Set all data related to the instances in one go. This is especially useful when loading the data from disk or preparing the data from GDNative.
All data is packed in one large float array. An array may look like this: Transform for instance 1, color data for instance 1, custom data for instance 1, transform for instance 2, color data for instance 2, etc...
[Transform] is stored as 12 floats, [Transform2D] is stored as 8 floats, COLOR_8BIT / CUSTOM_DATA_8BIT is stored as 1 float (4 bytes as is) and COLOR_FLOAT / CUSTOM_DATA_FLOAT is stored as 4 floats.
Number of instances that will get drawn. This clears and (re)sizes the buffers. By default all instances are drawn but you can limit this with [member visible_instance_count].