Primuv() Vex Function

[Guest xionmark]

Hi,

I'm trying to use the primuv() function but am getting an error that I do not understand:

Here's the function prototype:

float primuv (string SOP, float prim_num, string attrib_name, float attrib_index, float u, float v)

Here's a code fragment using the example from the VEX help page:

pop myPOP_Color ()
{
float grn;

grn = primuv("/obj/geo1/tube1", 0, "Cd", 1, 0.7, 0.3);

}

When compiled I get the following error:

> vcc myPOP_Color.vfl
"myPOP_Color.vfl" line 7 ERROR (1041) A value type of "void" cannot be assigned
grn = primuv("/obj/geo1/tube1", 0, "Cd", 1, 0.7, 0.3);

                                                      ^
WARNING (2007) Variable "grn" was declared but never used
REMARK (3002) There is 1 unused variable
REMARK (3003) 1 error and 0 warnings encountered
REMARK (3007) No output is generated due to errors in the source code

Is vcc really complaining about trying to assign to a var of type void? Because it shouldn't be trying to assign a value to any parameter of the function call. The error message is confusing me ...

--Mark

P.S. Here's the VEX help page for primuv():

float primuv (string SOP, float prim_num, string attrib_name, float attrib_index, float u, float v)

Evaluates the specified attribute at a parametric (u,v) position on

the primitive. u and v are unit values, defined in the [0,1]

interval. When given the "P" or "Pw" attribute, the x, y, or z

image of the (u,v) domain point will be returned. If the primitive

is a face type or a circle, v is ignored.

NOTE: if the primitive is a polygon or a mesh, u and v are defined

in terms of the number of vertices, or rows or columns

respectively. Currently, only the positional attribute of quadric

primitives can be evaluated.

For example: primuv("/obj/geo1/tube1", 0, "Cd", 1, 0.7, 0.3) Will

evaluate the Green component of the diffuse color attribute at a

location on primitive 0 given by the parametric coordinates

(0.7,0.3).

[sibarrick]

I'm a bit confused, primuv isn't a vex function AFAIK. Its a standard houdini expression. The closest thing in vex is prim_attribute. Where is the vex help page that you got this from?

[Guest xionmark]

I'm a bit confused, primuv isn't a vex function AFAIK. Its a standard houdini expression. The closest thing in vex is prim_attribute. Where is the vex help page that you got this from?

17905[/snapback]

Yep, you're right! I'm wondering why vcc didn't say something like "unknown function"?

I'll try to use the prim_attribute call 'cause I'd like to do this in VEX, I think it'll do the same as the primuv expression.

Thanks!

--Mark