Combining GI Methods |
It often is very efficient to mix to different engines: one for the primary and one for the secondary bounces, to have the advantages from both. One engine can be faster for one thing and the other for another aspect. If you select one or two GI methods you will see that the corresponding GI setting tabs will be visible, the non chosen GI methods will be hidden for more visible clearness.
VRAY can combine them in an intelligent way to give you high speed with very high quality at the same time, also for certain animation types it makes sense to mix fast smooth solutions with physical accurate ones p.e. Combining 2 engines for primary and secondary GI is actually the standard way to work in VRAYforC4D.
Irradiance Map & DMC
This is actually the default setting. The Irradiance cache is used for the primary GI, and DMC for the secondary bounces, the combination of the fast and smooth IR Maps and the very accurate and detailed DMC fits many scenes and can be used for stills and animation.
Depending on the settings you use this method can be extremely fast, also for previews, or can be a very detailed GI solution for ultra high quality, and of course all in between:-)
Also You can save the IR Map and reuse the saved GI file, also if you raise the final image resolution, you can still use a saved IR Map that was calculated at smaller resolution. A BIG advantage! In some cases it is better to save a detailed GI solution at small size (800x400 p.e.) and render the final image with the saved solution at full print size ( works with final outputs like 5000x2500pixel). this method brings higher(!) Quality than rendering the final 5000x2500 pixel with full site GI at lower GI setting.With this method you can also change the camera angle a bit, or adjust and change a materials and most of the time the IRMap will still get you good results.
A very flexible method.
Irradiance Map & Light Cache
This is a cool method to combine the great light cache with its “instant preview” capabilities with the smooth irradiance map.
The light cache resembles a bit the unbiased engines that are out there like maxwell render. there is also an option in it to render fully unbiased (PPT). however most of the time you want to combine high quality with good speed to get your projects out.In light cache you see a rough pixeled/noise image of the whole scene within seconds, basically thats already a good approximation how the scene will look like.
The longer you wait the more light is traced and the image will get more noise free, however in most light cache methods you will want to set the light cache to be rendering to a specific amount of light traces and then use another method to cleanup the image and make it smooth and noise free. the combination with irradiance map again is a very common one and combines very fast preview in the gi pass with high image quality.
The light cache is also very detailed in it settings. so you can also combine a very rough light cache with IRMap to get good and fast image results.
Always take care to set the number of passes to the amount of cpu`s you are using to get most speed out of light cache, if the result is too noise simple increase the sample size a bit. this makes the rendering also faster (you loose some image detail though)
DMC & Light Cache
Also interesting can be the combination with DMC, in this method you often use a very high DMC - AA setting to smooth out a very noise and fat light cache solution, the image quality can be very high through the combination with DMC.
Also Vlado famous universal setting is based on this combination.
Often you want to change the adaption of the DMC sampler settings in render settings tab / DMC sampler to 1.0 for this method. the internal DMC engine is therefore used not only for GI but also for AA and overall image sampling.
Possible is both having DMC for primary engine and light cache for secondary or also the other was around.
Light Cache & Light Cache
You can also combine 2 time light cache, this is also used to make vray rendering like an fully unbiased engine, using the PPT algorithms. Usually this method can take some time to cleanup noise,. good AA settings can help here.
Combinations with Photon Map
All methods can be combines with photon mapping,. for indoor solutions that do not use a sky photon mapping can have advantages, also some professionals long term vray users seem to like photon mapping in certain circumstances.
Not combining GI
Of course you can also decide to just use a primary GI engine. Just put the secondary to “none”.
This will result in poorer results of course but brings speed advantages. Specially for previews you can turn of the secondary engine, or if you have scenes that not at all use any glossy effects.
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