Why is "Simulate physics" sometimes grayed out?

Hello!

Every so often I’m trying to test a concept out, and something infuriating happens: the engine does not let me turn on t he physics simulation.
This time I did the following:

start up UE4, choose blank project.
import a cube made in blender and exported as an FBX file.
attach a material to it (simply a solid colour).
attach it to a blueprint
Profi… cough problem! Physics is grayed out.

What I was going to test how the engine handles tens, if not hundreds of t housands of cubes in a scene, wheter it is even capable of running with them, and what if each of those cubes were physically simulated. These tests were to explore different techniques to make a voxel game, and the performance hit from objects that are not actively rendered.

What is it making me unable to use physics, and does anyone have any knowledge that I was trying to obtain by the tests? (I am currently testing how it runs without physics)

Hi DoctorPC,

When using a mesh in your BP you’ll need to make sure that there is collision setup. If there is no Collision it will leave the check box grayed out.

Give this a shot and let me know if this resolved it for you! :slight_smile:

Tim

all right, thanks! (Not sure if this makes sense though, I could see someone wanting physics to collisionless object, while it would only apply gravity…, well luckily that’s not my goal)

Just as a fun fact, if you wanted to do that you could set the collision to ignore all or overlap all and simulate physics with gravity enabled.