Problems with instantiating baked prefabs

I had that same issue where the demo project would display in black in white. I noticed this was fixed if you open the BakeLightmapPrefabs scene and then run Bake PrefabLightmaps again

 

I'm in the same spot.

My procedure is the same as Racsoh in #311.

However I'm instantiating the prefab tiles on awake, then starting PrefabLightData.cs's Awake function after the prefabs are instantiated.

The result is black or just black and white.

I've tried this with several versions of Unity, including 2017.2.0f3 and 5.6.3.



Update :
'Update Scene with Lightmap Prefabs' from the above script results in...

Update 2 :
I was able to get this working, by using 'PrefabLightMap_with_editor_utilities.unitypackage' from a previous poster.

 

So is this working yet?

 

Depends on what you're talking about. Yes, you can bake lightmaps, assign them to prefabs and deliver them out via assetbundles (via the workaround and scripts mentioned in this thread). Is lightmap baking working correctly? Maybe not. At least not in all cases and surely not in all Unity versions.

 

I'm on 2017.1 and unfortunately I can't save Lightmapping to prefab levels which is a real pain. Even with the script I lose my lighting :-(

 

UPDATE: So the script is working, but light probes are not saved with the prefab scene. I opened the original scene where it is being built, and in the standalone build using UFE, the light map is "there" but the probes are not even calculated. I am also using Mixed Lighting, so that might be an issue.

 

Here is a shot from my test level with the light probes enabled so you can see what I am talking about. I turned on Light Probe Visualisation



And there is the same shot only running in UFE. The lightmaps saved, but there are no light probes saved AT ALL. And I am using Mixed Lighting. I also notice that my settings are overridden for this level too... the light is set to MIXED, but when I run my game, there is no way to set up the rendered like in the original scene.

 

So in further tests, the builds are loading my lightmaps, which I've tested rigorously for all of my levels... the only thing missing is preserving the light probes which show up in my normal scenes but not in standalone builds, especially in scenes with characters and dynamic objects.

 

UPDATE: So I have updated to Unity 2017.2 and the script appears to be working with the Progressive Lightmapper (quite well in fact) it's still white but I am not going to complain about it. Is there a way to get the light probes saved to this as well. It is strange that this is the only omission to an otherwise working script.

 

Were in the code could i change it to use progressive lightmapper?

 

I'm using the script stock. I learnt that it works with the PL by accident, and it looks SO DAMN GOOD! The only thing left is finding a way to get the light probe data to stick with it.

Whoever created the script can hopefully shed some light on this

 

I am using the same script posted by joachim Ante in unity 2017.2.0f2 and still cant save lightmap on terrains in a prefab. All other objects with mesh renderers are ok. just no lightmap on terrain for instantiated prefab. Terrain looks fine in the scene where i baked light but not in the instatiated prefab though.
I know its an old thread but still hoping agains hope. Any help ?

 

Hi all,

It doesn't work in 2017.3..

 

How do I prevent my baked prefabs from being lit twice? In the scene that I am instantiating the prefabs in, I would like to have a light that makes the prefabs cast shadows, but not brighten them any more. Is this possible?

I'm using Unity 5.6.

Thanks

 

I was having some problems with 2017.3.
It was creating a lightmap with xxx_comp_dir.png when the code was expecting a .exr file type.

Perhaps there's a way to get the light mapper to create .exr file but the solutiuon below worked for me.

I changed the line at 223 in PrefabLightmapData.cs to check for .png instead.

Code (CSharp):

1. lightmap_Remap.lightmap2 = GetLightmapAsset(filename + "_comp_dir.png", resourcePath + "_dir", originalLightmapIndex, lightmap2);

 

Can anyone help with my double lighting issue above? It feels like it must be a common problem with an easy fix. Thanks

 

I ended up hacking together couple of shaders to get the effect I wanted.

