Play Solo: Motors can cause rendering bugs

Bug Reports Studio Bugs
1

This is a really odd bug, and has been present for 9 months (Contacted info@roblox, they said they’d forward; who knows what happened with that).

The parts can expand, defy Lighting, stretch; ect. But, they will still interact properly with Other parts. Dragging a model with these parts show’s their true form.

This bug was found by multiplying the default character’s offsets by 2 (Adding .1 also worked).
Merely generating 1s or 2s for the offsets caused this bug.

Making the C0/C1 simplifed (Just the Position), parts would not render at all.

Steps to repro:
[ol]
[li]Use Motors[/li]
[li]Set the C0/C1 in an absurd manner. (Could be at random).[/li]
[li]Use Play Solo (Or just “Play”)[/li]
[/ol]

How it should look (Server):
External Media

How it looks in local testing (Play solo):

Some of the original code is intact, but a few scripts were added to demonstrate the bug.

2

Characters use Motor6D, do they not?

3

All motors break. That has nothing to do with it, it’d be very odd if it had.

4

You are setting CFrame rotation matrices whose determinant is greater than 1.

That is not okay. Why are you doing this. What are you trying to do?

local RightShoulder = Instance.new("Motor")
RightShoulder.Name = "Right Shoulder"
RightShoulder.Part0 = Torso
RightShoulder.Part1 = Character["Right Arm"]
RightShoulder.C0 = CFrame.new(2, 1, 0, 0, 0, 2, 0, 2, -0, -2, 0, 0)
RightShoulder.C1 = CFrame.new(-1, 1, 0, 0, 0, 2, 0, 2, -0, -2, 0, 0)
RightShoulder.Parent = Torso

Never do this.

You are basically saying that

RightShoulder.C0 = CFrame.new(2, 1, 0, 0, 0, 2, 0, 2, -0, -2, 0, 0)
     [0, 0,  2]
R1 = [0, 2, -0]
     [-2, 0, 0]

is your rotation matrix, which has a determinant > 1. This causes reality to warp in creepy ways, enlarging your parts.

Rotation Matrices

5

I did note it was an old place, but good for future reference.

I had just multiplied the default offsets for players 9 months back when I was experimenting with larger characters, didn’t really think of the impact.

6

Also:

The reason we do check these Det of the matrix for you is because if we had to run a det math operation every time someone changed a CFrame, you would enjoy a lovely slow-motion game most of the time.

7

[quote] Also:

The reason we do check these Det of the matrix for you is because if we had to run a det math operation every time someone changed a CFrame, you would enjoy a lovely slow-motion game most of the time. [/quote]

Slow-motion games can be cool though :wink:

[size=2]However, that should be its own thread.[/size]