Dynamic Vertex Buffers

Here is a screenshot of a demo application I created to show the new dynamic features of the vertex/index buffer interface. It displays a patch field the uses a sine wave to calculate the new positions of each vertex on each interation of the application loop. The effect is a rippling effect from the center of the patch to the end. Also, the red diffuse color is adjusted to become more intense at the high wave peak and less intense at the wave down peak. All of these effects are scaled by time to create a smooth animation. You can enjoy the demo by clicking here

I have modified the vertex/index buffers to support both static and dynamic propertics. The demo above show the nature of using dynamic vertex buffers. This allows the client to modify the vertices in the vertex buffer at any time. There are two conditions to be aware of, an overwrite vertex buffer and a nooverwrite vertex buffer.

The overwrite vertex buffer will discard the vertices in the vertex buffer and write the new vertices starting at the beginning of the buffer. Since the Graphics Processing Unit (GPU) will be expecting this to occur, it will return a new pointer into the buffer for the client to add vertices to and then discard the previous vertices.

The nooverwrite vertex buffer will only return a pointer to the available space remaining in the vertex buffer to add the new vertices to. The catch is, if there isn't enough space to add the new vertices, then the vertex buffer will move into overwrite mode and will function like an overwrite vertex buffer. The vertex buffer will return an error when this occurs to let the client know it is no longer protecting the original vertices. This will give the client an opportunity to either continue rendering without crashing or to recreate the vertex buffer to add more space to it. The best approach when using a nooverwrite vertex buffer is to check for enough space before adding the vertices.

Also, to run the demo your video card must support the use of dynamic vertex buffering. The demo doesn't use extensive error handling. I will update the code to be a bit more user-friendly, but its main purpose is to demonstate the use of the Dynamic Vertex Buffer interface. Enjoy!

That's all for now...I am coming with more updates, so stay tuned!

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