Code (CSharp):

1. // Unity built-in shader source. Copyright (c) 2016 Unity Technologies. MIT license (see license.txt)
2.  
3. // Unlit shader. Simplest possible textured shader.
4. // - SUPPORTS lightmap
5. // - no lighting
6. // - no per-material color
7.  
8. Shader "Mobile/Unlit (Supports Lightmap and Shadows)" {
9. Properties {
10.     _MainTex ("Base (RGB)", 2D) = "white" {}
11. }
12.  
13. SubShader {
14.     Tags { "RenderType"="Opaque" }
15.     LOD 100
16.    
17.     // Non-lightmapped
18.     Pass {
19.         Tags { "LightMode" = "Vertex" }
20.         Lighting Off
21.         SetTexture [_MainTex] {
22.             constantColor (1,1,1,1)
23.             combine texture, constant // UNITY_OPAQUE_ALPHA_FFP
24.         }
25.     }
26.    
27.     // Lightmapped, encoded as dLDR
28.     Pass {
29.         Tags { "LightMode" = "VertexLM" }
30.  
31.         Lighting Off
32.         BindChannels {
33.             Bind "Vertex", vertex
34.             Bind "texcoord1", texcoord0 // lightmap uses 2nd uv
35.             Bind "texcoord", texcoord1 // main uses 1st uv
36.         }
37.        
38.         SetTexture [unity_Lightmap] {
39.             matrix [unity_LightmapMatrix]
40.             combine texture
41.         }
42.         SetTexture [_MainTex] {
43.             constantColor (1,1,1,1)
44.             combine texture * previous DOUBLE, constant // UNITY_OPAQUE_ALPHA_FFP
45.         }
46.     }
47.    
48.         // Pass to render object as a shadow caster
49.         Pass
50.         {
51.             Name "ShadowCaster"
52.             Tags { "LightMode" = "ShadowCaster" }
53.            
54.             Fog {Mode Off}
55.             ZWrite On ZTest LEqual Cull Off
56.             Offset 1, 1
57.    
58.             CGPROGRAM
59.             #pragma vertex vert
60.             #pragma fragment frag
61.             #pragma multi_compile_shadowcaster
62.             #pragma fragmentoption ARB_precision_hint_fastest
63.             #include "UnityCG.cginc"
64.    
65.             struct v2f {
66.                 V2F_SHADOW_CASTER;
67.             };
68.    
69.             v2f vert( appdata_base v )
70.             {
71.                 v2f o;
72.                 TRANSFER_SHADOW_CASTER(o)
73.                 return o;
74.             }
75.    
76.             float4 frag( v2f i ) : COLOR
77.             {
78.                 SHADOW_CASTER_FRAGMENT(i)
79.             }
80.             ENDCG
81.         }
82.    
83.     // Lightmapped, encoded as RGBM
84.     Pass {
85.         Tags { "LIGHTMODE"="VertexLMRGBM" "RenderType"="Opaque" }
86.         CGPROGRAM
87.         #pragma vertex vert
88.         #pragma fragment frag
89.         #pragma target 2.0
90.         #include "UnityCG.cginc"
91.         #pragma multi_compile_fog
92.         #define USING_FOG (defined(FOG_LINEAR) || defined(FOG_EXP) || defined(FOG_EXP2))
93.  
94.             // uniforms
95.             float4 _MainTex_ST;
96.  
97.             // vertex shader input data
98.             struct appdata
99.             {
100.                 float3 pos : POSITION;
101.                 float3 uv1 : TEXCOORD1;
102.                 float3 uv0 : TEXCOORD0;
103.                 UNITY_VERTEX_INPUT_INSTANCE_ID
104.             };
105.  
106.             // vertex-to-fragment interpolators
107.             struct v2f
108.             {
109.                 fixed4 color : COLOR0;
110.                 float2 uv0 : TEXCOORD0;
111.                 float2 uv1 : TEXCOORD1;
112.             #if USING_FOG
113.                 fixed fog : TEXCOORD2;
114.             #endif
115.                 float4 pos : SV_POSITION;
116.                 UNITY_VERTEX_OUTPUT_STEREO
117.             };
118.  
119.             // vertex shader
120.             v2f vert(appdata IN)
121.             {
122.                 v2f o;
123.                 UNITY_SETUP_INSTANCE_ID(IN);
124.                 UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
125.                 half4 color = half4(0, 0, 0, 1.1);
126.                 float3 eyePos = UnityObjectToViewPos(float4(IN.pos, 1));
127.                 half3 viewDir = 0.0;
128.                 o.color = saturate(color);
129.                 // compute texture coordinates
130.                 o.uv0 = IN.uv1.xy * unity_LightmapST.xy + unity_LightmapST.zw;
131.                 o.uv1 = IN.uv0.xy * _MainTex_ST.xy + _MainTex_ST.zw;
132.                 // fog
133.             #if USING_FOG
134.                     float fogCoord = length(eyePos.xyz);  // radial fog distance
135.                     UNITY_CALC_FOG_FACTOR_RAW(fogCoord);
136.                     o.fog = saturate(unityFogFactor);
137.             #endif
138.                 // transform position
139.                 o.pos = UnityObjectToClipPos(IN.pos);
140.                 return o;
141.             }
142.  
143.             // textures
144.             sampler2D _MainTex;
145.  
146.             // fragment shader
147.             fixed4 frag(v2f IN) : SV_Target
148.             {
149.                 fixed4 col, tex;
150.  
151.                 // Fetch lightmap
152.                 half4 bakedColorTex = UNITY_SAMPLE_TEX2D(unity_Lightmap, IN.uv0.xy);
153.                 col.rgb = DecodeLightmap(bakedColorTex);
154.  
155.                 // Fetch color texture
156.                 tex = tex2D(_MainTex, IN.uv1.xy);
157.                 col.rgb = tex.rgb * col.rgb;
158.                 col.a = 1;
159.        
160.                 // fog
161.             #if USING_FOG
162.                 col.rgb = lerp(unity_FogColor.rgb, col.rgb, IN.fog);
163.             #endif
164.                 return col;
165.             }
166.  
167.         ENDCG
168.     }
169. }
170. }
171.  
172.  
173.  
174.  

