I'm trying to render a simple animation with comical characters. From the following images, you could see clearly Combines from the Half-Life universe, and a creature called "The Stalker" (based off of The Hidden). The project has gone rather well so far, and I've begun to render, but while rendering I came across a problem. I do have motion blur enabled, and it looks nice and all, but it causes a fast moving object to become transparent? It might be the color, material, or something else.

Motion blur: enter image description here

Without motion blur: enter image description here

It's supposed to look like this (side view): enter image description here

All of the materials are in place, render view isn't restricted, the only difference in any of those images is the fact that Motion Blur is enabled.

  • $\begingroup$ Your object is moving so fast that it has lost its opacity due to motion blur. try reducing the value for motion blur. $\endgroup$
    – user1853
    Jun 23 '16 at 2:56

Motion blurred objects are inherently semi-transparent if they're moving fast enough, because they do not cover any area of the frame for the duration of the exposure. Motion blur results because an object moves during the exposure and thus "partially" covers an area larger than itself. For large or slow moving objects, there will be a large region that they obscure for the entire exposure, thus the transparent blur only appears on the edges. However, if an object is sufficiently small and moving fast enough, it can cover the distance of its own width during a single exposure. At this point, there is no region that is covered for the entire exposure and the object appears to become transparent.

This is not a limitation of CG, it happens with real objects too. See, for example, how the car in this photograph is almost invisible except for the lights which are able to overwhelm objects behind them: enter image description here


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