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One decision when making in a shaded relief, whether it’s done in Blender or elsewhere, concerns how much vertical exaggeration to apply to the terrain. The Earth is actually quite smooth, and so we have to make the mountains higher and the valleys lower than they really are if we want them to show up. Right now, I can see the terrain fairly well in my rendered relief, but what if I want to adjust it some?
To do this, we first need to select the plane, and then go back to the Node Editor. This is where we were telling Blender to apply our heightmap as a texture to the plane. We can change our exaggeration by first multiplying our texture by some constant factor. Choose Add → Converter → Math from the bottom menu bar.
Drag this new node over the line connecting the Image Texture and the Material Output. You’ll see the line highlight in orange. Place the node there, and you’ll see it automatically plugs itself in to the right spots.
From the dropdown menu that says Add, choose Multiply. This node now will take the heightmap image texture and then multiply it by some number, making the terrain higher or lower as a result. You can plug in whatever value you want here. Higher numbers mean a more exaggerated terrain. Play around with this and do some test renders. I’m going to go with 3.0.
Note that keeping the number at 1 doesn’t mean that there’s no vertical exaggeration. By the time you get your data into Blender, all spatial information has been lost to the ether, and it would be tough to calculate the relationship between the vertical and horizontal scales. That’s not usually of any concern to me, as I’m just eyeballing the exaggeration factor until it looks good.
Adjusting Render Settings
We’re closing in, but there are still some more things to adjust before we’re done. First, we need to go back to our Render Properties by again clicking on the still camera icon.
When last we were here, we looked at the render dimensions. Remember that you can change the percentage, just below the X and Y, to make smaller, faster renders while you test stuff out.
A little ways below that you’ll find the Sampling options (you might need to click to expand the options). Under Samples, you’ll see a setting called Render.
This controls the quality of the final rendered image. If I set it lower, the result is more grainy, but it also renders much faster. I usually keep this low (30 or so) when I’m doing test renders, and then I increase it to around 200–300 when I’m doing the final render.
Now, sending that render setting higher (and thus getting a smooth relief) means that generating your final image takes longer. Fortunately, starting in Blender 2.79, there’s another option: noise reduction. Instead of taking a long time to generate a smooth image, you can instead generate a quick grainy image, then apply noise reduction.
To turn on this option, you’ll need to go to the Render Layer Properties, which you find by clicking on the icon of a couple of photographs, just to the right of the still camera icon.
Once there, you can check the box for Denoising. You’ll also see a bunch of options for this setting. I am inexpert in which to use (this portion of the software is relatively new), so I leave their exploration as an exercise to you, gentle reader.
So, you now have two ways to get a smooth render: crank up your render samples really high, or keep things coarse and grainy, but then run noise reduction afterwards. The latter is faster. But, also note that it’s not a panacea. There’s a balance to be found between the amount of noise reduction and the amount of render samples. In the example below, notice that noise reduction on a coarse render leaves you with some artifacts. Increasing the number of samples, even while keeping noise reduction on, helps reduce those.
Alternatively, adjusting the noise reduction settings may help, as well. It’s an area worth exploring, and noise reduction gives you another tool to use in finding a balance between speed and quality. I’d suggest it would be particularly useful for doing test renders, when you’re trying to figure out lighting & vertical exaggeration on your relief. These are situations in which any artifacts don’t really matter, and in which you want to see results quickly. Once you’re set for your final render, you can still increase your render samples, and reduce or deactivate denoising (depending on how much time you have to let it generate).
Once you’ve had a look at denoising and turned it on (or not), let’s quick jump back to the Render Properties (the still camera icon). There’s one last thing to tweak here. Have a look at the Light Paths options. This is another quality vs. speed sort of setting, in this case related to how much effort Blender puts into calculating how light bounces around your scene. From the dropdown menu, select Limited Global Illumination. You may be tempted to choose Full Global Illumination instead, but it will take longer to render, and you will almost certainly not see any difference. For the sort of work we’re doing, Limited Global Illumination is just fine.
Saving the Relief
Now that all the settings are tweaked, we can do one final render that we’re happy with. So, go to the top menu and once again choose Render → Render Image.
Once your render is complete, go to the bottom menu and choose Image → Save as Image.
You’ll be taken to a file browser where you can choose its name and location. On the bottom left, under Save as Image, you can also choose your file type, bit depth, and color mode.
Once you’ve got those settings to your liking, you can hit Save as Image way up in the upper left, and then you’re done!
Repeating the Process
Now, that all probably took you a really long time, but there’s some good news: you’ll never need to do most of this stuff again. Go up to the top menu and choose File → Save — hopefully you’ve been doing this at intervals all along. Once you’ve got it saved, you can re-use it any time you like.
When it comes time to make a brand new relief, you just need to follow an abbreviated set of steps, since your studio is mostly set up already.
- Change the dimensions of the plane to match the aspect ratio of your new heightmap.
- Edit your output dimensions in Render Settings, so that the final image matches your new heightmap.
- Edit your camera’s Orthographic Scale to match your new plane dimensions.
- Go to the Nodes Editor and choose your new heightmap file.
You might also want to do some test renders while you tweak your vertical exaggeration (the Multiply node in the Nodes Editor) or maybe your lighting. Before doing that, you could speed up the process by shrinking your output image, and/or by lowering the number of render samples; put everything back to full strength when you’re happy.
So, despite how long your first relief took, your next one can be ready to go in minutes!
This tutorial is, and will remain, free, but if you derive some value from it, you are welcome to make a donation to support my continued work.
Next Chapter: Advanced Thoughts