Hello, I am rendering clouds with Krakatoa but my scene scale is larger than life. As a result the clouds don’t look so great. How does one get around this.
Can you post some images perhaps to give a better sense of the issues?
This tutorial shows the general approach Bobo and I were using the last time we did clouds: http://www.thinkboxsoftware.com/krak-clouds-modelling/
The key is to use the “voxel rendering” mode instead of directly rendering your particles so that it smooths the image out and fills in areas between particles.
thanks, I realize my post was a little vauge, sorry for that. I was basically following the methods described in that reference you gave me. The only difference is that the scene scale that I was working in was huge and so the texture and the voxel size was needing to be adjusted accordingly. But it seems that there are other things to adjust as even when I was adjusting these values, voxel size and the texture map size , it was not looking right. Anyway, I thought I was missing another concept or key settings when dealing with scene scale and getting the cloud rendering to work.
as a test, you can make the 100x100x40 unit box in your tutorial and then start scaling up the prt object and you will notice that as you do this it starts to disappear and that’s the issue I am trying to resolve.
Thanks.
Each particle has a Density value. These values are accumulated in a voxel to produce the voxel’s density. If a single particle with Density of 1.0 falls into a voxel with size of 1.0, you get a density of 1.0 in cubic unit.
As you scale an object up while increasing the voxel size, the real-world-units spatial density is reduced. If you scale up an object 10 times, a voxel with volume of 1 cubic unit suddenly turns into a voxel of 10^3 = 1000 cubic units, but it still contains the same single particle with the same Density value. So scaling up 10 times reduces the Density to 1/1000 of its original value. You will either need to increase the Global Density multiplier’s Exponent by 3, or produce 1000 times more particles per voxel to counteract the density loss. If you scale the PRT object up but keep the voxel size, you wouldn’t have enough particles to hit all voxels and the cloud would dissipate into individual voxel islands surrounded by empty voxels.
So in short, the larger the object, the more particles / density is needed.
The same is true in the other direction - if you scale down a PRT object, you have to reduce the Density multiplier to much lower values to avoid very high densities due to many particles in a small space. That’s why we provide the Exponent value in the Density spinners group - by changing it to -1 to -4 with just a few clicks…