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CG渲染的十大技巧

2011年08月01日 技术·Skills 暂无评论 阅读 1,695 views 次

Ten Things to Make Your Renders Suck Less

十大技巧让您的渲染水平变得更好

1) Motivate your lights – As much as possible, every light in your scene should have a logical source to it. Is your key light coming from a lamp? a window? the sun? Sure you’ll wind up cheating the position and intensity of lights a bit for a better look, but try to keep them logically consistent

1、合理布置灯光。越合理越好,场景中每个灯光都应该能代表现实中一个合理的光源。主光源代表一盏灯?一扇窗的透射?还是太阳?当然你或许会在灯光位置和强度上添加一点不合理性,以便得到更好的效果。但无论如何,要尽量保证这种性质在逻辑上是连贯的。

2) Don’t be afraid of the dark – Too much CG is over-lit (high key lighting). Let parts of the scene be under-lit, or drop into near black. You still want some shape in your dark areas/shadows, but it can be just the suggestion of forms. If you know an area will always be in near darkness, this is also an opportunity to save some time an not model/texture everything in this area to a detailed level.

2、不要惧怕黑暗。太多的 CG 作品主光源都爆掉了。试着让场景的一部分得不到足够的光照,或干脆让之接近黑色。但暗处依然需要表现出一些轮廓才行,只是为了表现那里还有东西。如果你认为某个区域始终是在暗处的,你就可以在建模的时候少一点细节,节省一些时间。

3) Dark scenes do not mean under-exposed scenes – If you have a night-time scene or a dark interior scene, don’t just turn down the intensity of all the lights and call it a day. Drop the intensity of your fill, and even cool your fills off with a blue tint, but keep some elements of your scene properly lit. A character that is lit from the side (or slightly from behind) with a full intensity key and then darker fills will look better than a character that is more front lit but with the key turned way down in intensity

3、黑暗的场景不等于昏暗的场景。如果你渲染一张夜景或是昏暗的室内场景,别只把灯光强度调小就完事儿了。降低填充光强度,甚至加一层蓝色给它降温,这都行。但别忘了给场景中某些元素足够的光照。用100%光照强度的主光源从侧面照一个角色(或者从后方微微透出来光亮),然后用较深的填充光填充整个躯体。这样做要比正面打弱光效果好得多。

4) Depth of Field – We are used to looking at images taken by a camera, and camera lenses are unable to keep everything in focus at once. Items that are too near or too far from the focal point have softer focus. This can be done in 3D (slow to calculate) or 2D (faster, but with more artifacts that have to be worked around). Also remember that you need to use a circle/bokeh blur, not a gaussian blur if you are doing this in comp.

4、使用景深。我们习惯于看相机照出来的相片,而相机每次是不能将所有东西抓到焦距之内的。离焦点太近或太远的物体会更模糊。景深效果可以用3D(较慢)或2D(较快,但更假,得花更多功夫修改)来实现。别忘了要用散景模糊,而不是高斯模糊。(译注:关于散景,Bokeh,可参考这里)

5) Keep your light sets separate – In real life, you often have to light your actors/subjects with at least some of the same lights that light your environment. But as a result you wind up having to set up all sorts of flags, diffusers, barn doors, scrims, etc. in order to keep the light at one intensity for one object in frame, and another intensity for other objects in the frame. If you separate out your environment and your subject where possible and light them with different sets of light, then you have more control over the lighting of each element. Each of your characters can be lit with their own set of lights as well. Most CG films I’ve worked on have a set of lights (key, fill, a couple of rim lights) for each character, and these lights are constrained to the center of gravity/placer of the character and move with that character (but don’t rotate.. they stay aligned to world space). This gives you a lot of control over each character’s lighting, and you can adjust one character without affecting the others. Also by rendering characters separately, you save a lot of time when you are tweaking lights. Then the characters are put together in the compositing program to create the final image.

5、将你的灯光设置分开。平时,人们一般会用一组同样的光源去照场景中的一堆人物/物体。但用这种方法,你必须为每一个灯光设置好种类,色散强度,照射目标,遮光幕什么的,才能保证每帧打到每个物体的灯光性质统一。如果你把整个场景(和各种物体,如果可能的话)分开,对它们分别设置光照,你就能对每个元素的光照有更好的把握。每个角色接受的光照都来自于单独为它配置的光源。我参与制作的 CG 电影中,每个角色都有独有的光照设置(主光,填充光,和一些背光)。这些光被限制朝向角色的重要部分,并且和角色一起移动

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