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My goal is to create a numpy array and convert its bytes data to QBuffer. I am wondering how to set properly DataSize, ByteStride, and Count. See my code below:

self.mesh = Qt3DRender.QGeometryRenderer()
self.mesh.setPrimitiveType(Qt3DRender.QGeometryRenderer.Points)
self.geometry = Qt3DRender.QGeometry(self.mesh)

vertex_data_buffer = Qt3DRender.QBuffer(Qt3DRender.QBuffer.VertexBuffer, self.geometry)
data = np.random.rand(1000, 3)
vertex_data_buffer.setData(QByteArray(data.tobytes()))

self.position_attribute = Qt3DRender.QAttribute()
self.position_attribute.setAttributeType(
    Qt3DRender.QAttribute.VertexAttribute)
self.position_attribute.setBuffer(vertex_data_buffer)
self.position_attribute.setDataType(Qt3DRender.QAttribute.Float)
self.position_attribute.setDataSize(3)  # ??
self.position_attribute.setByteOffset(0)
self.position_attribute.setByteStride(6)  # ??
self.position_attribute.setCount(1000)  # ??
self.position_attribute.setName(
    Qt3DRender.QAttribute.defaultPositionAttributeName())

self.geometry.addAttribute(self.position_attribute)
Vadim Kotov
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Matphy
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1 Answers1

2

We managed to fix this.

First of all these two copied below lines are deprecated. They can be removed.

self.position_attribute.setDataType(Qt3DRender.QAttribute.Float)
self.position_attribute.setDataSize(3)

One line is added: 

self.position_attribute.setVertexSize(3)

ByteStride should be set to 12. 3 is the number of coordinates and 4 is length of float32 in bytes. Be aware to set numpy's array: data = np.random.rand(1000, 3).astype(np.float32).

self.position_attribute.setByteOffset(0)
self.position_attribute.setByteStride(3*4)
self.position_attribute.setCount(1000)
Matphy
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