Blender Relief Tutorial: Final Adjustments

Previous Chapter: The Sun

Vertical Exaggeration

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 if you want to make adjustments, remember that you can select your plane, then head on over to the Shader Editor and adjust the Scale parameter on your Displacement node.

Earlier, I decided to go with 0.3, but feel free to play around with the number and see how it affects things. This is basically a multiplier that gets applied to the heightmap you feed into Blender. So, you may need to adjust this number a fair bit depending on the heightmap you are using. Experiment around and find something you like.

On the left, a Scale of 0.3, and on the right, a Scale of 0.6. The terrain looks taller, with darker shadows, in the latter.

I’d recommend a light hand with this parameter. You want the terrain to be strong enough to be perceptible, but not overly exaggerated. The more you exaggerate it, the darker the shadows can get, and that can potentially mean a loss of detail.

Note that keeping the Scale value 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 that grey camera icon. When last we were here, a long time ago, we set our rendering engine to Cycles. Right below that, you’ll find the Sampling options (you might need to click to expand the options). There, 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.

SmoothCoarse.jpg

A coarse render with 20 samples vs. a smooth one with 250 samples.

Now, sending that render setting higher (and thus getting a smooth relief) means that generating your final image takes longer. Fortunately, more recent versions of Blender have 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.

Denoising

A standard coarse render of 25 samples vs. the same render with noise reduction applied.


To turn on this option, you’ll need to go to the View Layer Properties, which you find by clicking on the grey icon of a stack of photographs. Once there, you can check the box for Denoising, which is a little ways down. 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.

NoiseCompare.jpg

Noise reduction on 10 render samples vs. on 100 render samples.

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).

Linear Heightmap Interpretation

We’re almost done changing settings, pulling levers, and adjusting dials. There’s one last one, and it’s one that escaped my notice for the first five years I used Blender.

Select the plane, go to your Shader Editor, and have a look at your Image Texture node. Change your Color Space from sRGB to Linear.

Linearset

Basically, we’re telling Blender to linearly convert each pixel in the heightmap to a displacement. If we don’t, it will apply a curve, instead, and a heightmap pixel that is, say, 50% grey, won’t necessarily be half as tall as the white areas. Setting it to linear makes it function more sensibly: the height of each pixel of terrain is always in exact proportion to where it falls on the white-black greyscale ramp. Notice the different it makes.

Compare

The original, sRGB setting is on left. Linear is on the right. Now the lowlands suddenly get a lot more detailed. This is a critical setting to get right, or Blender will interpret your terrain wrong and artificially flatten out your lowlands.

I was going to tell you about this a while ago, but I held off because (1) I wanted to reduce the number of settings you had to tweak before you actually started making real relief, and (2) I discovered this later and didn’t want to update all the screenshots to show what it would look like with the new relief. By this point, I figure it won’t bother you too much to know that the last few screenshots in the tutorial have the flatter relief.

Final note: This setting seems gets reset every time you load a new heightmap in, so you’ll need to remember to update it each time you make a relief of a new area.

Saving the Relief

Now that all the settings are tweaked, we can do one final render that we’re happy with. Now is a good time to crank up the number of render samples, and you might also want to scale the render size back up. If you remember before, I went to my Output Properties (the grey icon that looks like a photo coming out of a printer) and set my output size to be 50% of the size that I wanted my final image to be. Now I could go back in and crank that up to 100%, if I’m thinking this will be the final image I render.

Once you’re set with that, go to the top menu and once again choose Render → Render Image. It might take a bit to produce this higher-quality image, but hopefully the results will be worth it. If, at any time in the render process, you decide you want to bail out and stop it from finishing, just hit the Escape key.

After it’s done rendering, we need to save our relief. Go to the top menu bar of the render window and choose Image → Save.

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.

Here, since I have only a greyscale image, I could probably choose the BW option to save without color, and make my file a little smaller. In any case, once you’ve got those settings to your liking, you can hit the Save as Image button way up in the upper right, 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 your Blender file 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.

  1. Change the dimensions of the plane to match the aspect ratio of your new heightmap.
  2. Edit your output dimensions in Output Properties, so that the final image matches your new heightmap.
  3. Edit your camera’s Orthographic Scale to match your new plane dimensions.
  4. Go to the Shader Editor and choose your new heightmap file.
  5. And don’t forget to change your color space back to Linear if Blender tries to reset it to sRGB.

You might also want to do some test renders while you tweak your vertical exaggeration (the Scale value in the Displacement node) 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