Hello, hope my question is not too overasked or outdated.

Im currently using H14, and i am following a tutorial on procedural grass. However, the tutor is on H13, and there is a point whereby I could not go on due to slight differences in the VOPs.

tutorial link : https://www.sidefx.com/index.php?option=com_content&task=view&id=2488&Itemid=383 [sidefx.com]


Go to 29:06 (end at 35:13) I could not get this area working

To summarise : there are a few VOPs like import attribute and add attribute. the global VOPs also seem a bit different. Please help ><

P.S. : i am still a student, might need precise guidance on steps ><. sincere thanks!

(object needed help with is the object labelled “grass” on the scene level)

I think the biggest difference about expressions between 15 and 14 is that you can't use “$+attribute name” to transfer local attribute between different nodes. Not only for those attributes added by yourself, you also cannot use local attribute such as $CY outside the copy node. They are indeed LOCAL in the new version.

Try to use @ operator instead, but unfortunately I found they sometimes doesn't work…

There are three ways that transfer local attributes from one node to another I think may work. One is to use channel expression to reference the value on the interface.

eg. ch(“surface_node/channel name”).

The second one is to use function to “read” attributes from points or primitives,

eg. points(surface_node, point_number, attrib_name, attrib_index)
or, primuv(surface_node, prim_num, attrib_name, attrib_index, u, v)

The third one is to use Bind or Parameter node, and gave them a same name to the attribute you want to cite in Attribute Vop node.