IBL v's TA Lighting Techniques
Five subjects, each rendered once with a combination direct light from IBL (Image Based Lighting) and Bryce sunlight and then with a combination of TA(True Ambiance) and Bryce sunlight.
Each of the ten scenes has been optimised to off the best performance for the rendering method employed.
IBL has the advantage of being able to utilise the influence control and exclude the cloud slab from the direct lighting generated from the HDRI (High Dynamic Range Image) background. But the disadvantage for the light from the background when using direct a direct lighting approach is that it cannot scatter from one adjacent surface to another, the diffuse light can only travel from the background source to the illuminated surface. As a result IBL is best suited to open environments where there are few caves or pits which do not have unobstructed view of the sky.
TA had the advantage of being able to simulate light scattering via a randomised light gathering process "probes" are fired from visible surfaces and collect information as a result of repeated collisions with neighbouring geometry (up to Max Ray depth). RPP (Rays Per Pixel) determines the number of "probes" generated and hence controls the quality of the lighting effect. Low values for RPP will degrade the image and introduce unsightly noise. For effective use of TA high RPP are recommended but at the cost of lengthy render times and also, because TA deals with what is literally visible in the scene, it cannot exclude objects as in IBL, this makes incorporating volumetric clouds into a TA render inadvisable as the scattered "probes" are easily mopped by the fluffy clouds resulting in potentially huge render times.
No one method is king, both have their place their strengths and weaknesses. This product is designed to demonstrate (as well as providing useful content from which to make your own scenes) how these can be used effectively on nearly identical subjects.
Generally speaking IBL is easier to set up and will provide faster results and works best of all with complex bumpy materials. IBL will co-exist with volumetric clouds if exclusion is used and will work happily alongside other lights. TA on the other hand is frequently fiddly to set up, often has longer render times and works best of all with complex geometries, simple materials and simple lighting.
With the advent of the 7.1 update, TA scattering correction (render options) and TA optimisation (IBL tab). A new and super powerful lighting option has emerged, it combines the best of IBL with the best of TA to give superior results - unfortunately it also combines the complexity of setting up both IBL and TA.
If you wish to come to an understanding of these render modes, please consider the lighting tutorials provided by Horo and for a condensed rundown of the varied potential of both IBL or TA and IBL and TA, please consider watching this tutorial:
- 10 Example Scenes (.BR7)
- 10 Matching Scene Renders (.BMP)