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关于灯光 一次反弹与二次反弹的 Muliplier值问题
1、非封闭空间，由于没有很多物体做光线的反射，缺省的一次、二次反弹值都是一样的，这样可以弥补空间散失的反射光线。
可以出效果，但是觉得这样的效果很平淡。（建议不要这样用。）
2、非封闭空间，可以利用环境贴图做为补充照明，所以要把二次反弹值减小。（建议这样用）要点是把环境贴图和二次反弹值
联合在一起考虑。
3、封闭空间，环境贴图已经不起作用了，但是物体已经可以形成足够的二次照明，所以如果还是用缺省的值，二次反弹就会太亮，灯光布置足够多的时候，连一次反弹都会太亮。所以我的习惯是灯光亮度、一次反弹、二次反弹的值呈降幂排列比如：
1. 2\0.8\0.5。
也可用 0.7\0.7\0.5
灯光参数的意义
On - should be obvious
Double-sided - this has effect only on planar maps. It will make them cast light on both sides.
两面都发光。
Transparent - when this is on, the light will not be visible, but will cast light. This can be very useful for interior scenes - you can put transparent lights at the windows, instead of counting just on skylight.
不选中时，灯是可见的。选中时，灯不可见，可以用来模拟天光，窗口的进光
Ingore light normals - by default vray takes in account the angle between a shadow ray and the light. This produces a noisy image, even in areas that are completely lit (not in shadow). Turning this option on will make vray ignore this angle and will make the image less noisy (but not physically correct).
默认状态下，vray...（此处不明），这将产生麻点，即使在完全不在阴影中的区域内。勾选中后vray将不考虑这种这种地方，麻点会少点，（但物理上是不正确的）
No decay - by default vray lights become weaker as the distance from them increases - this is how lights behave in the real world. However, it may not be very convenient to work with. Turning this option on will cause vray to ignore this distance. You will probably have to adjust the Multiplier if you change this option. Also, it seems that using it causes some artifacts which we will try to fix.
不衰减
Store with irradiance map - this option allows you to store the diffuse illumination from a vray light in the irradiance map. It may be useful in fly-through animations.
与光照贴图一起保存，对游历动画很有用。
Type and Size I think are clear, with the exception of W size - currently it does nothing, since the two supported types need at most two dimensional parameters.
Subdivs - this controls the quality (graininess) of the shadows. Greater values will produce smoother shadows. The parameter determines the number of samples (per pixel) that vray will make in order to calculate the shadows (actually, this parameter is the square of the number of samples). vray may send less (but never more) shadow rays when possible without loss in visual quality.
控制阴影的质量。大点会光滑一点。与采样值的平方成正比。
Low subdivs - this is used instead of Subdivs for irradiance map calculations and also when the level of a ray becomes greater than the degrade depth (see below). Each intersection of a ray with a surface increases its ray level by one. For example reflections typically increase the level of a ray by one, and refractions - by two, since the ray needs to pass through the front and the back surface of the refractive objects.
这个看不懂，呵呵。
Degrade depth - this is the ray level after which Low subdivs will be used instead of Subdivs. In the recent version of vray, sampling is to a large extent handled automatically, so you can set this to a large value without performance loss.
这个好像说没用。嘿嘿。
小技巧：
1. 要获得较理想的光照效果还必须打开二次光照反射，速度将会急剧的下降 二就是加大min rate和max rate（最多到-2,-1，再加大就像brazil一样了），或在rate为-3,-2的情况下加大下面的Hspr细分值（默认为15,到25~30为佳，再大也会像b razil一样了……………… ）！
调试过程中可以暂时关掉二次反弹，正式渲染的时候再打开，不建议关掉二次反弹换取速度，会少很多效果的。
出现黑斑的处理方式：
1)、优化模型，去掉模型的相交，采取平接和稍微离开一点距离的方式。
2)、加大Irradiance里Hsps Subdivs的值。
2 即使是单色的物体，比如白墙壁，都不要仅给它MAX的基本材质，在DIFFUSE里给它一个白色的贴图图片，可以减少产生黑斑。
