I follow the offical tutorial chapter 5 “Modifiers and Particle Repopulation in Krakatoa MY” and in the part 2 I trigger the “Force Additive Mode” and add the " repopulate particles" and render but it turns out nothing.please help me out.
Oh, I will go though the steps and see if I can figure out what’s happening.
I think I may understand what you’re seeing.
The particles in this tutorial have no color, and additive renders do not produce an alpha channel. So, it is possible that the particles are being rendered, but cannot be seen because everything is black. Can you try these two things:
- Can you try to render it with a background color? For example, Red. Do the particles appear as black on red?
- If #1 didn’t work, can you also try increasing the “Final pass density” setting? Increasing the density may be needed in your case to see the particles visibly.
Additive rendering with black particles will never produce an image (even with a colored background) since adding black to any other color does nothing.
Ah, Darcy has raised a good point. Additive renders need a non-black “Color” channel.
Instead of setting a background color, Overriding the “Color” channel of the particles to white should produce an image with particles. Does that work for you?
You can override the “Color” channel in the Krakatoa renderer dialog, or by adding a “Set Vector[3]” channel modifier to the particles.
the second part of the chapter 5 is based on the chapter 3.This means that I can render out the particle (already override particle color to blue)in additive mode without repopulations,also I can render it out with all the parameter retained except additive mode off and repopulation on.
With Conrad’s advice, I raise the “final pass exponent” from -1 to 4 and finally I can see the particles,but it’s too grainy,not the smooth and soft feeling (like oil painting or fluid,I really like it) as the tutorial shows.I deem as the tutorial shows,the "final pass dencity"is around 0.5 to get the smooth and soft fluid-alike result,but I don’t know why I just get it blank.
I have discussed this with Bobo, and we’re going to change how the density is computed. Hopefully we can make it easier to use and less grainy.
What happens when you set the repopulation’s “Falloff” parameter to zero? Does that produce a better looking image? It is possible there is a problem with our falloff.
Finally I get the fluid-alike result and maybe ever more better with some param changed.The first time I followed the tutorial and the tutorial didn’t say to set the density to around 5*10^4 so I got it blank.10 hours ago I checked the density but with my carelessness I left the repopulation’s “fill radius” to default 0.1( not as the tutorial said 0.04) so I got the render result too thick and too grainy (I think this is because the size of the particle scene is a bit small and the fill radius set is too big for this particle scene,so far I don’t think it matters very much with the repopulation “falloff”).So I pay attention in these two aspects and get the result right.
Thanks for helping me solve the question, and the density maybe a bit weird when the additive mode and repopulation are both turned on.