Varying Rock Sizes

[Nova1021]

Hi folks! I'm new to Terragen but am gradually figuring it out. I'm trying to create realistic renders of Mars, and am running into some confusion with rocks. Is there any way to control the size-frequency distribution of rocks? for example, make 80% of rocks between 1 and 10 cm, 15% of rocks 10 cm to 1m and 5 % of rocks >1m in size?

I thought maybe multiple fake rock shaders would do it, but I cant figure out how to do multiple rock shaders and also apply surface textures, etc to them.

A related question is: is there a good way to make rock sizes vary with distance? I'f like to make a crater with ejecta around it, and to be realistic, the ejecta should start with large blocks near the crater rim and gradually get small with distance from the crater.

Any ideas would be great. Thanks!

[inkydigit]

hi there,
welcome to the forum!
try here:

http://forums.planetside.co.uk/index.php?topic=3796.msg41840#msg41840

use layers of fake stones (I start with the largest) set the stone density to your requirements for each size, and use the merge shader set up listed above...

[Nova1021]

Thanks for the tip! It looks like "merge shaders" was what I needed. Here's my Mars scene so far...

[inkydigit]

looking good, as for the scale and distance, use distance shaders; set a new camera at the centre of your crater, use this as your anchor for the different distance shaders, using these as your blend/density for the fake stones...

[Nova1021]

Thanks! I figured out the distance shader trick this morning. Now the question is, how would I go about making the density of ejecta stones vary around the crater? Real craters have "rays" of ejecta emanating from the crater rather than a uniform spread of stones. (For example: http://hirise.lpl.arizona.edu/images/2008/details/cut/PSP_008011_1975_cut.jpg)

I also need to figure out how to make small dunes in the crater and near stones. I've searched around the forums for some of the dune discussions, but haven't come across anything that looks quite right yet...

While I'm at it: is there a way to make a population of craters of varying sizes? Or will I need to make them one by one?

[Dune]

http://forums.planetside.co.uk/index.php?topic=7327.0