Transformations
Shaderlight will retrace if you transform (move, rotate or scale) geometry, or if you move the camera's viewpoint. Transforming an object means that the pixels in the image no longer have an accurate picture of what parts of the 3D scene might affect them. Moving the camera means that the contents of every pixel change, because every pixel is now “looking” at a different part of the scene.
Materials
Although the majority of parameters in Materials, Environment, Lights and Textures will update rapidly as a result of a MELT change, there are some that will take a little longer. As a general rule, items that change the direction or number of rays traced will mean that Shaderlight will have to re-trace some rays or trace some new ones. Examples are:
Things that change the number of rays traced in the scene:
| • | Making a surface reflective where it was previously matte. |
| • | Increasing the number of samples to improve the appearance of glossy reflections. |
| • | Altering the reflection falloff distance. |
| • | Introducing transparency where an object was previously opaque. |
| • | Increasing Ambient Occlusion samples. |
| • | Changing Ambient Occlusion maximum distance. |
Things that alter the direction of rays traced in the scene:
| • | Increasing the roughness of a reflective Art Professional material. |
| • | Increasing the amount or position of a bump map on a reflective surface. |
| • | Changing the amount or position of a displacement map. |
| • | Changing the Index of Refraction of a transparent object. |
Although these do require retracing some rays, or creating new ones, Shaderlight intelligent pixels mean that only the invalid parts of an image will be re-rendered.
Lights
Because lights often affect almost every pixel in an image, some changes to lights can cause a lot of new rays to be traced when changes are made. The most significant change will be when the number of Shadow Sample rays in an rectangular/area light or a Skylight is increased. In this case almost every pixel in the scene has changed. Shaderlight will attempt to make a MELT change, but there are conditions where a complete re-trace would produce the rendered image faster.
Miscellaneous
There are a number of actions which may have no influence on the image, but where it is difficult for Shaderlight to prove that the image will not change in advance. In these cases, Shaderlight performs a full retrace to ensure that the image is always correct. For example grouping or un-grouping objects, or adding a modifier to a mesh. For this release, Shaderlight will always retrace if it thinks there has been a change in the scene state, but we will be introducing more control over this in the future.
Page url: http://www.artvps.com/media/onlinehelp/index.html?what_doesnt_melt.htm