How to get world coordinates from UVs?

[magneto]

Hi,

 

I have a model with UVs and I want to arbitrarily sample some UV coordinates within 0-1 space and then get the corresponding world position. I know UVs are not guaranteed to be unique but the UVs I have are.

 

Any ideas on how to do this?

 

 

Thanks

[acey195]

if your object is a square grid, you can just multiply the UV coordinates with (1/bboxSize) in a certain direction. if your object spans the whole world.

if it doesn't span the whole world you would need to use the difference between max and min bboxes compared to the worldsize I guess

[crunch]

Hi,

 

I have a model with UVs and I want to arbitrarily sample some UV coordinates within 0-1 space and then get the corresponding world position. I know UVs are not guaranteed to be unique but the UVs I have are.

 

Any ideas on how to do this?

 

 

Thanks

In the UV unwrapper, you can call uvunwrap().  See the uvlens shader for an example.

 

If this doesn't work, then it's a little trickier.  You might be able to do something with a point cloud (using "uv" instead of "P" for your search attribute).

[magneto]

In the UV unwrapper, you can call uvunwrap().  See the uvlens shader for an example.

 

If this doesn't work, then it's a little trickier.  You might be able to do something with a point cloud (using "uv" instead of "P" for your search attribute).

 

No it's not a grid unfortunately

 

In the UV unwrapper, you can call uvunwrap().  See the uvlens shader for an example.

 

If this doesn't work, then it's a little trickier.  You might be able to do something with a point cloud (using "uv" instead of "P" for your search attribute).

 

That function is for SHOPs, no? I need to do this in SOPs.

[mawi]

In my head this should work...

 

Move the geometry to "uv position" @P = @uv

Use the xyzdist function to get the primnum and paramtric uv at the uv coord.

Now use the primuv function on the original geometry to get world P.

 

I might be able to roll you a .hip later on... 

 

 

vector uvcoord = chv("uvCoord");


int hitid;
vector hituv;


xyzdist(1,uvcoord,hitid,hituv);


@P = primuv(2,"P",hitid,hituv);

Edit.

Something like this might work in a point wrangle if you put...

 

1. a point in input 0

2. The geometry in "uv position" into input 1

3 The original geometry in input 2

 

Cant create a .hip file now, but if you want one I can do that later on tonight...

Edited November 23, 2015 by mawi

[mestela]

Heh, that's exactly what I ended up doing, just came back to find your post explaining my steps while cooking up a hip.

 

Seems like there should be a cleaner way, but this works well enough.

 

uv_lookup.hipnc