<div dir="ltr"><div class="gmail_default"><div class="gmail_default"><font face="monospace, monospace">Hi again to everyone,</font></div><div class="gmail_default"><font face="monospace, monospace">I think that Stefan has nailed the point, the problem in that and, i think, in many other scenes with a lot of light source should be the clamp. In particular, the one that contributes the most at this issue is the "direct clamp".</font></div><div class="gmail_default"><font face="monospace, monospace">As Stefan says, it isn't the "0 Clamp" that produce fireflies, contrarily, the scope of Clamp is to avoid it. But in this particular case, increasing the number of light sources seems to influence the overall intensity of each light.</font></div><div class="gmail_default"><font face="monospace, monospace">However, the most fireflies seems to come from indirect bounces, so I resolved the intensity issues in this scene setting only clamp direct to 0 and leaving the indirect clamp to 4.</font></div><div class="gmail_default"><font face="monospace, monospace">So, I would like to ask, it is reccomended "play" only with indirect clamp, to avoid to lose energy in direct light?</font></div><div class="gmail_default"><font face="monospace, monospace">I'll continue to experiment where and when "direct clamp" is necessary, for the moment I'd like to thanks everybody.</font></div><div class="gmail_default"><font face="monospace, monospace">I'd also like to attach another suggestion posted on the <a href="http://blender.stackexchange.com">blender.stackexchange.com</a> from Zauber Paracelsus yesterday:</font></div><div class="gmail_default"><font face="monospace, monospace"><br></font></div><div class="gmail_default"><font face="monospace, monospace">"The default "Path Tracing" integrator is coded so that for each sample, it will bounce light from a randomly-chosen lamp.</font></div><div class="gmail_default"><font face="monospace, monospace"><br></font></div><div class="gmail_default"><font face="monospace, monospace">My suggestion is that you change the integrator to "Branched Path Trace", which you can change from the Sampling sub-tab.</font></div><div class="gmail_default"><font face="monospace, monospace"><br></font></div><div class="gmail_default"><font face="monospace, monospace">Using Branched PT will make cycles take bounces from every light for each sample. This comes at the cost of increasing render times, but with the added benefit of reducing noise.</font></div><div class="gmail_default"><font face="monospace, monospace"><br></font></div><div class="gmail_default"><font face="monospace, monospace">More info here: <a href="https://docs.blender.org/manual/en/dev/render/cycles/settings/integrator.html">https://docs.blender.org/manual/en/dev/render/cycles/settings/integrator.html</a></font></div><div class="gmail_default"><font face="monospace, monospace"><br></font></div><div class="gmail_default"><font face="monospace, monospace">EDIT: As a further note, Blender 2.79 will feature probablistic termination of lights based on contribution. Basically, it will randomly skip sampling from lights if their contribution to a sample would be below a certain threshold, causing it to spend less time computing bounces for lights which make little or no difference for a given sample. This provides speed gains in complex lighting setups, particularly where some of the lights are distant or occluded. More info here: <a href="https://developer.blender.org/rB26bf230">https://developer.blender.org/rB26bf230</a>"</font></div><div class="gmail_default"><font face="monospace, monospace"><br></font></div><div class="gmail_default"><font face="monospace, monospace">Guido</font></div></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div style="font-size:12.8px"><font face="monospace, monospace"> </font></div></div></div></div></div></div></div></div></div></div></div></div></div></div><div class="gmail_quote">2017-02-13 10:58 GMT+01:00 Stefan Werner <span dir="ltr"><<a href="mailto:stewreo@gmail.com" target="_blank">stewreo@gmail.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span class="gmail-"><br>
> On 13 Feb 2017, at 02:02, F Tamas <<a href="mailto:tamasf.3d@gmail.com">tamasf.3d@gmail.com</a>> wrote:<br>
><br>
> But setting clamp to 0 makes fireflies, so rendertime will be far longer, am I right?<br>
<br>
</span>Setting clamp to 0 does not *make* fireflies. Setting clamp to values other than 0 imposes a maximum brightness limit on individual samples. In many cases, limiting that brightness hides fireflies, but in cases like this, it can take away important contributions.<br>
<br>
A simple case to demonstrate this is if you take an object with a bright and sharp specular highlight and have that reflection be blurred either by depth of field or motion blur. Setting a clamp value on direct light very quickly dims what otherwise is a bright spot/streak.<br>
<br>
With many lights and path tracing, the following situation takes place:<br>
In standard path tracing, only one light is being sampled per pixel sample, all other lights are ignored. To compensate for that, the contribution of that light must be divided by the probability of that light being sampled, that is, divided by the number of lights. With 100 light sources, that means any given light source will be considered for only 1 in 100 pixel samples, but its contribution to that sample will be 100 times that of what it would be if it were just one light source. When that sample is now being clamped, this brightness gets limited and the appears darker than it should be.<br>
<br>
Without looking at the Guido's scene, I cannot tell if this is what’s the issue there, but this is my educated guess.<br>
<span class="gmail-HOEnZb"><font color="#888888"><br>
-Stefan<br>
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