How a simple idea can save big – Understanding the Forward Vector and Coordinate System
Forward Vector
Have you ever encountered a situation where the muzzle flash appears not in front of the barrel but off to the side? Have you seen sets of similar effects oriented along different axes? Did the team have to reorient the effects? How much time did it take?
Have you worked with modular building kits? Have you come across elements with different orientations that make automation difficult or even impossible? How did you solve this issue? Did you add the ability to adjust asset orientation everywhere, or do you do it manually? The challenges of procedural shading. People underestimate the impact of inconsistency.
I want to talk about how to eliminate this problem once and for all.
You'll be surprised how much time you can save by setting up rules in pre-production. When I first set up the rules for importing models and orienting particle systems, I did some work. To find the right solution for declare a universal Forward Vector for the project, I analyzed all aspects related to the Forward Vector in the Unreal Engine.
Material Decal positive X - oriented;
Particle System positive X - oriented;
Camera positive X - oriented;
Player Start positive X - oriented;
It may seem that positive X is the perfect candidate. But historically, Skeletal Meshes are positive Y - oriented, all Character meshes rotation always (X = 0, Y = 0, Z = -90);
I tried to find the answer in the materials. Object Orientation material node return local positive Z (Up Vector). The Epics avoided choice in favor of universality
I will also try to give a universal answer: The Forward Vector for the Static Mesh should be positive X. If the moment is missed and already positive Y it is ok, but both cannot be used simultaneously. For particles it is already positive X, you just need to correctly build the effect along this axis. The employee should not have any doubts about how the effect or model is oriented, he should not rotate anything.
By setting up a dedicated Confluence page for the forward vectors of various entities and providing access to modelers, VFX artists, technical designers, and programmers, you can significantly streamline communication and save your team a considerable amount of time.
Coordinate System
Unreal Engine has a Y-up, Left Handed Coordinate System. There are 12 possible axis configurations in total: Left Handed X-up, Y-up, Z-up, X-down, Y-down, Z-down and Right Handed X-up, Y-up, Z-up, X-down, Y-down, Z-down. But most software only uses four possible axis configurations.
All you need to do when using your fingers—whether they belong to your left or right hand—is to associate the X-axis with your thumb, the Y-axis with your index finger, and the Z-axis with your middle finger. That's it. When working with procedural geometry, animation, or geometry cache, it is very useful to have a clear understanding of the differences between axis configurations.