Can't enlarge vertex buffer

[thisredone]

after #5758 can't enlarge vertex buffers

bufferSubData throws when calling vertexBuffer.setData with bigger buffer. This breaks for example instancing

[mvaligursky]

The API was not designed to allow you to resize a VB this way, you need to re-create the VertexBuffer. You can always also create it larger and use only portion of it.
What you do worked by accident, and won't work on WebGPU for example.

[slimbuck]

See the base class https://github.com/playcanvas/engine/blob/main/src/platform/graphics/vertex-buffer.js#L139

[leonidaspir]

So if we are using instancing with e.g. a custom LOD and culling system I imagine the only way to use a dynamic buffer is by doing this per frame right, if the buffer has grown (works in v1.67.3):

    const vertexBuffer = new pc.VertexBuffer(
        this.app.graphicsDevice,
        pc.VertexFormat.defaultInstancingFormat,
        instancesCount,
        pc.BUFFER_STATIC,
        bufferArray
    );
    payload.meshInstance.setInstancing(vertexBuffer);

But if the buffer is smaller on a given frame and we try to use setData() with a smaller buffer then it fails with VertexBuffer: wrong initial data size: expected 2176, got 0:

        vertexBuffer.setData(bufferArray);

        payload.meshInstance.instancingData.count = instancesCount;
        vertexBuffer.numVertices = instancesCount;

This last bit worked with the previous version. Any other way to reuse a vertex buffer and avoid unnecessary garbage collection?

[mvaligursky]

the setData used to error for a long time now .. how were you using it without getting the errors?

I think what you should do is to call vb.Lock();, update partial data as needed, and then vb.unlock();
The number of instances for instancing can be then controlled using MeshInstance.instancingCount = 10;

[thisredone]

I was always updating buffer.byteLength when updating the contents so the Debug.error never came up ;-)