Specials:

- Lightnings are randomly created. All the minimum and maximum values are here for a random range.

Note: Because the collection order is made automatically by the THUNDERSTORM add-on, the collections must not be disabled in the outliner, otherwise errors will occur.

Example: When a cloud is created, the cloud is set active. But this is not possible if the CLOUD collection is set inactive.

General:

So that you don't have to trudge through endless documentation, I'll simply describe the most important things I noticed during the creation of Thunderstorm Add-on.

In general, almost all parameters are provided with tooltips, which explain directly in Blender what the function is. Except for materials that are already present. Unfortunately, you can't enter tooltips for them yet, but the names of the functions are very clear and can be easily tested.

Transparency is used in all areas of Thunderstorm Add-on. This is not a problem in Eevee, but in Cycles transparency is unfortunately displayed in black if a too low number is set under Properties > Render > Light Paths > Max Bounces > Transparent. It is best to set the number very high, e.g. 512. The rendering does not take longer if a high number is set here.

Lightnings

Each flash can be treated individually. Both for editing, as well as for updating via the Update Lightning button.

The Lightning Emitter is responsible for many flashes at once. This is a plane that produces as many lightning bolts as you specify. If changes are made in the settings and you want to apply them to the lightning emitter, you can simply press Update Lightnings in the Emitter.

There are also settings that can be applied directly to the flashes. Go to the "Settings after Creation" tab, where you can directly change color and such.

Clouds

The new 2D clouds have the great advantage that they can be rendered very quickly, especially with Eevee, and look beautiful and detailed.

The clouds can also be mixed. The 2D Clouds for nice contours and the Volumetric Clouds so that the light behaves like in fog.

Rain

Rain effects are extremely light dependent. The best way to see rain is with environment maps in world shading. But even there are many different results. It's best to try several environment maps until you find one that shows the rain the way you like it.

The Rain Splashes are fully designed for performance.
It's best to let the splashes sprout on decoupled surfaces so that not everything is covered with them and then the scene is slowed down after all.

The somewhat more special sounding function "Normal Z Influence" specifies how much the normals can deviate upwards from the display in order to still be considered.

This is how it looks like:

And the exact same with the Rain Splashes:

If you have added rain splashes but they are not visible, the object's normals may be rotated. What is a bit confusing here is that the splashes do not appear on the bottom side, because normals facing away from the top should not generate splashes.

Compositing Node

I prefer to use 2 Thunderstorm compositing nodes. One to decide how strong the flash should shine before it is fully extended and one to decide how strong the flash should shine afterwards.

This can be easily done by editing "Threshold" and "Input Limit".

Important: always add the node via the menu:

Shift A > Filter > THUNDERSTORM.

This is important because drivers are added that will not work if you duplicate the node.

The Thunderstorm compositing node also works in realtime compositing.

Dive a little deeper into details:

Spline Settings >

Main Spline = blue

First Splines = green

Second Splines = red

Main Spline >

Thickness

The minimum and maximum thickness.

Close Tip

Close the tip of the main spline. Endpoint Thickness = 0.

Length Range

The minimum and maximum length.

Subdivisions

The number of points (curve points) in the main spline.

Noise Size

The noise strength of the Main Spline.

Bending

Maximum Bending

First Splines >

Chance For Splines

The chance for splines 1 to (smaller value is more likely to result in splines).

Amount Range

Minimum and maximum number of splines created if the attempt was successful.

Thickness

Minimum and maximum thickness of the first splines.

Use Main Spline Length

With this option, all first and second splines will have approximately the same length as the main spline. The point of this is that all splines extend together, as is the case with a real lightning bolt. (The splines will not be exactly the same length due to noise and bending).

Segment Range

A segment is the part between two points on the spline. Here you can set the minimum and maximum number of these segments per spline.

Segment Length

Minimum and maximum of the segment length.

Noise Range

The noise magnitude of the first splines (randomly between 0 and the specified magnitude).

Bending

Maximum Bending

Second Splines >

Chance For Splines

The chance for splines 1 to (smaller value is more likely to result in splines).

Amount Range

Minimum and maximum number of splines created if the attempt was successful.

Thickness

Minimum and maximum thickness of the second splines.

