<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">I see. I used the SIGGRAPH 2017 Volume Rendering Course notes as reference, see equation 43:<div class=""><a href="http://graphics.pixar.com/library/ProductionVolumeRendering/paper.pdf" class="">http://graphics.pixar.com/library/ProductionVolumeRendering/paper.pdf</a><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On 25. Jul 2018, at 13:54, Brecht Van Lommel <brechtvanlommel@gmail.com> wrote:</div><div class=""><div dir="ltr" class=""><br class=""><div class="gmail_quote"><div dir="ltr" class="">On Tue, Jul 24, 2018 at 9:05 PM Stefan Werner <<a href="mailto:stewreo@gmail.com" class="">stewreo@gmail.com</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Correct. That’s how we sample every motion effect in Cycles. The trick to get the “smear” is that each camera ray gets a different (pseudo-)random time associated with it (ShaderData::time and Ray::time) and we sample everything at exactly that point in time. Given enough primary rays, the result approaches the integral over the open shutter interval. Adding motion blur should turn one density lookup into one velocity + one density lookup.<br class=""></blockquote><div class=""><br class=""></div><div class="">If we follow the paper it's actually two velocity loops, see formula (7). One velocity lookup works as well, just lower quality I guess.<br class=""></div><br class=""></div></div>
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