На форуме cgsociety.org нашел интересный пост на тему глобального освещения.
Adamt:
1) Use GI to assist a good light rig; don't rely too much on material illumination;
2) Use flat, white materials on everything while testing GI settings (except for saturation);
3) Never adjust more than one setting between test renders;
4) Keep a Min/Max ratio of at least 1:10 (usually closer to 1:5 and up to 1:1);
5) Start with low Quality/Samples and first establish a good brightness level and distribution;
6) Increase diffuse level if distribution is too low, but if you have to go over 3 try something else (e.g., increase GI output of walls, add low-level ambient light, or use low-power local lights);
7) Raise Quality/Samples enough so you can get a feel of your problem areas;
8) Raise them again and try some area renders until the problem spots have been minimized (you must work at or close to your final render resolution);
9) Recognize which settings resolve which artifacts:
* blotchy corners/details may mean Max or Samples is too low;
* blotchy flat areas may mean Min, Quality, or Samples is too low;
* fuzzy shadows may mean Samples is too low;
* a watercolor look could mean Quality or Samples is too low;
* it might be something else! (shadow bias/resolution for example);
10) Use compositing tags to optimize speed and quality:
* use tags with higher GI quality on problem objects;
* use tags with lower quality on objects that don't seem to mind;
* investigate the "seen by GI" setting--it doesn't do what you think it does;
11) Use Material>Illumination settings to optimize speed and distribution;
* you can generally turn off GI in chrome-type materials;
* you can generally turn off "Receive GI" in glass-type materials;
* you may be able to turn of "Generate GI" for glass, but you better check it;
* you can--and often must--adjust material saturation to control color bleed.
All of course IMHO.
*************Rendermania Tips*********************************
- lights in C4D have contrast, falloff and shadowmap resolution controls. use them.
- The default antialiasing setting in C4D is set to 100%. This will eat/oversoften any available texture detail if it isn't set lower. there are also different filtering algorithms to play with.
- if Mipmapping eats texture definition, it can be changed to SAT or other filtertypes for each material channel
- R9's micropoly displacement can add copious amounts of surface definition at rendertime that wasn't possible with R8. Its quite fast, and lighting/shadowmaps take the SPD into account. very useful for creating surfaces like grass, bark, cobblestone, fungus/organic/veined/rusty/fuzzy etc
- MR strikes me as having darker Gamma by default than C4D's renderer. It helps to set C4D's gamma down a notch or two, or even better, color correct C4D renders in Combustion. Digital Filmlab is good for adding soft diffusion/overexposure style effects to C4D renders
- C4D's Vector Motion Blur is good quality and fast, provided that the default settings are changed. Try 0.1 instead of 1.5 pixels for the sampling, and up the number of samples to 128 or higher.
- C4D's render engine doesn't tend to generate any grain by default. adding subtle grain in post helps achieve a more film/studio-render like look.
- for studio-quality renders, antialiasing needs to be set to 'Best'
- changing the aperture width of the camera rendered with can help give more sense of depth/scale. I tend to set mine to 70.
- if you can get away with widescreen (the client doesn't mind), setting the renderformat to HDTV or similar rather than 4:3 shaves quite a few pixels and thus rendertime off animations. sometimes the widescreen/letterbox format also gives the render a more cinematic feel.
- in some cases, more realistic colored lighting (e.g. daylight through a window) can be achieve by projecting a blurred texture from lights. create a new material. knock out all channels except 'transparency'. load a suitable texture into the transparency channel and drag and drop the material onto a light. it will now act like a light-gel (or a slide inserted into a projector). if the projected texture comes out too strong, turn the transparency channel into a 'layer' texture and adjust with brightness/contrast etc. the texture blur control can be used to diffuse the texture as well. HDRI's can be used as lightgels just like regular bitmaps.
- radiosity. mesh objects can act as lightsources when radiosity is switched on. create a material with only the luminance channel active. drop it onto an object in the scene. the object will now radiate light. how much it radiates can be controlled using the illumination controls in the material editor (or by putting different textures/noise in the luminance channel). 'receive GI' can be turned off since the object is a lightsource only. the compositing tag can be used to make the radiating object invisible to the camera (keep seen by GI, knock out seen by rays/camera). objects radiate more light if you make them bigger/wider. using this logic, characters can be lit using simple planes with luminance (simulating the reflector panels used to shoot actors in live action film shoots).
- radiosity 2. the number of diffuse bounces affects renderspeed and should be used carefully. for preview renders, pre-pass size can be set down to 1/10 and accuracy to 30 or so. it'll make the render a bit splotchier, but takes considerably less time.
