水面(Water)


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現在、水面を作成する方法は2つあります:
  • サイズが調整可能なビルドインの"Lake object(円盤状の平らな水)"を作成する。
  • 地形に『Water Shader』を適用し、配置をコントロールするための『blend shader』やマスキングからなる他の形態を使用する事が出来ます。
"Lake object"によって、異なる高さと異なる色や波の特性を持つ複数のユニークな水のエレメントを作成する能力を持っています。また、河川、複雑な湖の形状、およびその他の重要なエレメント作成を可能にし、その分布を微調整するための水の形状をマスクする事が出来ます。実際にこれからどのように"Lake object"を使用するか、目を通しておきましょう。

First go to the Water layout so we can place the Lake object. It's the only option currently available on the Add Water Object menu and you will immediately see your 3D preview window covered with water when you add it. After you have done so, click on it in the node list to bring up its settings.

Most of the controls here are fairly self-explanatory. At the top the normal naming and enable/disable control. Handle In Preview determines whether the lake object itself will be shown in the viewport. Cast Shadows will be seldom used for now but its effect is fairly obvious - it makes the water disc cast shadows onto the terrain.

Moving on let's look at the settings on tne Transform tab. the Water Level is literally just the height of the object above the base planet surface (this will be important when transparency is introduced in later versions). The Centre settings control the X, Y, Z placement of the object and can be used when precise placement of your water is needed, but it's generally easier just to drag it around in the viewport. And finally Max Radius allows you to control the size of the lake object, measured in meters as usual.

The Planet and Surface Shader tabs are extremely simple. Planet allows you to specify the planet this water object is associated with. Because it's a flat disc it needs to be adjusted to fit the curvature of the planet, especially at large radius values, so it's necessary to connect it to a Planet to accomplish these changes. The Surface Shaders tab simply defines the shader for the lake object; naturally it defaults to a Water Shader.

Now that we've looked over the basic settings let's do a quick render to see how the water looks. Keep in mind that the default camera perspective is 1 kilometer above the terrain, so let's move down a bit to see the water better. Take the camera down until it seems fairly close to the water- about 200 meters - and do a render from this new camera position. At this height you should be able to see the wave structure as well as the wave variation which helps to increase realism. You'll no doubt find that water takes a bit longer to render than most other scene elements. Reflections are always quite demanding to render and Terragen 2 is no exception, but this aspect will be getting a lot of optimization in the future to improve things as much as possible.

You can control all aspects of the water surface itself in the Water Shader settings. Let's take a look there now and see what kind of things can be done with the current functionality. From the Surface Shaders tab click the box to the right of the Surface Shader name (Water shader 01) and select Go to [shader name] and the water shader settings window will then be opened. Aside from the standard node controls there are only two tabs here that allow you to control all aspects of your water. In the future additional functions such as transparency and shore surf/foam will probably have their own tabs here. For now the Wave tab is visible and contains some of the most important controls to adjust the look of our water.

By now you should be familiar with naming conventions of Terragen 2 so hopefully most of these will be self-explanatory. The Roughness setting controls the general roughness of the water surface and in combination with the Wave Scale and Smallest scale it determines the majority of the water shape. Wave Scale is the average wave size and Smallest Scale determines the size of the smallest details - increase this if the water shape looks too simplistic, but reduce it if you're only viewing the water from a distance as the smaller it is the more octaves in the Water Shader noise function and the longer render times will be.

The next set of controls should be familiar to users of Terragen 0.9 - the Wind Patch settings. In nature there are variations in wave structure and overall water smoothness across large bodies of water which is due to several factors including wind. These settings allow you to simulate those effects and bring an extra level of realism and needed variety and interest to large water elements. The defaults give a subtle variation to the water surface, modulating the roughness across the surface with a large-scale noise function. The Wind Patch Effect setting controls the strength of this effect - the actual amount of variation there will be between different areas. Wind Patch Size controls the average scale of the areas of variation. And finally Wind Patch Sharpness sets how sharp the line between areas of variation will be, or to put it another way it controls how smooth the transition between areas of different roughness is.

Now on to the Reflections tab. Master Reflectivity is fairly self-explanatory - it controls the overall level of reflectivity for the water. Index of Refraction is a technical term that refers to the amount of light refraction caused by a given material. This is implemented as the standard Index of Refraction where water is 1.33. The higher this is the more diffuse your reflections will be. Horizon Shift is a special function used to simulate the "shift" in reflection due to the aggregate effect of greater or lesser surface roughness on distant reflective surfaces. It will essentially shift the angle of distant reflection toward or away from the horizon. The easiest way to understand this is just to play with the slider and watch the effect on the preview. Highlight Intensity controls the strength of specular highlights from light sources and Min[imum] Highlight Spread allows you to control how much "spread" the reflections have - in other words how diffuse the specular highlights are.

Note that you can plug a shader into the Input of the Water Shader to override or contribute to many of these built-in settings. For example you can get more control over wave shape by plugging a Power Fractal into it and using the Displacement controls. A Heightfield Shader or Image Map can be used in the same way and can be particularly useful for explicitly controlling water shape. Another important capability enabled by the Water Shader Input is controlling the color of the water. Try plugging a Default Shader into the input and adjusting color - you now have the ability to specify any color you want for the water. This also gives us a springboard to our next experiment: masking the water to control its distribution.
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