Did Blender lighting defaults change? Renders have hard shadows now

[matthijskooijman]

I'm looking to set up a blender render of my PCB (since the default render_3d is marked as deprecated and produced over-exposed results for me). However, my first attempts are a running into issues with the lighting, producing results that I do not appreciate.

Rendering my PCB with the default blender_export render (all options default), I get:

This is a reasonable render, except that the component shadows are quite prominent and IMHO counterproductive.

If I rotate the POV a bit (rotate_x: 30; rotate_z: -20), the shadow issue remains, and also the PCB seems somewhat over-exposed (especially in the lower left corner).

Since I wondered if this is intended, or what settings would be needed to produce more satisfying renders, I looked around and found: https://github.com/set-soft/kibot_3d_models_cache_example This example contains a render in its README:

This looks like a nice render - it is evenly lighted with only very subtle shadow that are not in the way. However, it is rendered with the default settings as well. But if I re-run KiCad with that example project and settings, I get:

Ignoring the difference in color, this shows that the current kicad code also shows (even more pronounced) shadows in this example, while the render in the README suggests that it did not use to, which leads me to believe something changed in the default rendering settings?

Anyone have any guidance about 1) what changed, and/or 2) what good settings are to produce clean images?

I tried fiddling around with the lighting settings and found that switching to SUN removes the shadows, but also produces a glare, making silkscreen unreadable in the center, or (with lower energy) too dark at the edge.

For example, rendering with:

    light:
      type: SUN
      energy: 1.5

Produces:

[matthijskooijman]

I had a bit of a look at Blender itself (but I have not experience with it, so totally unsure where to look) and noticed that a light source has a "Cast Shadows" checkbox. I did not manage to apply that, since rendering in Blendering failed with some error I did not understand. I also tried setting this option in the JSON generated by kibot and passed to blender --scene, but I could not find any documentation on the file format for this scene JSON file, so I just guessed some keys:

  "lights": [
    {
      [... more fields snipped ...]
      "shadow": false,
      "shadows": false,
      "cast_shadow": false,
      "cast_shadows": false,
      "no_shadow": true,
      "no_shadows": true,
      "type": "POINT"
    }
  ],

But that did not seem to change anything.

[set-soft]

I could not find any documentation on the file format for this scene JSON file

This file is just internal, used by the blender_export.py script (kibot/blender_scripts). I don't recommend messing with it, the format might change.

[matthijskooijman]

I did a bit more experimenting and found that setting transparent_background: true causes the shadows to become really black and hard. Compare the first image in my original post, generated with default images, with the below image generated with just setting transparent_background: true:

This render has very dark shadows (but OTOH I also do like the colortone or contrast of the rendering, better than the default rendering output).

Looking in the kibot source, I see that the transparent_background kibot option just sets the same-named option in the scene JSON, without any other effects, making this particular issue ( transparent_background causes dark shadows) a blender issue. However, I could not find any other mentions about this particular issue (mostly saw things about shadows cast by transparent objects, or shadows cast on a transparent surface/background).

[set-soft]

making this particular issue ( transparent_background causes dark shadows) a blender issue.

Is not an issue, is just how Blender works. When we set film_transparent to True no light is reflected by the background and shadows are deeper.

[set-soft]

There is no magic recipe for lighting, what works perfect for a board might not work for other. What looks perfect to a user might look ugly to other.

So you should play with the type of light, intensity and position. Even with this you might not find a perfect setup and then you'll need to manually adjust things from inside Blender.

Also note that light option supports multiple lights, the KiCad internal render uses various lights (and you get tons of shadows, but not so deep because some light from other angle makes it less important).

Looking a perfect result needs time and experimentation.

KiBot adds just one light at a position computed using an heuristic.