- faking radiosity. if the desired effect with radiosity is to have light bounce off the floor to illuminate objects from beneath, this can sometimes be faked by creating a paralell light with no shadow that points straight up (or up at a slight angle). if specularity is switched off for this light and the light isn't excessively bright, it can give a bounced-light-from-beneath effect similar to what radiosity creates by default.
- faking radiosity 2. landscapes with trees can be quite difficult to light without radiosity. one way to fake it is to create a large light-ring. put an omni light inside a ring array object (no shadow). make the ring radius larger than the landscape. don't make the light too bright (as there's lots of copies of it in the ring). adjusting the altitude of the ring can help simulate different types of atmospheric lighting. or one can use a smaller ring-light just like the ones used in music videos. also, C4D allows for light inclusion/exclusion, so things like trees and huts etc can be lit with their own light-rings without affecting everything else.
- sunlight in general. the sun object in C4D can be difficult to control. its easier to control lighting/shadows using a strategically placed omni light with a high-res shadowmap. again, a lightgel can be used to project a subtle texture and thus make the colored lighting more uneven. turning light visibility on (but down to something like 20% brightness) can help fake a bit of light-haze. an added ambient light can help give more of a sense of atmospheric lighting, but should be very subtle (perhaps with specularity turned off). the quality of sunlight can be controled to some extent using the 'contrast' setting for the light. lower contrast makes the light more diffuse.
- material settings. two of the most important controls for creating realistic materials are the specularity channel and 'diffuse falloff' in the illumination channel. setting the diffuse falloff value lower means that shading will fall off more sharply. this can be good for creating certain types of materials. a lot of objects in real life don't have much in the way of sharp specular highlights. this can be controlled by setting the specularity height lower and the width wider in the specularity channel.
- ramps. Maya artists tend to use ramp shaders a lot. the same can be done in C4D by using 'layer' materials and adding a light-to-dark 'gradient' on top of the stacked materials (using a mode like multiply to 'burn' it into the texture). the direction of the gradient can be used to create landscape textures for example, that darken/lighten at different altitudes. its also interesting to combine gradient + noise in some cases.
- dirtying objects up. for things like landscapes, where texture repetition tends to show if one isn't careful, it can help to put some light noise in the diffuse channel to make the texture/lighting a bit more uneven.
- volume water. a touch of subsurface scattering with a dark to light gradient can help give water more sense of volume. a cube needs to be used rather than a plane. very good for things like pool water lit from below.
Adamt:
1) Use GI to assist a good light rig; don't rely too much on material illumination;
2) Use flat, white materials on everything while testing GI settings (except for saturation);
3) Never adjust more than one setting between test renders;
4) Keep a Min/Max ratio of at least 1:10 (usually closer to 1:5 and up to 1:1);
5) Start with low Quality/Samples and first establish a good brightness level and distribution;
6) Increase diffuse level if distribution is too low, but if you have to go over 3 try something else (e.g., increase GI output of walls, add low-level ambient light, or use low-power local lights);
7) Raise Quality/Samples enough so you can get a feel of your problem areas;
8) Raise them again and try some area renders until the problem spots have been minimized (you must work at or close to your final render resolution);
9) Recognize which settings resolve which artifacts:
* blotchy corners/details may mean Max or Samples is too low;
* blotchy flat areas may mean Min, Quality, or Samples is too low;
* fuzzy shadows may mean Samples is too low;
* a watercolor look could mean Quality or Samples is too low;
* it might be something else! (shadow bias/resolution for example);
10) Use compositing tags to optimize speed and quality:
* use tags with higher GI quality on problem objects;
* use tags with lower quality on objects that don't seem to mind;
* investigate the "seen by GI" setting--it doesn't do what you think it does;
11) Use Material>Illumination settings to optimize speed and distribution;
* you can generally turn off GI in chrome-type materials;
* you can generally turn off "Receive GI" in glass-type materials;
* you may be able to turn of "Generate GI" for glass, but you better check it;
* you can--and often must--adjust material saturation to control color bleed.
All of course IMHO.
*************Rendermania Tips*********************************
- lights in C4D have contrast, falloff and shadowmap resolution controls. use them.
- The default antialiasing setting in C4D is set to 100%. This will eat/oversoften any available texture detail if it isn't set lower. there are also different filtering algorithms to play with.
- if Mipmapping eats texture definition, it can be changed to SAT or other filtertypes for each material channel
- R9's micropoly displacement can add copious amounts of surface definition at rendertime that wasn't possible with R8. Its quite fast, and lighting/shadowmaps take the SPD into account. very useful for creating surfaces like grass, bark, cobblestone, fungus/organic/veined/rusty/fuzzy etc
- MR strikes me as having darker Gamma by default than C4D's renderer. It helps to set C4D's gamma down a notch or two, or even better, color correct C4D renders in Combustion. Digital Filmlab is good for adding soft diffusion/overexposure style effects to C4D renders
- C4D's Vector Motion Blur is good quality and fast, provided that the default settings are changed. Try 0.1 instead of 1.5 pixels for the sampling, and up the number of samples to 128 or higher.
