medzo wrote:Hi
I need some theory background. How photonmap influences on quality of image and final render time?
Does photon map affect splotches, light leaks, noise, does it affect the quality of contact shadows etc....
1. Splotches are affected by
- bad wire geometry
- small windows (for example in interiors) - why the best way is use Skyportals
- very strong lights (not physical)
- bad balance between lights (Environment light and lamps in interiors)
- bad setup in render
2. Noise doesn`t exist in Final Gathering (if it is , it is coming from physical lights: Area Lights, IES, because Noise is only one way to increase speed render. Also from not supported Nodes in LW or bugs)
3. Contact shadow are coming from low resolution of Final Gathering. To solve this problem You must decrease (0.03-0.05) Spatial Tolerance but then You must increase Final Gathering setup ...and Your render starts be slow
)
4. To receive perfect GI You can use :
- QMC (Uncache) - but still is potential dangerous because before that You must shot interpolated photos (so can even appear splotches or light leaks! - again Skyportals are welcome)
5. To receive really perfect Global Illumination You have to use Path Tracing (then You are not worry with amounts of photons - in Kray You can setup ZERO photons for Path Tracing because phase of shooting doesn`t exist . No worry also with light leaks, splotches - of course geometry must be still good)
How the number of cells affect the quality of render and render time - i think i have read on forum that the main factor in render time and quality of image is based on your FG settings - so how does photon map affect this?
If You use Photon Map (no Path Tracing) then is very important to get it possible clean (Skyportals are preferred) and also shoot big amount of photons (1 million minimum) to fill whole space visible by camera. Also size of cells are important: bigger make problem in Final Gathering to make good samples in shadows (because distances between photons are too big). Too small cells make splotches and difficulty with smoothing GI . I keep 300 mm for interiors and 600 mm for exteriors.
Generally Photon Mapping is big subject and complicate idea ...but I like this method : is clean and fast in good hands and with new updates in K3.0 can be really easy to use
Will try write down answer and post soon....