4.17.x Production Quality Build breaking physics

[Neil_London]

So I’ve come across this a couple of times and I’ve noticed that when ever I do a Production Quality Build my physics start breaking. When I do a preview build everything works fine. What is happening is I am taking courses on Learning the Engine and we are making a Pinball game. I’m at about 90% completed with the section and the game before moving on to the next section which is a different type of game. Since This was my first time in Unreal I got the latest version because you know… The latest and greatest right?

Well now that I’ve built my game and designed the Table, placed lights, lightmass boxes, balanced the physics, created the scoring system and a way to save the scores in a high score chart, I go to do a production quality build to make my game look pretty and suddenly the ball randomly moves in a random direction without getting hit, when it sits at the plunger it starts to shake when it didn’t before, the collisions and impulse nodes don’t work correctly or launch the ball in the opposite direction at 10x the speed it should have been launched. I move a light 1 unit and back do a Preview Quality Build and the physics are back to normal and working correctly. Do A production build, broken physics, go back to Preview, physics are fine. I’ve tried this about 6-7 different times and it has happened every time. Is this a bug because this version of the Engine is so new? Should I do the next section on 4.16.3 or an earlier version then that? Are other people experiencing this? If this was just a one time fluke or even an issue with a blueprint I’d either rebuild the BP or scrap the mechanic but its the ball… you kinda need a ball to function in pinball. I’m not made just frustrated at not understanding why the physics change, or maybe just things are reacting differently, from Preview build to Production Build. I started with 4.17.0 then updated to 4.17.1 and it’s in both versions.

Any help would be a big thanks! I’ve only been learning Unreal for about a month and have 0 game dev experience.

Thanks in advanced!

[Allottho]

Thought that I was experiencing same issue, but after trying to reproduce in clean project, I finally remembered a way of testing what’s affecting your physics object blueprint. Try this and look into log. Look for unexpected actor names and too big impulse normal coordinates (like more than 100. Around 15-40 is a “lying still” impulse for active physics object lying on the floor).
Maybe some collision checkbox or preset gone crazy, or collision on some mesh reset to auto-generated convex. Sounds far-fetched in your situation, but who knows. At least, you can test and see.
I hope it helps.

[Neil_London]

In the end I figured out it was because I had a lot of mobile lights for flickering and such. I’m guess the lights were taking up all the processing power causing the physics to take a back seat then it would register them and when it would the ball was clipped through the table and launching it off into space as a result. I’ve learned a lot since then so I know I wont make mistake again.