- C4D's render engine doesn't tend to generate any grain by default. adding subtle grain in post helps achieve a more film/studio-render like look.
- for studio-quality renders, antialiasing needs to be set to 'Best'
- changing the aperture width of the camera rendered with can help give more sense of depth/scale. I tend to set mine to 70.
- if you can get away with widescreen (the client doesn't mind), setting the renderformat to HDTV or similar rather than 4:3 shaves quite a few pixels and thus rendertime off animations. sometimes the widescreen/letterbox format also gives the render a more cinematic feel.
- in some cases, more realistic colored lighting (e.g. daylight through a window) can be achieve by projecting a blurred texture from lights. create a new material. knock out all channels except 'transparency'. load a suitable texture into the transparency channel and drag and drop the material onto a light. it will now act like a light-gel (or a slide inserted into a projector). if the projected texture comes out too strong, turn the transparency channel into a 'layer' texture and adjust with brightness/contrast etc. the texture blur control can be used to diffuse the texture as well. HDRI's can be used as lightgels just like regular bitmaps.
- radiosity. mesh objects can act as lightsources when radiosity is switched on. create a material with only the luminance channel active. drop it onto an object in the scene. the object will now radiate light. how much it radiates can be controlled using the illumination controls in the material editor (or by putting different textures/noise in the luminance channel). 'receive GI' can be turned off since the object is a lightsource only. the compositing tag can be used to make the radiating object invisible to the camera (keep seen by GI, knock out seen by rays/camera). objects radiate more light if you make them bigger/wider. using this logic, characters can be lit using simple planes with luminance (simulating the reflector panels used to shoot actors in live action film shoots).
- radiosity 2. the number of diffuse bounces affects renderspeed and should be used carefully. for preview renders, pre-pass size can be set down to 1/10 and accuracy to 30 or so. it'll make the render a bit splotchier, but takes considerably less time.
- faking radiosity. if the desired effect with radiosity is to have light bounce off the floor to illuminate objects from beneath, this can sometimes be faked by creating a paralell light with no shadow that points straight up (or up at a slight angle). if specularity is switched off for this light and the light isn't excessively bright, it can give a bounced-light-from-beneath effect similar to what radiosity creates by default.
- faking radiosity 2. landscapes with trees can be quite difficult to light without radiosity. one way to fake it is to create a large light-ring. put an omni light inside a ring array object (no shadow). make the ring radius larger than the landscape. don't make the light too bright (as there's lots of copies of it in the ring). adjusting the altitude of the ring can help simulate different types of atmospheric lighting. or one can use a smaller ring-light just like the ones used in music videos. also, C4D allows for light inclusion/exclusion, so things like trees and huts etc can be lit with their own light-rings without affecting everything else.
- sunlight in general. the sun object in C4D can be difficult to control. its easier to control lighting/shadows using a strategically placed omni light with a high-res shadowmap. again, a lightgel can be used to project a subtle texture and thus make the colored lighting more uneven. turning light visibility on (but down to something like 20% brightness) can help fake a bit of light-haze. an added ambient light can help give more of a sense of atmospheric lighting, but should be very subtle (perhaps with specularity turned off). the quality of sunlight can be controled to some extent using the 'contrast' setting for the light. lower contrast makes the light more diffuse.
- material settings. two of the most important controls for creating realistic materials are the specularity channel and 'diffuse falloff' in the illumination channel. setting the diffuse falloff value lower means that shading will fall off more sharply. this can be good for creating certain types of materials. a lot of objects in real life don't have much in the way of sharp specular highlights. this can be controlled by setting the specularity height lower and the width wider in the specularity channel.
- ramps. Maya artists tend to use ramp shaders a lot. the same can be done in C4D by using 'layer' materials and adding a light-to-dark 'gradient' on top of the stacked materials (using a mode like multiply to 'burn' it into the texture). the direction of the gradient can be used to create landscape textures for example, that darken/lighten at different altitudes. its also interesting to combine gradient + noise in some cases.
- dirtying objects up. for things like landscapes, where texture repetition tends to show if one isn't careful, it can help to put some light noise in the diffuse channel to make the texture/lighting a bit more uneven.
- volume water. a touch of subsurface scattering with a dark to light gradient can help give water more sense of volume. a cube needs to be used rather than a plane. very good for things like pool water lit from below.