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Separate material parameter for reflection strength


#1

a separate material parameter for reflection strength would be great, this way it would be possible to limit the strength of the reflection whilst still maintaining the same level of roughness.

Additionally it would be great if the roughhness amount could be more linear. At the moment it seems to be 0 = mirror like, and then anything with a roughness value between 0.01 and 1 appears to be a similar level of roughness.


#2

I’m guessing this is related your other forum post: Different sky for reflections . Normally roughness values between 0.01 and 1 result in different level of roughness, but for uniform surroundings, such as a white sky texture, this different level of roughness will look the same. The surrounding captured in light probes is blurred with different levels of blurriness, the rougher surfaces use the most blurred levels, the smother surfaces less blurred levels. If the surrounding is uniform, all these blur levels will look the same (white in your case).

As for the reflection strength, we consider taking sky strength into account when calculating reflections. For now the sky strength is used only for baking (it is constant for reflections). The sky strength should allow to limit the reflection and is a physically based parameter. I’m not sure if reflection strength has physical interpretation. UPDATE: I forgot that you can already control reflection sky strength if you use HDR sky image in HDR formats (.exr, .hdr), in such case strength from the format is used.


#3

I didn’t know that Shapespark supports HDR-files. Will they still be a HDR file after packing the scene? I just wonder because usually these files are quite big.


#4

Shapespark supports HDR skies since July 2018. We didn’t advertise it, because it is just a partial support and the benefits are not yet worth the extra size.

The HDR skies are encoded in 4 channel PNG using RGBM encoding, so the result is much smaller than the original .hrd or .exr files, but much larger than LDR sky textures. The sky is used only during runtime, so you only see a difference for reflections, it is not yet used for baking.

A full support would require some strength multiplication parameter that would allow to tune the sky. Now some of the HDR skies that we tested are too dim, some too bright and the only way to tune them is to edit a texture in an external program. You can also change the camera exposure, but exposure affects the whole scene, so usually it is not a good option.


#5

Okay @jan. Thank you for this detailed explanation.