 

Hi All,
I have a scene with 4 prefabs with the lightmapdata script added baked the light , now the scene has total 3 2048x2048 lightmaps, everything looks fine. The problem is when I reload the prefabs in gameplay the Scene lighting show 48 2048x2048 lightmaps loaded. I mean shouldn't it use the same loaded lightmaps for the scene for the optimal performance rather that loading the same lightmaps again and again for each prefab ? 12 times to be precise. The lighmap size jumps from 8.0MB to 128MB I am a mobile game developer something doesn't seem right.

Second thing when I reload the same scene for a restart of the game lightmaps wont load untill after 4-5 tries maybe those number of lightmaps take some time to load I dont know for sure yet.

any help will be greatly appreciated as I am on the verge of completing this long project.

 

Thank you so much it solved my huge problem. Best Regards

 

Finally got this working for me in Unity 2017.2. Works fine with ProBuilder objects and the Progressive lightmapper.

Using the Editor script from this post: https://forum.unity.com/threads/problems-with-instantiating-baked-prefabs.324514/page-5#post-2519284

Importantly, I had to make a change to PrefabLightmapData.cs
on line 222 where the script hard codes the comp_dir lightmap file:

Code (CSharp):

1. lightmap_Remap.lightmap2 = GetLightmapAsset(filename + "_comp_dir.exr", resourcePath + "_dir", originalLightmapIndex, lightmap2);

I changed the extension to png as my bake wasn't generating a file ending in "_comp_dir.exr" but a png instead:

Code (CSharp):

1. lightmap_Remap.lightmap2 = GetLightmapAsset(filename + "_comp_dir.png", resourcePath + "_dir", originalLightmapIndex, lightmap2);

This has become a bit of a monolithic thread with a lot of different advice. After making the above code change, what worked for me was
1. turning off batching static, adding the PrefabLightmapData component on the parent of the prefab and
2. baking using the Editor utility linked to above (Window > Prefabbed Lightmap).
After clicking on Step 1 bake, you sometimes get a duplicate of the PrefabLightmapData component. Just remove it.
3. I found I had to disable the lights on the prefab otherwise they still appeared in the destination scene (even though they were set to baked).
4.Then finally apply changes to the prefab.
5. In the destination scene, add a cube or something and bake a very basic lighmap. For some reason it's needed for the prefab lightmaps to work properly.

 

Also works in Unity 2018.1.0b13.
A very helpful script.

 

So how does this work exactly?

I have about 20 room prefabs I instantiate at runtime so baked lighting is out, does this allow me to store the lightmaps and at runtime 'bake' each instantiated room (there might be duplicates)? Taking into account the rooms could be positioned anywhere and rotated 0, 90, 270, or 360 degrees

 

No, the point of this is that you bake your lightmap into the prefab. The only thing that happens at runtime is that you instantiate the prefabs. The baking is not done at runtime so it won't take into account rotation. You could, I guess, have different versions of each room (for each rotation). It is tricky to minimise the visible seams caused by lighting changes from room to room. The 'construction' process needs some thought, with identical lighting for all rooms, or at least at their joins.

