GUI - Photons tab

From Kray
Jump to: navigation, search

About

PhotonsTab.png

This section controls the first stage of rendering. The stage consists of two stages: Computing global PM (Photon or Light maps) and Precomputing irradiances. In the first stage photons are shot into the scene and evaluated. In the second stage the photons are filtered into irradiance map. For more information refer to Global illumination techniques in Kray.

GI resolution

GI resolution field is common for Photons and FG tabs. This allows user to easily rescale all GI parameters by changing GI resolution. For example if precache distance is set to 50% and GI resolution is 150mm that means that precache distance will be 50% of 150mm = 75mm.

Generally you can leave this on Auto unless in rare cases (where the scene is very big and the camera views a small detail of it) that an improper value is chosen by Kray.


Photon settings

Preview photons

Will show you a preview of photon shooting phase. This can take quite a bit longer than with Preview Photons OFF so turn it off once you don't need it anymore.

Photon preset

This selection list lets you choose predefined photon presets. When you choose Custom from the preset list advanced settings are unlocked.

Photon map/Light map

This let's you choose the mode for shooting photons. Photon map will shoot photons from light sources while Light map will shoot photons from camera. Generally Lightmaps make more efficient use photons, since photons are shot primarily to areas seen by the camera. To achieve similar efficiency with photonmaps you will have to use light portals. Photon maps do not support light from background but you can use a luminous dome instead.

Global photons

Controls the number of photons shot into the scene. The higher the number the longer it will take for Kray to shoot photons but the light estimation of the scene will be better. Usually the values vary between 100.000 and 1.000.000 photons.

Emitted/Received: since the number of photons that are shot into the scene and those that actually hit something may differ a lot Kray let's you choose preferred method. In emitted mode Kray will keep shooting photons until it has shot the number of photons specified by global photons setting. When received mode is selected Kray will only count those photons that actually hit objects in your scene.

Power

This value let's you increase or decrease the brightness of indirect light. Higher values make brighter indirect light while lower values will make it darker.

N

This value defines how many photons will Kray blur together to produce smoother irradiance.

Precache distance

This is the size of irradiance cells in the scene. The bigger the scene, the lower the accuracy of indirect light. Smaller precache distance will produce more cells and thus more accurate indirect light.

The value is a percentage of the GI Resolution. So if you have GI resolution of 1 meter and precache distance 50% the precache distance in 500mm.

Precache blur

Has similar effect as N value – it blurs irradiance, thus removing the irradiance splotches. It works faster than N but it may not produce as accurate irradiance because N depends on photon density, while precache blur depends on size of GI resolution. It is usually a good idea to keep a good balance between both values.

Use Autophotons

(Note: this is advanced setting which probably never needs to be changed)

Usually photons density is not even across the scene. It is high in some parts of a scene and low in the others. In such situation the constant size of a photon filter does not work well. Therefore it is better solution to adapt filter size to photons density.

When Autophotons setting is off you can manually control the filter size. Kray will use appropriate radius size between min and max values to find the number of photons specified by the N setting.

When Steps is bigger then 1 Kray tries to find the size of a filter radius that contains N photons. It will start with Min radius and increase filter radius Steps times unless it reaches Max radius.

When Autophotons is turned on, Kray will analyze photon maps before actual render and set all rendering critical parameters automatically.

Low and High percentages are equivalents of Min and Max radius, but they are expressed relatively to real photons density in the scene. If Low value is to big, regions in scene with high photons density (low radius) may contain to few (less then N) photons. If High value is to small, areas with low photons density (big radius) will contain much more photons then N.

Dynamic is equivalent of Steps, but it is automatically adapted to real distance between regions of high and low photons density. That means if for example Dynamic is set to 10 and density of photons is even on the scene, autophoton system will set Step to 1. But in the case when photons density vary in different parts of the scene, Steps value may be higher, but not bigger then 10. Too low Dynamic value may appear as noise on caustics. Too high value on the other hand may slow down rendering process.

Caustics settings

Caustics preset

This selection list lets you choose predefined caustics presets. When you choose Custom from the preset list advanced settings are unlocked.

Add to lightmap

Add to lightmap adds the light information of the caustics to the lightmap and it makes the caustics light contribute to the general lighting during FG process. This option is only available in lightmap mode, because Photonmap always includes caustics light.

Caustics photons

controls the number of caustics photons shot into the scene. The higher the number the longer it will take for Kray to shoot photons but the light estimation of the scene will be better.

Emitted/Received: since the number of photons that are shot into the scene and those that actually hit something may differ a lot Kray let's you choose preferred method. In emitted mode Kray will keep shooting photons until it has shot the number of photons specified by global photons setting. When received mode is selected Kray will only count those photons that actually hit objects visible in your scene.

Power

This value let's you increase or decrease the brightness of caustics. Higher values make brighter caustics while lower values will makes them darker.

N

This value defines how many photons will Kray blur together to produce smoother irradiance.

Use Autophotons

Same as Use Autophotons setting above.