This is usually not done like this. GeometricPrimitives are immutable data because they better fit the way the GPU is optimized for them. Usually if you need dynamic scenario for modifying vertices, you can either implement the resize logic in a custom vertex shader with a World/Object Matrix that can scale the object (so that the initial vertex buffer doesn't change). You can do that basically with a BasicEffect with a specific World matrix.
For other dynamic requirements (list of vertices changing often...etc.), they are too specific to be generalized but the API provides a way to create your custom vertex/index dynamic buffer...etc.

So sorry, GeometricPrimitives should stay immutable.

Got it, that makes sense.
Thanks

On May 2, 2014, at 12:15 AM, "Alexandre Mutel" notifications@github.com wrote:

This is usually not done like this. GeometricPrimitives are immutable data because they better fit the way the GPU is optimized for them. Usually if you need dynamic scenario for modifying vertices, you can either implement the resize logic in a custom vertex shader with a World/Object Matrix that can scale the object (so that the initial vertex buffer doesn't change). You can do that basically with a BasicEffect with a specific World matrix.
For other dynamic requirements (list of vertices changing often...etc.), they are too specific to be generalized but the API provides a way to create your custom vertex/index dynamic buffer...etc.

So sorry, GeometricPrimitives should stay immutable.

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