 

As long as you dont bake a directional light you should be fine.
I had a similar setup where the prefabs (rooms in my case) could be rotated at 90 degree intervals.
All rooms were lit with either spot or point lights and baked per prefab. In my case I joined the rooms so to get a smooth transition I added the same light above the joining point to all prefabs.

 

did anyone get Light Probes to work on prefabs?

 

I can't seem to get this working for the life of me, and without light probes it seems pretty much useless. How has it been 3 years without a Unity dev response in here? This isn't exactly an obscure niche feature request, it's practically needed for procedural generation, especially if you're going with VR. (Yeah. I'm salty.)

 

Hello guys! I have a problem when building project to device iOS it seems like it cant convert or compress exr texture to propper format to PVRTC_RGB4. Please help to solve this problem, because in Unity it works but on a device no.

 

Does this script use the lighting window for getting its settings? It does not seem to respect it (such as increasing lightmap resolution via texel size does nothing to the final bake but it does if I use the direct baking window).

Id really like to be able to use this workflow but control the bake. RIght now shadows are too weak and without most of settings in lighting window it is hard to change that

 

@jeromeWork @pcg @Diego_Graphics @Joachim_Ante does this work with the LWRP?

 

Now that's a good question! I've not tried it but would be interested to know too. I've personally not made it to 2018 quite yet.

 

I was using LWRP and baking prefabs so yes it works up to a point.
Where I had to abandon this is I could not get light probes to work as i wanted.
I wanted to bake light probes per prefab and then spawn the prefabs and magically use the associated light probe group.
In hindsight it was naive of me to think this would work once I looked further in to light probes etc.
I'm still seeking a suitable solution do to what I want which is semi procedural 3d environment from prefabs with baked probes.

EDIT: Actually I may not of been using LWRP at the time. I switched to additive scenes and LWRP at about the same time so TBH I'm not entirely sure. Sorry.

 

Okay thankyou for the fast response! Can anyone else here shed any light? @Joachim_Ante posted the original post so hoping he will chime in?

 

@pcg For semi procedural 3d environment from prefabs, you may want to keep an eye out for @AdamGoodrich 's upcoming Origami (https://discord.gg/HavN5J5) Sounds as if it will do exactly that kind of thing.

 

I also got it to work in 2018.2 ,
I did have to rename _dir.exr image to _dir.png, apparently thats what unity call that specific light map now.
png reference:
https://forum.unity.com/threads/problems-with-instantiating-baked-prefabs.324514/page-8#post-3458376

The editor script i got from here:
https://forum.unity.com/threads/problems-with-instantiating-baked-prefabs.324514/page-5#post-2519284

I just use non-directional because in the past i had issues rotating objects at runtime with directional. i lose some normal map effect but its minor compared to being able to rotate properly.

i highly recommend giving it a try with directional lightmaps as well, if you arent planning to rotate objects, it does appear to have proper support for directional lightmaps. and it looks really good when spawning a run time. But if you rotate objects at run time, then defintely non-directional in both the bake scene and the runtime destination scene.

One issue i think is that it appears to be designed to only support 1 bake scene because you select the directory and it over writes the images.

Thats unfortunate, if you have multiple bake scenes so that you can divide your objects up, thats the best because then the prefab can just point to that scenes lightmaps.

Its a step backwards for that. I may have to modify it because some objects are quite large and any time i add an object i shouldnt need to rebake all of my old objects, specifically if they take up about 1024x1024 or higher each lightmap.

Great job to everyone for contributing to improving it, i dont know why unity hasnt implemented this by default yet. i also think it might be helpful to have 2 separate arrays to make it faster to drag renderers into the array list. But thats minor in the grand scheme of things, couldnt take more than 1-2 seconds each time you want to modify/add/remove a renderer.

*EDIT*
I just realized, if you choose a different scene, you can atleast manually type in a different target lightmap directory.

 

Oddly im having an issue where at runtime my objects end up black, i think it might have something to do with the lightmaps being moved incorrectly, i am not sure yet, anyone had this before? i dont have static batching on or anything, i even disabled it in the script itself.

 

it was working in 2018.1.0f2, after upgrading to 2018.2.2, baked lightmaps no longer appear in my prefab folder

 

i cannot get the plugin to bake into my prefab folder on 2018.2.2

 

So i solved the issue, in 2018.2. you have to include the bake scene with your main project. thats regardless of the platform target. The script given was originally supposed to target a Resources folder so that it could include any missing files, unfortunately it appears that only moves the texture/asset but not the original light data asset that is in the scene itself. i am not sure why its being referenced still.