3, 草图计算时, 可先用 320x240 图幅计算光照贴图, (用此方法可加速, 也可将Min rate值设低, 例如为 –2 达到较好精度 ), 将光照贴图存盘,
根据vray作者的回答, 光照贴图及图幅的大小与出图的质量无关, 但是, 它们的渲染时间却不相同, 图幅越小, 时间越短, 具体原因如下:
(问: I have noticed that rendering the same scene using different size region devisions, you get significantly different rendertimes. I haven't noticed any loss in quality really either. Could someone explain to me why there is a difference in speed. Also, is there a loss in quality? In my simple test scene I don't see any, but maybe in a more complex scene it would be noticable
答: There should be no difference in the final image, no matter what is the size of your render regions. However, every region requires some setup time. Also, when you use antialiasing filters, there is a border around each region that needs to be additionally rendered so that the edges of regions blend smoothly. As the region size increases, this additional work takes less time compared to the total render)
草图计算参数 (处标注外,区域为默认值)
max/ min -7/-2 Interp. Samples: 100
下次正式计算时可调出, 正是出图是最好直接计算GI(时间奇长)
v-ray 入门（2）——景深
1、参考建立场景，并开摄影机的Environment Ranges下的show选项。在数值里填上合适的数值，这些数值控制取景范围。你会发现在视图中，有条黄线会随数值的更改会移动，根据调Near数值尽量把黄线放在Camera.target附近。当然也许你的场景中的Near数值会我不一样，没关系的。（Camera.target的位置其实代表的就是兴趣点，也就是渲染完最清晰的那部份）
2、打开渲染设制，在Filtering/DDF卷展栏下，勾选在Depth of field下的ON选项，然后在Focal dist里填入刚才那个Near数值，这样就决定了兴趣点的位置。也可以勾选Get from camera(直接从摄影点获取兴趣点),如果你勾选了Get from camera那么刚才的Near数值就不起作用了。（是不是有点多此一举？如果你做的是静帖，那么直接用Get from camera好了。）
3、 下面有两个数值值得注意。
Shutter size：它控制着取景深度，如果把这个数值调高的话，那个景深的程度会更大些。（效果上看，更模糊点。）Subdivs:这个数值控制着景深效果的极别，把它调高的，可取得更理想的画质，（图3是Subdivs=3的效果，图4是Subdivs=10的效果。当然会增加渲染时间。我认为最后渲染时，至少要把它设为8以上。
4. 焦点模糊速度很快。
A区是设置焦点模糊的，勾选ON就可以打开了，第一个按钮是设置焦距的
下面的勾，选取后就是以摄影机的落点为焦点。下来是快门的光圈尺寸，和现实中的摄影机一样，光圈越小越清晰，越大景深越
浅越模糊。B 区是过滤方式，选项很丰富，自己慢慢去试吧。评价是可用、好用、设置简单、速度飞快。
v-ray简单入门（3）——焦散。
要作出焦散效果: shadow要用vray shadow , 反射和折射贴图都要用vrAYMAP才行
焦散的参数简单得只有4个参数
Sph Subdivisions
越大越真实, 注意, 其值大小的2倍与渲染时间成正比
Multipler
越大焦散效果越明亮
Search Dist.
焦散光子的追踪影响的范围值, 调小了就会一个一个的光斑很明显，如果大一点速度就会明显下降，但是效果很好。
Max Photons
控制焦散效果的清晰与模糊, 越大, 越模糊, 其值为15时, Sph Subdivions 大于6000后才起作用, 但这时的焦散效果并不是太好
1. 勾选参数后，加大MULTIPLIER值到60000左右就可以出效果了，你颗狠心将其加到100000(最大值), 其速度仍然飞快.
注意: 渲染时间的平方与sph subdivs参数值的两倍成正比
2. 还有个办法是加大灯光的亮度然后调整灯光的衰减值，根据其官方范例的的灯光设置时,用vray light 将灯的强度调到20,000以上例如600,000，再打开灯光的指数衰减, 但是我想说的是如果这样设置将使灯光的摆放位置成为问题，因为有了衰减，灯离的远些就会使场景迅速变暗，而更糟糕的是就会出现你渲染的图里那种很亮的边缘（靠近灯光）而另一边很暗。
有办法可以解决此问题，就是灯光使用默认强度（一般为1.0），再到vray渲染面板， 在散焦一栏里将强度（英文是Multiplier)设为800000左右，就可轻松设置灯光了！欢迎指教！！
前一个方法简单一点，我常是两者合用。我发现它的好处是焦散的效果似乎能落在透明材质本身里面，这样玻璃的效果非常好。
Actually, for the past month or so, you haven't had to stick to the method in the documentation, new features have since been implemented to make that outdated.
You can use any of the max standard lights. I've had good success with caustics by using normal light values (eg multiplier 1, no decay etc) and boosting the caustics multiplier in the vray rendering parameters instead to 100000. I also find that decreasing the caustic search parameter to 1 or less and increasing the subdivisions and photons will give really nice clear sharp caustics (no blurry splodges of light)
Again I wish there was a feature to save the caustics map, similar to how you can save the irradiance map. Also would like to be able to tell vray which lights to cast photons, as I usually only want 1 or 2 lights to cast caustics..... not all of them |
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