..::snowy landscape::..

Being winter at the moment, and some people not having seen snow for absolutely ages (especially in the UK) this kind of question tends to surface quite a lot. The main trick to producing a convincing effect is the amount of irregularity and space. This basically means that you should really have a combination of the two – several pointy mountain ranges and vast open spaces. This therefore gives the viewer a sense of scale to the image, especially if you have introduced several volumetric effects to indicate the scene’s scale and “depth”.

Starting out with a single plane object, we can work in the Viewport at a lower resolution and render out with the poly counts cranked right up. The density spinner in the plane’s render section is ideal for this as we can increase this factor and not have any degradation in speed while working in the Viewport. If you’ve got a decent enough graphics card however, I would suggest that you at least preview how it’s going to look like before rendering, so crank the main geometry count up and tweak the settings to your liking to see how they interact with the rest of the scene. The easiest way to model! (Just don’t forget to turn them back down again, else the density setting will increase the number of polygons in the final render to something ludicrous!)

To create the desired effect, we will have to mix and mask various procedural maps. A small noise map will take on the form of our main displacement method. However, due to it’s size and the intensity of the displacement, when assigned it appears to be more of a large noisy mess than a mountain range! Therefore this noise map needs to be masked off. As we’re trying to do this procedurally, we can use a larger noise map to mask off random areas of the small noise map, thus creating large expanses of flat (ish) terrain.

Looking at our displacement, it’s almost there, but still doesn’t seem quite right – even though the noise is procedural, it still appears a little too intense and regular. It needs to be broken up a little more, and the large expanses need to be deformed a little. Therefore we can introduce another noise map, the same small size as the first, but offset by using a different phase. This will break up the terrain a little more by subtly subtracting displacement from the mesh, and breaking up the surface a little.

Finally, we can chisel crevices and displace the mountains in our terrain by overlaying an extra displace modifier on top of the original one. Within this new modifier sits another noise map, this time with a slight difference between the high and low values to reduce any falloff or “grey areas” around the noise. Using this sharp falloff within the displace modifier generates a steep bank which, if the amount of levels is turned up, can create an interesting result.

To create the best effect, we would have to turn up the render Density multiplier of the plane primitive to generate a polygon count around 1 million. This may seem like a ludicrous amount, but as there is little else in the scene at the current time, the amount of time it takes to calculate the mesh when preparing to render isn’t all that much. Granted, it’s higher than having a lower polygon version, but the effect is lost somewhat on lower polygon planes. Another alternative would be to use material displacement at render time instead of a displacement modifier. This can yield even better results due to the amount of detail this type of displacement can generate. However, the initial mesh preparation at render time may take a lot longer than before, but the results are worthwhile if you’re willing to wait.

	In the Top Viewport, create a Plane Standard Primitive. Set the Length and Width spinner settings to 1000 and the Length and Width Segs spinners to 100. Set the Density spinner to 8. This will add extra segments to our plane at render time without affecting the mesh displayed in the Viewport.
	Add a Displace modifier and rename it to Mountain Displace. Set the Strength spinner to 500. In the Materials Editor, create a new Mask map in one of the materials and label it “Hill Displace”. Add a Noise map to the Mask’s map slot and label it “Jagged Rocks”.
	In the Jagged Rocks Noise map, set the Noise Type to Fractal, the Size to 50, the Levels to 10 and the Phase to 5. Amend the Output Colour Map’s curve so it represents that illustrated in the screenshot. In the Hill Displace mask’s Mask slot, add another Noise map and label it “Jagged Rocks Mask”.
	Set the Size to 200, Noise Type to Fractal, Levels to 10 and Low to 0.5. Add a Noise map to the Colour #1 slot and label it “Jagged Rocks Offset”. Set the Noise Type to Fractal, Size to 50, Levels to 10 and Phase to 20. Set the Colour #2 RGB swatch to RGB 22,22,22 (a dark grey). Next, drag the entire Hill Displace map (not the material) to the Mountain Displace modifier’s Map slot. Select Instance Copy when prompted.
	Add a new Displace modifier and label it “Crevice Displace”. Set the Strength to 500, check on Luminance Centre. In a new material, create a new Noise map and Label it “Crevice Displace”. Set the Noise Type to Turbulence, Size to 200, High to 0.25, Low to 0.15 and Levels to 10. Set the Colour #1 swatch to RGB 117,117,117 and the Colour #2 swatch to RGB 128,128,128 .
	Finally, drop the Crevice Displace map to the Crevice Displace modifier’s Map slot. This second displacement is overlaid on top of the existing one, therefore lowering the mountains in areas.
	The final render. Motion blur is added to give the impression of us rushing over the surface. There are two types of material assigned; a smooth snow surface texture and a cloned version with a high and large procedural bump texture.

..::tips::..

You can create an effective time-lapse weathering effect on the ground plane by animating the High and Low noise thresholds so that the value between the two remains relatively constant (approx 0.1 difference between the two). This can give the impression of the crevice’s eroding away over millions of years. Add to this an animated weathering / construction of the mountains and you’ve got a very effective animation!

If you decide to texture the mesh, try adding multiple layers of noise maps. One base layer should be set to a low noise size with a low specularity to create the illusion of virgin snow, with a slight bump to indicate snowdrifts and terrain underneath the snow. The second material could be a mixture of two materials; namely snow with a large procedural bump assigned to generate the impression of a previous avalanche or snow on hilltops. The other material could be a rocky texture, visible under the snow on the mountains. The rough snow could be applied to this material using a Blend material with a smoke or turbulent noise map as the mix map.

Create additional environment effects by using a Volume Select modifier to select the faces of the topmost mountain peaks. You can then create a facing particle system and, with a white dusty material setup assigned to the particle system, generate effective snow being blown off the mountains. The same effect could be reworked to create snow being blown across the virgin snow.

Add the final touch by adding a hemisphere skydome to the scene with a slight colour gradient from light blue to blue to emulate the horizon and desaturation of colour. Also, amend the ranges of your scene’s camera so they extend beyond the hemisphere, and add exponential Environment fogging to create the impression of mist and snow dust in the background. This will also help blend the join between the land and sky a little so the scene appears more realistic. Finish the entire scene with a bright sun at approx 10 o’clock and a blue tinted dome of lights to emulate global illumination and uplights strategically situated to simulate light bouncing off the snow onto the mountains.

Initially published: 3D World magazine, Issue 37, April 2003.

Copyright © Pete Draper, April 2003. Reproduction without permission prohibited.

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