But including the bake scene will make your lightmapped prefabs show correctly at run time

 

hello everybody, I've load lightmap serveral months ago.and my new problem is that the light is quite dark than the orginal.
this is original:


this is loaded :



by the way, I found the value of m_Lightmaps2 is always to be empty,so I changed the line 73 to
"
newLightmapData.lightmapDir = lightmaps;
"
otherwise, the scene will be like this:




I don't know what's wrong with it,any help will be appreciated.

 

Hello,

I wasted hours to figure out how to make it work, but it’s working fine now on PC and Android builds with Unity 2018.1, so I thought I should share my process:

- Create an empty scene called “BakeLight”
- Add point lights, set “Baked” mode
- Add all the prefabs to be baked in the scene
- Add in the Parent of all the prefabs the “PrefabLightmapData.sc” script from Joachim_Ante:
https://forum.unity.com/attachments/lightmapinprefab-zip.146782/
- Set MeshRenderer of the prefabs:
“Lightmap Static” ON
“Scale in Lightmap”: 0.1 (to have hundreds of 3d objets lightmap to fit in one texture. Otherwise, by default it will generate 1 lightmap per object, which is huge and not performant)

- Open “Windows” – “Lighting” and do this setup:
"Auto Generate" OFF (near button “Generate Lighting”)
“Realtime GI” OFF
“Lightmapper” Progressive
“Bounces” 1 (faster for rendering, but a bit less precise)
“Lightmap Size” 1024 (a good compromise for mobile)
Then press “Generate Lighting”

- Then use the tool from Joachim_Ante :“Assets” – “Bake prefab lightmaps”
- Check in the game objects of the scene that the component PrefabLightmapData was not duplicated in the process (it happens). If so, just delete one of the 2 components.
- “Apply” the modifications of all the game objects (GO) and save the scene

Then, to use the created GO with lightmaps, this is where it was tricky to figure out. In my case, I use a totally empty Scene to instantiate the GO. If so, this is what you need to do:
- If your target scene is empty, add a 3d cube or anything in 3d
- Open the Lighting window
- Use EXACTLY the same Lighting parameters as for the “BakeLight” scene
- Generate the lightmap of this scene by pressing “Generate Lighting”
- You can then delete the 3d cube as it was just needed to generate the texture

=> You should be all set to instantiate GO with lightmaps in it.

THE TRAPS:

=> If you don’t generate at least once the lightmaps in your target scene, you will have dark lightmap in the Editor playback, because you need the LightingData file to be generated (in your “Scene” subfolder)

=> If your target scene is empty when you generated the lightmaps, it won’t generate the Lightmap-0_comp_light file (in your “Scene” subfolder), and the lightmap will work in the Editor, but will be dark in the Android or PC build (it took me a verrry long time to figure out this step)

Hope this is helpful and will avoid hours of try-and-error for the next one arriving on this thread…

 

That's an awesome post man, really useful.
I have one issue that doesn't seem to be described before though: as soon as I add lightingdata to my scene I can't build the project anymore, I don't get any specific errors, it just stops at sharedassets3 file.
Any ideas?

EDIT: Ok, I had to remove 3 game objects from my scene and recreate them exactly the same for some reason, but the build works now. Except I still have black maps when I build to android, even though I have the Lightmap-0_comp_light file (it's all black though).

 

For your black screen on Android build, it can be many problems... It can be the lightmap texture format that is not compatible with the Android device, or it can be the texture that is not included in the assets list in your Android build, or it can be that the script didn't generate the correct infos for each GO, or else...
I would advise that you start eliminating problems:
- Switch platform to PC, play with Unity player : All black = maybe a problem with the script. Check the Component "PrefabLightmapData" in the GO and see if Lightmaps point to readable textures. Check a few Elements a see if they point to the lightmaps and have correct coordinates.
- If it's working on Unity player PC, try to make a Build PC : All black = maybe a problem with the lightmap texture not being loaded in the list of the assets of the build. You can add this piece of code in the PrefabLightmapData.cs:

void OnGUI()
{
GUI.DrawTexture( new Rect( 0, 0, 256, 256 ), m_Lightmaps[ 0 ] );
}
It should display the loaded lightmap texture on screen (it's really dirty, but it's an easy way to check if the texture is properly loaded). If not, if you are using a assetholder or else, maybe you need to add the lightmap in the list of assets to be included in the build... or it could be the problem with the Lightmap-0_comp_light default file that was not created with your empty scene, or else...
- If it's working in a PC Build, switch platform to Android and try in Unity player: All black = probably a problem with the lightmap file format. Test with the piece of code to display the texture.
- If it's working on Android Unity player but not on Android build, then I have no idea sorry.