Use Main Spline Length

With this option, all first and second splines will have approximately the same length as the main spline. The point of this is that all splines extend together, as is the case with a real lightning bolt. (The splines will not be exactly the same length due to noise and bending).

Segment Range

A segment is the part between two points on the spline. Here you can set the minimum and maximum number of these segments per spline.

Segment Length

Minimum and maximum of the segment length.

Noise Range

The noise magnitude of the second splines (randomly between 0 and the specified magnitude).

Bending

Maximum Bending

Note: The length of the splines must not exceed the length of the main spline, otherwise the extension of the flash could look wrong. However, if the flash is not to be extended, it does not matter.

Lightning Settings After Creation >

These settings are common settings to change after the lightning is created.

Note: these settings are only available when a lightning is selected.
these options are very useful for single lightnings or baked lightnings for fine-tuning.

Compositing

To make the lightning bolts glow, enable Bloom in the Eevee engine in the render settings, or make them glow with the THUNDERSTORM node group in the Compositor. You can find this node group in the Filter section.

Note: for Cycles, all lightnings are assigned the material id 1001. However, in order to use this material ID, it is necessary to set the Alpha Threshold in the View Layer Properties to 0, because the lightnings are provided with an alpha channel.

Note: Unfortunately the Thunderstorm Node Group cannot be duplicated, because drivers regulate the Blur Size. The drivers will not work in the duplicated node.

If you want to have 2 or more Thunderstorm Node Groups, you can simply add them via Shift A > Filter > Thunderstorm.

Threshold

The threshold determines how much something must glow before the glow effect is added.

Input Limit

Maximum of the included strength.

Input Intensity

The brightness before the effect. If something in the image is not quite as bright as desired, this can be used to make it brighter.

Output Intensity

Makes the whole effect more intense.

Note: when the lightnings shine through clouds, they have different emission intensities.

Blur 1-4 Factor

This is the blur intensity and size of the four blur nodes within the Thunderstorm_NodeGroup.

Note: The Thunderstorm compositing nodes cannot be duplicated, because drivers are used to control the blur size.
So if you need more than 1 Thunderstorm node, for example to use different thresholds, you can simply add another node via the Filter menu.

Inside the Node Group:

Outliner Order:

THUNDERSTORM_COLLECTION

Everything that is created with the THUNDERSTORM Add-on is in
this collection.

__THUNDERSTORM_Planes

The Thunderstorm Planes are located here for easy reference when you want to access the Thunderstorm settings.

THUNDERSTORM

Every thunderstorm you create gets its own THUNDERSTORM
collection.

BAKED_LIGHTNINGS

Here are the baked lightnings.

THUNDERSTORM_Empty

Everything in the THUNDERSTORM collection is parented to this empty.

CLOUDS

All clouds are in here. When you make an object a cloud,

it will be linked here as well.

RAIN

The rain emitter, the particles and the force field are located here.

Render Helper:

For a good rendering of the lightnings and the clouds in Eevee, some settings still need to be made:

For glowing lightnings, enable Bloom in the Rendering section. The default settings are fine, but if you have other emissive materials in your scene, you should set the Threshold to a high value if you want to make only the lightnings glow.

If you are working with Cycles, don't forget to set Transparent high in the Light Path Settings. The flashes disappear via Transparency, which is displayed in black if the value here is not set high enough. Small parts in the flashes overlap. This can lead to black spots.

For beautiful clouds, there is no other way than to play around with the settings in the Volumetrics section of the Render Settings.
The most important of these:

Start, End

No clouds will be rendered or displayed in the viewport if they are outside the range you specify here. This is very simple, but can be confusing if you have spent most of your time working with cycles for which no such settings are available.

Tile Size

Smaller numbers show more details in the clouds, but it also needs
much more data memory.

Volumetric lightning

Must be activated for the light of the lightnings to interact with the clouds.

Note: in Eevee, emission materials are indirect lights and
must be baked. But baked materials are not animated.
To make the clouds interact with the lightnings, point lights must be added (they are added by default). This way, the light behavior in the clouds will look as you expect.

Volumetric Shadows

Should also be enabled for more complex looking clouds.

If you need more information about volumetric settings or anything else in the Blender UI, check out the Online Manual.

The easiest way to get there is to hover over the setting you want, press the right mouse button and then select Online Manual, as shown here in the image: