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Gather Node Part Two |
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Home > My Tutorials Part One: The Gather Node THE GATHER NODE PART TWO - THE SETTINGSNow we have examined where to plug the gather node, it is time to look at the four setting available to us. Raybias, MaxDist and Angle define which parts of your scene are searched for colours, while Samples defines how many rays are cast within that zone. In this sample, the green ball falls entirely within the area being gathered from, while the red ball is too close to the surface to be included. If the RayBias was reduced to zero, then part of the red ball would be included. If the angle was increased to 270 degrees, then the red ball would also fall within the gather zone.
SamplesThe Samples setting controls how many rays are cast. Increasing the number of samples has three effects. First, the time taken will be increased. Second, the overall effect of the gather will be smoother. Third, the overall effect of the gather will be more muted. The reason for effects two and three are central to understanding the gather node. Your final result will be the average colour produced by all of your rays. Those that do not hit an object, return as black. This is why low sample settings produce sparkly effects - at five samples, there is a good chance of three, four or even all five rays hitting the ball, producing a strong green result. There is just as good a chance of five misses, producing black. This can be seen on the first sample below.As you increase the number of samples, the more accurate a reflection of the colours within the gather zone will result. In this example, that results in a more subdued colour, as the changes of getting forty hits out of fifty on the green ball are much lower. One interesting insight into Posers inner workings comes if you increase the pixel samples in the render settings. One might expect this to have a similar impact to increase the samples settings, but it does not. All that happens is that the speckle moves around a little. This suggests that the random number generator in Poser is based on the pixel being rendered and the render setting, resulting in each pixel sample producing the exact same set of sample rays. The number of sample can have a massive impact on render speed. A scene that takes 25 seconds to render with 5 samples, slows to 30 seconds with ten samples, and to 71 seconds at 50 samples.
AngleThe Angle setting controls how wide an area the random rays will be cast within. It has no direct time impact.A low angle setting will increase the smoothness of the result, and can increase the impact, but only if the colours being gathered are directly above the pixel in question. One way to increase the speed of a gather node without losing the smoothness, is to reduce both the angle and the samples. RayBiasThe RayBias node controls how far about your surface the gather rays are sent out from. This is designed to prevent problems with displacement maps, but it can also be uses to increase the intensity of the gather. As you increase the RayBias setting, your start point will move nearer to the objects in your scene, increasing the intensity of the colour being picked up. However, set the raybias too high, and the gather node will ignore objects nearby and pick it's light up from distance sources. Here, as the RayBias is increased, the start point for the gather rays moves increasingly inside the ball, producing the brilliant red. By the time you reach a RayBias of about 5, the rays are starting above the ball, and completely ignore it! This can be used to create special effects. A high raybias, and an angle setting over 180 would all the gather rays to hit the back of objects above the surface! The speed implications of different RayBias settings will depend entirely on your scene. |
