With just volume scatter (left), the input color is only visible on parts of the volume where the camera ray got scattered directly into the light. 2.21a) The demo scene with just one white area light on the right. Hint: If you want to color a scattering volumetric material like dust or smoke, combine the volume scatter shader with a volume absorption shader using an add(!) shader node:įig. Notice how negative anisotropy results in an almost reflective appearance of the volume while positive values cause the light behind the object to tint it. For this scene the only light sources are two point lights: a blue one in front of the object and a red one right behind it. From left to right the anisotropy was increased. 2.20) Renderings with a volume scatter material. Since there is no color, there is no complementary color, either (compare this to fig. 2.19) Volume scatter material with no color but 80% grey instead. The grey parts are where the scattered powder blue mixes with its complementary color, which is most visible for high densities.įig. The color of the shader is the same powder blue I use for all of the test renderings, the appearing color however is its complementary color, since blue got scattered away. Notice that a volume scatter material with a high density looks fairly similar to the diffuse shader. Top down the anisotropy was set to -1, -0.5, 0, 0.5 and 1. From left to right the density was increased, the values were: 1, 10, 25, 50, 500. 2.18) Renderings with a volume scatter material. Depending on the density, rays might not get scattered at all.įig. Anisotropy of 0.0 (center) will result in random scatter directions. Negative values mostly scatter into the opposite direction (right). For positive values (left), rays mostly get scattered along the direction of the ray that entered the volume. However it is important to understand anisotropy as it can be tricky without first seeing its effects, so let’s take a look at some examples:įig. So in an evenly lit scene it does not make that much of a difference. Positive values let the ray scatter in the direction it is traveling, while negative values cause the ray to scatter opposite of its travel direction. A map could be a 3D (procedural) texture or the factor from a smoke or fire simulation.Īnisotropy is the scattering direction depending on which way the light ray is moving. If you want to vary the density of your volume in different areas, use a map for the density. You can think of this as adding more “dust” to a dusty room. The input can be an RGB or any texture.ĭetermines how thick the volume appears to be. Simply controls what color or light will be reflected by the volume. The possibilities of the volume scatter shader include anything from sunbeams (a.k.a. Similar to how the light from that window reflects off all of the tiny dust particles and appears to form a shape, volume scattering in Cycles can be thought of as light reflecting off of many tiny dust particles. A great example of this effect is a very dusty room with sunlight streaming in from a window. Although both tests are correlated, some differences in stereo processing are seen, depending upon whether or not the stimuli are presented near the point of fixation.When light passes through certain objects, it may seem as if the light itself is actually visible. In each case, subjects indicate depth by setting a rectangle (with fixed base) to match the perceived depth. The second test involves judgments of volumetric stimuli, seen stereoscopically. The first test is based on depth judgments of two bars relative to a fixation point. Here we offer two easy-to-administer tests for stereoanomaly. Because anomalies provide useful information about perceptual mechanisms, tests that measure and quantify the extent of a blindness are important investigative tools for research. In some cases, the sign of the disparity will be confused, and the perceived depth will be incorrectly seen as 'behind' rather than 'in front of' the fixation point, for example.
However, about 30%, of the population exhibit some form of stereoanomaly even for very small disparities, provided eye movements are avoided. Typically, such disparities are seen at the same depth as monocular stimuli.
In the absence of eye movements, everyone suffers from stereoanomaly for extremely large disparities. Stereoanomaly is the failure to see differences in depth when the viewer is presented with stimuli having different magnitudes of stereoscopic disparity.