 

Thanks @Davideogames! I really appreciate the time you took to write this!
I tried some of the things you mentioned and the OnGUI method shows my texture on the screen on Android. All the prefabs are still black though.
I did find another lead, it looks like for some reason the lightmaps don't work at all in my Android build, even without the prefab script. So that's what I'll investigate now.

EDIT:
Ok, once I figured out the lightmaps don't work at all it was relatively easy to find the solution.
I just had to go to Edit -> Project Settings -> Graphics -> Shader Stripping -> Lightmap Modes and enable "Baked non-directional".
Thanks again for your help!

 

I noticed a lot of people ask about light probes but no one r”ever responded... is it possible to include light probes in prefabs? If it is I can’t figure it out but I don’t really see the point of lightmapped prefabs without lightprobes.

 

No I dont think its possible. The solution I have resorted to is as follows...

I have all the prefabs in a single scene with light probes in etc, and bake it. I then use the Prefab Lightmap tool from this thread to bake the lightmaps on to the prefabs.

My prefabs are rooms for my level and I have a trigger collider around the prefab so that when my character enters a new room I know which prefab he is in.
I create a level from the prefabs.
I have an empty game object which follows my character around but the position is translated to within the original prefab position in the scene in which it was baked. I use this empty game object as the Anchor override on my characters mesh renderer to solve the light probe problem.

Unity has recently released something on the asset store explaining how scene lighting works.
I've not looked at it yet so im not sure how helpful it will be but heres a link.

https://assetstore.unity.com/packages/templates/tutorials/additive-loading-lighting-examples-129922

 

Have we figured out how to get prefabs working with GI? I'm using the UFE asset and sadly with the way the asset is set up, precomputed lighting, baked lights, and reflection probes DON'T WORK with it!! I've mentioned this to the devs numerous times and no one will listen to me! It uses prefabs as levels and in order for me to save reflection probes, I have to set it to Custom...

And the last part is saving light probes...

 

I just wanted to chime in with a few things:
If you change the line that says

Code (CSharp):

1.  Lightmapping.Bake();

to

Code (CSharp):

1. Lightmapping.BakeAsync();

You'll get a Unity that doesn't lock up during baking, as well as a progress bar in the bottom right showing progress, as well as the ability to open the Lighting Settings window and Cancel a bake.

to compress lightmaps and reflection probes (uncompressed are huge!), I made a separate script:

Code (CSharp):

1. using UnityEngine;
2. using UnityEditor;
3.  
4. // Compress any texture in /Scenes/*, ie: lightmaps and reflection probes
5.  
6. class CrunchLightmaps : AssetPostprocessor
7. {
8.     void OnPreprocessTexture()
9.     {
10.         if (assetPath.Contains("Scenes"))
11.         {
12.             TextureImporter textureImporter = assetImporter as TextureImporter;
13.  
14.             textureImporter.textureCompression = TextureImporterCompression.CompressedHQ;
15.             textureImporter.crunchedCompression = true;
16.             textureImporter.compressionQuality = 100;
17.          
18.         }
19.     }
20. }

I'm an artist not a programmer so apologies for any fugliness to these solutions

 

Tested this in Unity 2018.3 - had black and white textures after the bake - solution:
Lightning - Lightmapper settings - Directional mode - non-directional

Other than that, thanks for that. Still doesn't look good at all, but at least it bakes

BakeAsync
Also somebody recommended UnityEditor.Lightmapping.BakeAsync(); to see the progress instead of UnityEditor.Lightmapping.Bake(); I spent two days finding out why my textures were misplaced all around incorrectly and it was because of this. So keep there Bake(). (BakeAsync worked for me only sometimes and only for one prefab, not with multiple in one bake scene)
Best is actually to comment out this line, bake manually and then run the script to assign the lightmaps.

 

Do the lights have to be points? Will directional lights work? The scene my prefabs are used in is outdoors, and has only directional lighting.

 

Same. Is there a way to get directional mode to work?