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由Vray for SketchUp参数面板说开去




  1. 参数读取
    1. 默认参数预设
  1. 全局开关
    1. 全局照明=直接照明+间接照明
    2. 材质控制组
      1. 反射/折射
      2. 最大深度
      3. 最大透明级别，透明终止阈值
        1. 玻璃特写
      1. 贴图
      2. 贴图过滤
        1. 渲染时会对贴图纹理进行些许抗锯齿处理
      1. 模糊效果
      2. 覆盖材质
        1. 测试场景布光，180-220灰度
        2. 勿使用100白，因为颜色灰度影响场景光效果，过曝
    3. 间接照明控制组
      1. 不渲染最终图像
        1. 渲小图出大图
      2. 光线追踪控制组
        1. 二级光线偏移
          1. 控制反弹光偏移值，值越大漫射光越柔和，为零时图面光线会很硬朗
      3. 渲染控制组
        1. 批处理渲染
        2. 低线程优先
        3. 显示进程窗口
      4. 灯光控制组
      5. Gamma校正控制组
  2. 系统
    1. 最大树深度
    2. 最小叶片
    3. 面/级别
    4. 内存限制
    5. 区域划分
    6. 分布渲染
  3. 相机
    1. 默认相机使用场景
      1. 渲染人工光源的室内场景，如剧场室内（选择原因，不涉及太阳光）
      2. 渲染小体块分析图或家具设计，小东西，人工打光。（选择原因，不使用太阳光）
      3.  渲染夜景（原因同上）
      4. 使用HDR环境贴图作为光源（原因仍是不使用太阳光，这个不一定，有的HDR质量较高，阳光很充足，使用默认相机可能会过曝）
      5. 渲染鸟瞰，但是想获得手工模型感。（选择原因，不使用太阳光，人工光会改变模型的尺度感）
      6. 渲染立面图。（选择原因，物理相机无法看到平行投影的视角，因为光线无法聚焦，而默认相机可以，所见即所得。）
      7. 如果是做ao图，不可以关物理相机，而是去掉物理相机右下角的曝光
      8. 只要不使用Vray阳光系统，默认相机都能够比较好的完成任务，而且能解决轴测图，立面图的问题。这里的人工光指的是，Vray片灯，Vray点状灯（泛光灯）和Vray环境灯（GI灯）
    2. 相机类型
    3. 覆盖视野
    4. 物理相机
      1. 加载vray阳光
      2. vray物理天空贴图时时必须使用物理相机
      3. 覆盖焦距，快门，覆盖胶片宽度，变焦，光圈，感光度，Distortion，Lens shift，白平衡，曝光计算，镜头渐晕
    5. 景深和运动模糊
  4. 输出
    1. 覆盖视口
    2. 获取当前视口
    3. 发散知识，像素宽高比
    4. Render output
  5. 环境天空
    1. 天光
      1. HDRI素材
        1. 球状或是盒状
        2. 背景通道不影响亮度，影响反射
        3. 常用VRAY补光，线性衰减模拟太阳
        4. SKY注意SUN的SIZE
    2. vray灯光
      1. 现实中灯衰减，最起码是反比（inverse），真实的运算公式是平方反比（inverse square）
      2. vray泛光灯模拟路灯，台灯，不宜使用线性衰减
  6. 间接照明
    1. GI
      1. 用于视线分析
      2. 反射焦散
      3. 折射焦散
    2. 后期处理控制组
      1. 控制色溢
      2. 对比度
      3. 每帧保存贴图
      4. 首次引擎
      5. 二次引擎
    3. 细分
      1. 三等分
    4. 确定性蒙特卡罗
      1. 基于镜头采样
      2. 每个像素点的采样各自独立，渲染图像会有颗粒质感
      3. 对内存的占用较小，只计算一小块，算完一块，立刻释放内存
    5. 发光贴图引擎
      1. 基于镜头采样
      2. 有细节的地方，使用最大参数，没细节的地方，比如地面，使用最小参数
        1. 细节
          1. 就是图案复杂的地方（颜色突变多的地方，由颜色阈值控制）
          2. 边边角角，表面转折大的地方（法线变化速度快的地方，由法线阈值控制）
          3. 缝隙里（两表面距离近的地方，由距离阈值控制）
      3. 半球细分
      4. 样本
        1. 室内渲染酌情提高样本数和细分
      5. 显示样本
      6. 显示直接光照
      7. 二次反弹
        1. 首次引擎负责细部的光影
        2. 二次引擎的作用就是去尽可能收集这些不断反弹的，不断衰减的光线对于图面的贡献，来模拟真实
    6. 灯光缓冲引擎
      1. 基于相机采样
      2. 细分
        1. 测试渲染设置200-300，正图渲染1000-1200
      3. 尺度，取样大小
      4. 线程数量
      5. 储存直接光
      6. 显示计算阶段和自适应
  7. 图像采样器（抗锯齿采样器）
    1. 抗锯齿专题
      1. 根据光采样数据，在图像采样器中进行抗锯齿采样，并通过抗锯齿过滤器的算法表达出来
    2. 固定比率图像采样器
      1. 细分
        1. 默认细分为1，意思是，vray在确定图面的每一个像素的颜色时，会参考1个样本，图面会粗糙
        2. 测试参数1，调高参数4是可以看到平滑效果，正图参数一般16，因为速度慢，一般不用这个图像采样器
    3. 自适应DMC采样器
      1. 细分
        1. 通过最小细分和最大细分给采样器设定精度范围，噪波阈值控制噪点之间的色阶差，色阶差越小，颜色的过度就越平滑
      2. 噪波阈值
        1. 限制了图面的每两个像素之间最大的色阶差，决定了图面的精致标准，即“我希望图面有多精细”
      3. 最大细分
        1. 决定了封顶的精度，即“我实际上最多能有多精细”
      4. 参数设定
