Cubemap

http://docs.unity3d.com/Manual/class-Cubemap.html

Cubemap

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A Cubemap is a collection of six square textures that represent thereflections on an environment. The six squares form the faces of an imaginary cube that surrounds anobject; each face represents the view along the directions of the world axes(up, down, left, right, forward and back).

Cubemaps are often used to capture reflections or “surroundings” of objects; for exampleskyboxes and environment reflections often use cubemaps.

Cubemapped skybox and reflectionsCubemapped skybox and reflections

Creating Cubemaps from Textures

Preferred way of creating cubemaps is importing them from specially laid out textures.Select Cubemap texture import type and Unity should do the rest. Several commonly used cubemap layouts aresupported (and in most cases detected automatically).

Cubemap texture import typeCubemap texture import type

Vertical and horizontal cross layouts, as well as column and row of cubemap faces are supported:

Another common layout is LatLong (Latitude-Longitude, sometimes called cylindrical). Panorama images areoften in this layout:

SphereMap (spherical environment map) images can also be found:

By default Unity looks at the aspect ratio of the imported texture to determine the most appopriate layout fromthe above. When imported, a cubemap is produced which can be used for skyboxes and reflections:

Selecting Glossy Reflection option is useful for cubemap textures that will be used byReflection Probes. It processed cubemap mip levels in a special way(specular convolution) that can be used to simulate reflections from surfaces of different smoothness:

Cubemap used in a Reflection Probe on varying-smoothness surfaceCubemap used in a Reflection Probe on varying-smoothness surface

Legacy Cubemap Assets

Unity also supports creating cubemaps out of six separate textures.Select Assets > Create > Legacy > Cubemap from the menu,and drag six textures into empty slots in the inspector.

Legacy Cubemap InspectorLegacy Cubemap Inspector
Property:Function:
Right..Back SlotsTextures for the corresponding cubemap face.
Face SizeWidth and Height of each Cubemap face in pixels. The textures will be scaled automatically to fit this size.
MipmapShould mipmaps be created?
LinearShould the cubemap use linear color?
ReadableShould the cubemap allow scripts to access the pixel data?

Note that it is preferred to create cubemaps using the Cubemap texture import type (see above) - thisway cubemap texture data can be compressed; edge fixups and glossy reflection convolution be performed;and HDR cubemaps are supported.

Other Techniques

Another useful technique is to generate the cubemap from the contents of a Unity scene using a script.The Camera.RenderToCubemap function can record the six faceimages from any desired position in the scene; the code example on the function’s script reference pageadds a menu command to make this task easy.

### 立方体贴图的概念与用法 立方体贴图是一种用于图形编程中的技术,主要用于模拟环境映射效果。它由六个正方形纹理组成,这些纹理共同形成一个包围对象的立方体[^1]。通过这种方式,立方体贴图能够提供一种高效的方式来表示周围环境的反射特性。 #### 静态与动态立方体贴图的区别 静态立方体贴图是在开发阶段预先生成并存储好的纹理数据。而动态立方体贴图则是在程序运行时实时生成,因此它可以捕捉到场景中移动的对象及其变化的效果。然而,由于每次渲染都需要重新计算六张不同的视图,这种方法会显著增加GPU的工作负载。 为了优化性能,在实际应用过程中通常采取一些折衷方案: - 对于重要且需要精确反映周围情况的目标采用动态方法; - 而对于那些不太显眼或者距离较远的对象,则继续沿用预烘焙好的静态版本以节省资源开销。 此外,调整贴图分辨率也是一个有效的策略——降低其大小(例如从常见的512x512降至256x256),虽然可能会牺牲部分视觉质量,但却能有效减少像素着色器调用次数从而提升效率。 以下是创建简单立方体贴图的一个Python伪代码示例: ```python def create_cube_map(size, dynamic=False): textures = [] if not dynamic: # Load pre-made static cube map textures. for i in range(6): # Cube has six faces. texture_path = f'static_cubemap_face_{i}.dds' loaded_texture = load_texture(texture_path) textures.append(loaded_texture) else: # Render each face dynamically at runtime. for direction in ['front', 'back', 'left', 'right', 'top', 'bottom']: render_target = setup_render_target(direction, size=size) rendered_image = capture_scene(render_target) textures.append(rendered_image) return combine_textures_into_cubemap(textures) cubemap = create_cube_map(256, dynamic=True) apply_to_shader(cubemap) ``` 此函数展示了如何根据不同需求选择加载已存在的静态图像或是即时绘制新的动态画面作为最终产物的一部分。
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