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I have a simple scene of the interior of a house (less roof). It does not in any way need to look realistic, just to be geometrically correct, therefore the walls and furnishings and fittings are simply constructed from primitive objects - cubes and cylinders etc.

The layout is fine, the problem is the lighting - very black shadows. The scene has the standard single directional light source.

What I need to do is provide overall diffuse lighting - equivalent to an overcast day.

I should point out that I am pretty much a novice on all this - lighting, shaders etc, though I have been reading a lot.

From what I read it appears that this is controlled by shaders, shaders being attached to materials, materials being applied to the objects. However, it doesn't seem to make much sense to me. Surely, a shader, if part of the object by virtue of being attached to the material, can only deal with how light might be reflected off the surface - but the light has to get there first.

Therefore, there must be a way of providing an overall diffuse light in the first place?

Or have I got this completely wrong? How does one get rid of the blackness on the non-illuminated side of an object? So far the only way I have found is to make the surface emit light, ie glow a bit, which surely must not be right.

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  • I thing you are looking for Ambient light. See also Fog and Ambient. There are plenty of resources online if you search for ambient light. Commented Jul 3, 2020 at 11:25
  • Sounds like it, thanks. Commented Jul 4, 2020 at 14:18
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    Ambient light is a way to fake indirect lighting and it's just overall diffuse lighting . You can read the Lighting section in Unity's manual for other ways of getting more realistic indirect lighting. Commented Jul 4, 2020 at 17:39

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Your general understanding of how this all works is correct. One way to look at it object request rendering, looks up the material, the material binds shader to a set of parameters. The shader then gets executed, once per light in the scene that affects it (this is simplyfying things but we'll get to that in a bit). This is why lights are expensive (in forward rendering that is), until optimizations start to kick in, this means rendering the scene n times.

So yes, you could just add a constatnt factor in the shader, to achieve the effect of 'ambient' or 'diffuse' lighting. But that shader, in order to support all the features like reflectivity etc, would have to be crazy complicated.

Fortunately, with unity we also get a middle layer called Standard Shader, which does pretty much all of the math underneath, and releases you from the necessity for writing shader code.

For a gentle, diffused look, you definitely want to look at baked Indirect Illumination features of Unity, maybe even lit everything with area lights only.

Its probably also a good idea to looki into light probe groups. They work with spherical harmonics, encoding only the low frequency components of the lighting data, effectively only using slow changing factors like general direction of the light.

unity docs for light group

Finaly look into reflection probes (and skyboxes while at it), theres few good free HDR probes available that will emit light into your scene (when baking lightmaps and baking lightprobes), enabling surprising realism, compared to default unity skybox.

If you don't want harsh directional light, just disable it (although it's often useful to know what is your strongest light source in your sene - even if its a skybox with some clouds, i would probably keep a scene light just to know faster if anything goes wrong

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Thanks, that is all very useful.

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