsDevice.Present()

Help?

Are you setting things up to get debug warnings? When I use a debug device in DX11 (I don't remember how that works in DX9) and I do something not completely legit, my framerate plummets from all the reporting of warnings every frame.

No, I'm not setting up any debug warnings. Like I say, I'm just using the same code found in the 3D particles sample from microsoft so there's really no room for me to be doing anything wrong in that sense. It must be more of a conceptual problem that I'm fundamentally missing.

And I've also tried using the 'NoOverwrite' option as described in Shawn Hargreaves' blog. No change.

Thanks for the reply Shaun, even if you called me cute (maybe I should change my avatar)

No, the SetData function is only called when necessary. Not every frame.
No, I didn't create the vertex buffer similarly for both models. I just use the inbuilt approach for rendering a model in the pre-fabricated example. I wasn't making the comparison to say they should be identical in the frame rate. If the run-time version was at 180fps or something, I'd just assume that was a necessary price to pay. But 100fps seems criminal. Otherwise, the vertex types and shaders are the same.

I don't think Microsofts codes are necessarily the best. But the fact that I've used that particular 3D particle sample a lot, and have found it performs very nicely, seems to be a good sign.

Cool, I'll have a read through that page.

Yep, those flags are all set (or their equivalents in XNA) and I've tried with the Discard option.

I'm not calling createvertexbuffer every frame, just once at the beginning. I'm not entirely clear on the part where you say "careful that you don't attempt to read from the buffer while you have it locked". What do you mean by 'read' in this context? As I say, the model is dynamically being added to. But not each frame.

The vertex creation CPU side it quite simple. There are about 4-6 base models that I'm combining to make a larger structure. Those base models are loaded into vertex and index arrays at the beginning. Based on the user input, these base arrays are then combined into the larger array which is set to the vertex/index buffers when it's changed.

From what you've mentioned seems like you are not doing anything out of the ordinary. Do you have the actual draw timings for comparison?, FPS is reliable performance metric especially when developing.

What do you mean by the draw timings? As in, the number of ms taken in the Present() function?

Why will that give any more info than the FPS I've already mentioned? Everything else about the solution is identical.