# Revision history [back]

### How does the population element work?

Looking at the SDFormat spec for v1.8, there is the /world/population element. I'm trying to figure out how this is supposed to work, but I can't seem to find more detailed docs or a usage example. If somebody can clear up my confusion a bit this would be greatly appreciated. What confuses me in particular:

1. If /world/population/distribution/type is set to "random" (a) which distribution is used? and (b) is there a clipping range?
2. The element allows multiple models to be defined. If I specify multiple, how are they used? round-robin? random? only the first?
3. What do the Box and Cylinder elements do? Are they objects that can be spawned as well, or do they constrain the distribution used if type is "random?

### How does the population element work?

Looking at the SDFormat spec for v1.8, there is the /world/population element. I'm trying to figure out how this is supposed to work, but I can't seem to find more detailed docs or a usage example. If somebody can clear up my confusion a bit this would be greatly appreciated. What confuses me in particular:

1. If /world/population/distribution/type is set to "random" (a) which distribution is used? and (b) is there a clipping range?
2. The element allows multiple models to be defined. If I specify multiple, how are they used? round-robin? random? only the first?
3. What do the Box and Cylinder elements do? Are they objects that can be spawned as well, or do they constrain the distribution used if type is "random?

### How does the population element work?work in SDFormat?

Looking at the SDFormat spec for v1.8, there is the /world/population element. I'm trying to figure out how this is supposed to work, but I can't seem to find more detailed docs or a usage example. If somebody can clear up my confusion a bit this would be greatly appreciated. What confuses me in particular:

1. If /world/population/distribution/type is set to "random" (a) which distribution is used? and (b) is there a clipping range?
2. The element allows multiple models to be defined. If I specify multiple, how are they used? round-robin? random? only the first?
3. What do the Box and Cylinder elements do? Are they objects that can be spawned as well, or do they constrain the distribution used if type is "random?"random"?