Union collision issue

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#1

Hello dear developers,Im an game builder with lua scripter.Im trying to do a fanmade rooms game for fun but im having an issue about unions.I needed union for this so i decided to do it,i thought everything was fine then this collision issue started happening.

resim
resim1280×1024 120 KB

As you can see even door is opened i cannot pass through the hole.Theres nothing blocking the path.Only i can pass through after disabling union collisions.But this also affects the whole union model.

Anybody can help me about this issue? I cannot test my game for real because of this.

#2

maybe try setting the collision fidelity to precise

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#3

Omg it worked i didnt thought it was easy because when i read it on other forums my brain couldnt handle it :smiley:

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#4

I would suggest not using unions at all as they make your game even worse. It’s better to stick with parts.

#5

but parts also making my game really laggy.with all unions im having 130 fps but with parts it making the game worse only 50 fps

#6

Seems to be an issue with your computer. It has been proven by experiments that unions cause more issues as it makes useless triangles. If you were to union three parts then it would make more than 36 triangles which would be the amount of 3 normal parts. You could see it by exporting the unioned mesh to blender and such.

#7

unions are better for his case
36 extra triangles for a door is nothing in fact it will increase his game performance because it will have to make 1 draw call instead of 2+

if you will make simple builds then go for unions
if you will make complex objects then itsnot good to use unions for that nor parts it would be better to make it as a mesh in external 3d software so you can optimize the faces

#8

I disagree. For my game. Such unions caused more lag then any good. It is also to note that collisions can be hectic with unions.

#9

if you used them to make complex builds then it will make lag but it willnot cause any problems for simple builds

#10

I am talking about simple builds. With unions. Roblox has to do more collision computing.

#11

you are right about that unions arnot that good for lighting/physics But for simple builds it improve performance by reducing draw calls an object with 100 triangles is nothing for any low end gpu what will matter more is the number of draw calls

#12

Then it could be better said that unions are only good for objects that are meant to have collisions off and not for those that will have collisions.

#13

collisions shouldnot be a problem for an object with 100 triangles
a door union with 100 triangles and 1 draw call is alot better than a door with 50 triangles and 6 draw calls
unions will add more triangles but it is better than having 6 parts for a door because of drawcalls

#14

Won’t having more triangles already mitigate the effect of more draw calls.? I saw a video by @iGottic about effects of unions. Maybe check that out. Ill just say that for me, and for OP unions are pretty bad because of collisions issues and unnecessary triangles. At such a point, OP should resolve to using blender to make such a mesh which would lower the triangle count by a staggering amount.

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#15

i just checked that video rn he used complex objects in his build like sphere + part + part
its still better having a model few extra triangles rather than having alot of draw calls
an old phone like iphone 6 can render up to 500k triangles what really matter is draw calls because they can cuase performance bottlenecks
i would rather use a door with 1000 triangles and 1 draw calls rather than a model with 200 triangles and 20 draw calls

#16

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