Troubles with UV Mapping

[ben_hamburg]

So, I now need to make an oil spillage and need exact UV Coordinates for the shading.
I´m not sure how to do this properly with a phoenix sim I already created.
So far I created a dummy plane to position the UV Coordinates where they need to be in the scene (simple plane mapping, radial gradient map for the mask with tiling turned off.)
Then I copied that UV modifier and simply instanced it over the phoenix sim.
First try it worked, second try it didn´t...
Playing around it first seemd like it only worked if I had "preview" mesh ticked and the phoenix sim selected in the modifier stack.
Then I switched views and again only parts of the ocean extension rendered at all.
Is UV mapping supposed to work like this? What am i doing wrong here?

[ben_hamburg]

Hm, even when it works, it doesn´t seem to work like it should be, mapping takes the grid as reference of course and not the ocean extension. So I guess the only option is do do a seperate pass with vray displaced plane and blend it in post, right?
I wanted to avoid this, because for some reason the vray displaced plane doesn´t line up with the ocean extension, even though I used the same ocean texture in both....

[ben_hamburg]

Update on the ocean tex on the Vraydisplacement modifier: Forgot to set both to vector displacement, now fluid displacement and Vraydisplacement layers are lining up better. There is still some hickups due to the level of detail, so I´ll have to try to either reduce the level of detail in the Vraydisplacement layer (upping the edge length) or putting turbosmooth on top of grid sim to properly blend both layers, right now i´m getting white crest like patterns on the vraydisplacement plane, while the liquid doesn´t have those.
I guess that look is because of the fog settings, so in the vraydisplaced layer the mesh is thinner at the crest, than on the liquid layer it isn´t.

[Ivaylo Katev]

i also noticed the difference between our and vray's displacement and i'm wondering what causes it
actually why you need uv mapping? why not to use world space mapping, as i see it, you have to animate a texture that must represent the oil and to use it for the refractive part of the material.

[ben_hamburg]

Well, I actually never used world space UVs before, so not sure how to achieve what I need this way.
I only need UV mapping so I can specify the part where the Oil spillage is exactly, but I´ll try if I can get there with world space UVs.

I actually think Vraydisplacement ocean looks better, because of the crest like coloration of the water and I´m pretty sure it has got to do something with the triangle count. But then again - I have no clue about the magic goin on under the hood with phoenix...

[Ivaylo Katev]

the vray displacement produces bigger shift in horizontal direction, and this turns the normals downward at the crest, actually it's a bug, but looks good.
you can achieve the same increasing the displacement multiplier in the phoenix displacement section.

[ben_hamburg]

Ah, I see...yeah, sometimes bugs can create interesting solutions. I´ll try to reproduce it with the phoenix grid and see if it blends better this way.
For now we found another quick solution: We simply use a blurred splash pass as a mask to blend the phoenix sim with the vraydisplacement layer, which works pretty well.
Unfortunately I couldn´t achieve what I was after with world space mapping...

[Ivaylo Katev]

can you describe the setup of the oil mapping? how you create the texture that looks like oil?

[ben_hamburg]

I have a 50 square kilometers plane with vray displacement modifier and PhoenixOceanTex on it, UVs with Plane UV Mapping, with gradient ramp set to radial and tiling turned off (broken up by some noise maps with same mapping) to mask the oil spillage around the ship.
The Oil texture itself is just some swirl maps with gradient ramp inside a composite map in the reflection slot and darker diffuse color.
Not sure if World UV works with tiling set to off, can´t get it to work...
Also the Vraydisplacement bug theat looks good from afar doesn´t look so good once the camera gets to close to the surface, so beeing able to do it without extra layer would really help.

[Ivaylo Katev]

i really don't see need to use UV (explicit) mapping in your case, the world mapping easier to use, it also guarantees that all objects in contact have continuous mapping. no need to fit them by hand.
here is my 5 minutes setup, scene and rendering
the size and position of the oil is controlled by the offset/tilling parameter of the gradient map.

[ben_hamburg]

Thanks! I´ll have a look and see what I did wrong!

[ben_hamburg]

No idea what I did wrong, but works perfect now. Might have been because the whole scene was offset from the zero point quite a bit.

[Ivaylo Katev]

yes it's possible that oil spot has been behind the camera.