For those who have seen the sneak preview of the Nature Academy, a tutorial called “Create Realistic Snowy Mountains”, I’d like to critique the resulting render a little bit. For that you know what I’m talking about, please have a look at week eight (“Mountains”). I want to let you know how fog and mountains perform together in reality, because I’m looking forward to more realistic scenes as I’m not an artist.
First thing to know is that fog is near the ground. In case it is up in the sky, fog is called “clouds” . Maybe you have ever looked up into the sky vertically when it was foggy and you noticed that the sky is actually blue. At the same time you might have seen almost nothing when looking horizontally in front of you (due to the fog).
Let me show an example of a picture taken in Munich, Germany. Munich is near the Alpes, which have quite that type of mountains Andrew is creating in his tutorial. And from that photo you’ll definitely recognize that there is more fog at the bottom of the mountains than at the top. And of course there is less fog for near things like the houses – for near things close to the ground the Z buffer can be used as is.
Back to Andrew’s tutorial, he’s basically using the compositor and the Z buffer to create dust or fog. For those who downloaded the video and still have it, it’s at position 1:01:21. Actually he announced to add atmospheric glow (at 0:59:44), but anyway…
Using the Z buffer in an unmodified way means that there will be the more fog the further away things are. It does not consider the fact that looking more into the sky reduces the amount of fog. Therefore I recommend change the Z buffer before turning it into fog.
How can we achieve this in Blender? Obviously the problem comes from the compositor, so we’ll also fix it there. But first, we need an additional input for the fade out and it’ll be a texture. The texture settings are:
- Type: Blend
- Blend: Vertical
- Check Ramp
- Use white at the left
- Use black at whatever position matches your scene best
- Select Ease
With this texture set up, we’ll modify the Z buffer in the compositor like in the screenshot below. In order to highlight where the fog will be in the final render, I used red fog color here. The nodes are from left to right:
- Render Layer (always needed)
- Map Value (always needed for Z buffer to create fog)
- new: Texture (an input node, select the just created texture)
- new: Multiply (a color mix node)
- Mix (always needed to mix the fog into the scene)
- Composite or Viewer node at the end
Thank you for reading. Please share your opinions using the comment function.