5.6.1 emissive materials behave differently than in 5.5

Development Asset Creation
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1

Hi, we’re seeing a strange change in the emissive brightness of our materials after upgrading to 5.6.1. This happens regardless of whether or not the material is lit or unlit.

Here’s an identical material opened in the stock launcher version of 5.5.4 and 5.6.1 respectively. I simply created a new material, set the emissive value to 0.5 and fixed the viewport EV so it was identical in both editors.

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Is this expected behavior?

2

Steps to Reproduce

  1. Create a material with an emissive value in 5.5.x
  2. Open that material in 5.6.x
3

Hello,

Thank you for reaching out.

I’ve been assigned this issue, and we will be looking into it for you.

4

Hello,

In the material editor, the difference is coming from the default property value. The behavior is only different when adjusting the default color assigned to the emissive value pin. If a constant expression is connected to the pin, the behavior is the same between UE 5.5 and UE 5.6.

There were changes to UE 5.6 related to HLSL translation, material designer, base and emissive channels. We will investigate further and get back to you.

Let us know if this helps.

5

Thanks for getting back to me. That’s interesting information. I can confirm that plugging in a constant value node results in the same color in both engine versions, which suggests this was a bug in previous engine versions that was fixed in 5.6. I would still appreciate knowing what changed though, since we will likely need to write some automation to fix up our old materials that relied on this incorrect behavior.

6

Hello,

Thank you for the reply.

Since this is change is a result of bug fixes and updates to the translator and rendering, we could not point you to a single change that might be helpful.

From more tests it looks like 5.6 does the correct thing that is, consistently renders the same way when using default value or a constant value. 5.5 had an inconsistency between the two ways of piping the value and that seems to have been fixed with the translation and rendering changes.

Let us know if this helps.

7

That’s unfortunate, sounds like we’ll just need to hand author updates to those material values that approximates the old (incorrect) look. Thanks.

8

Hello,

Thank you for the reply.

I will close this ticket for now. Please feel free to re-open the case if you have additional questions.