Game Processing Order
From Multi Theft Auto: Wiki
Game processing order
Here is an overview to show the order in which things get done during an average frame of playing MTA.
The onClientPreRender event is triggered after GTA updates the world, and is the ideal place to do dxDraws that are in some way attached to world elements.
The onClientHUDRender event is triggered before GTA renders the in-game HUD, so it the best place to apply any full screen effects that you want 'behind' the HUD.