        1. 默认参数最小细分1，最大细分16，噪波阈值0.01，已经是正图参数了，想设定的更高，最大细分24，噪波阈值0.005
      5. 使用范围
        1. 非常适合材质光影复杂，模糊效果多的场景（因为在vray中所有的模糊效果都是由DMC引擎产生的，所以它在处理模糊数据时非常高效）
    4. 自适应细分采样器
      1. 原理
        1. 允许不足采样，在模型的边界，缝隙，转角，贴图处使用过采样（over sampling），在平整光滑的表面，使用不足采样（under sampling）在不足采样的地方，必须使用插补计算的方法编造出连续的色彩数据
      2. 参数设定
        1. 最小比率-1，最大比率2，就可以认为是正图参数了，更进一步的话，可以采用0，3的组合
      3. 使用范围
        1. 适于有大量平整表面的模型，贴图也不要很多，否则就没有效率了。它是渲染体块分析图的利器，速度快，表面会非常平滑，颜色过渡也会很完美
    5. 抗锯齿过滤器
      1. Catmull Rom
        1. 在大多数情况下，它会获得最清晰锐利的边缘，但是当场景中有明亮的自发光材质，毛发，或密集网格时，很容易造成这些细节的边缘过于夸张而走样
      2. Area算法
        1. 在1.5-0.5之间调整，数值越大越平滑，越小越锐利
      3. Box
        1. 在过滤区域内使用均等的权重把采样叠加在一起，在这些过滤方法中，Box是最快的，它的数值最好设置为1.0
      4. Triangle
        1. 使用了线性的曲线来影响像素，这样在采样区的边沿很少会发生过滤现象。Triangle过滤的数值最好设置为2.0
      5. Lanczos
        1. 使用了窄钟状曲线，这种曲线可以在采样区域的边沿产生负值，它的数值最好设置为4.0
  8. 渲小图出大图
    1. 产生原因
      1. 建筑表现图通常需要较大的分辨率，但是其实对于材质以及光影并不需要达到逼真的级别，对很多建筑人来说，图大而清晰就行了
    2. 思路
      1. 光采样和图像采样的过程分离，用一张小图采集的光数据，提供给大图进行图像采样
    3. 操作步骤
      1. 全局不渲染最终图像
      2. 输出面板选择光采样图幅大小，原则是边长大约在正图的三分之一到四分之一左右，长宽比与正图一致
      3. 设置间接照明引擎，必须是发光贴图+灯光缓冲的组合，发光贴图设置正图参数：最小比率-3，最大比率0，半球细分50，插补样本35，灯光缓冲细分800-1000，有需要的话请把取样大小改为0.01
      4. 保存发光贴图和灯光缓冲数据
      5. 取消全局不渲染最终图像
      6. 输出中设置正图的长宽
      7. 设置图像采样器为正图参数
      8. 设置发光贴图及灯光缓冲数据调用由“单帧”（Single Frame）改成“从文件”（From File）
      9. 点击渲染会看到vray直接跳过光采样过程开始出正图
    4. 优劣
      1. 光影会在细腻程度上有一些损失，但是图面的清晰程度非常高，非常节省渲染时间
  9. 颜色映射
    1. 本质
      1. 本质就是曝光
    2. 线性曝光（linear）
      1. 图面明暗反差会非常强烈，光感会很强，但是容易过曝或死黑
    3. 指数曝光（exponential）
      1. 最大限度的保留细节的范围，但是图面会比较灰，明暗对比不强，需要后期调整对比度
    4. 莱因哈德（reinhard）
      1. 倍增值1，混合值（burn value）0.8。可以折中上两种曝光算法
  10. DMC采样器
    1. 各采样器比较
      1. 自适应细分是一个几乎所有其他“有偏差的非物理渲染器”（注1）都在采用的算法。它是一种相对来说有点老式，但在绝大多数情形下都非常好用的算法。它会算出干净且采样细致的图像结果，在静帧渲染时的表现非常出色，但是与DMC采样器相比，自适应细分往往会在一些本可以采样再少一点的地方过多采样
      2. DMC采样器，那么要在某些同样的地方求出同样质量的反射模糊可能就不用这么多样本，DMC是目前在求取镜头景深和三维运动模糊时最好用（时间短质量高）的光线追踪采样算法
    2. 详解见下一篇

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Interview with Steve Jobs, WGBH, 1990

Interviewer: what is it about this machine? Why is this machine so interesting? Why has it been so influential? Jobs: Ah ahm, I'll give you my point of view on it. I remember reading a magazine article a long time ago ah when I was ah twelve years ago maybe, in I think it was Scientific American . I'm not sure. And the article ahm proposed to measure the efficiency of locomotion for ah lots of species on planet earth to see which species was the most efficient at getting from point A to point B. Ah and they measured the kilocalories that each one expended. So ah they ranked them all and I remember that ahm...ah the Condor, Condor was the most efficient at [CLEARS THROAT] getting from point A to point B. And humankind, the crown of creation came in with a rather unimpressive showing about a third of the way down...
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