Reduces memory allocations on render path/hot path

[tippesi]

There are quite a number of unnecessary memory allocation on hot paths that could be moved on the stack.
This really hurts in multi-threading cases when other threads allocate a lot of memory.

Ideas for improvements:

• Pipeline barriers should not use std::vector
• Blur filter weights can be calculated in constructors
• Basically all usages of std::vector where we resize on a regular basis or even worse use .push_back without a proper .reserve

[YanbingXu]

您好，我已收到邮件，谢谢！