Lights not rendering with some materials

[benny_p]

I've just started learning to use Twilight Render 2 (hobby) with Sketchup Pro 2020 and encountered a behaviour I can't explain.

I have made a basic test scene with a cube and place one spotlight away from the cube a short distance. The light renders beautifully with any sketchup texture or colour applied, and even works fine with SOME textures in Twilight Render, but if I select certain materials in the template material window, the light doesn't render at all and the cube is dark.

E.g.

Plastic - Shiny - Renders fine
Wood - Flat - Fine
Metal - Aluminium - Totally dark
Metal - Silver - Totally dark
Glass - Common - Totally dark
Tile - Gloss - Fine

To be clear, if I enable the sun, faces lit by sunlight render fine, but it's my spotlight that doesn't work. There is no intersecting geometry - I've made sure of that.

Any idea why this might be happening?

[Fletch]

Hi Benny,
Please share link to test file here, we will test. Thank you.

[benny_p]

Thanks Fletch. You can find my SKP file here - https://www.dropbox.com/s/lfm7qyko5dc9e ... t.skp?dl=0

[Fletch]

Your spot light is pointing upward, and those materials are not "rough" on their surface, so that they are not reflecting any of that light back to the camera. So it appears that the light is not working, but it's working. I've added two more spots by copying your spot to make "extra sure".

That said, we recently modified the Easy 1-7 settings, and therefore there may be some adjustments that we need to make to improve their sampling. The aluminum material, for example, does seem darker than it should be.

Thank you for the question, we will look into it further.

[benny_p]

Thanks a bunch for your help with this, Fletch

[Chris]

As Fletch mentioned, we recently modified the render presets to disable features that were unnecessary in order to improve render speed. In so doing, the rendering of specularities was inadvertently disabled. We will update that in the next release to fix that issue.

In the meantime, if you have specular metals that (like aluminum) that aren't rendering, you can use the Tech -> Caustic settings which should render correctly (though a little slower, probably).

[benny_p]

Thanks Chris - I'll give that a try.