UV Coordinate Mapped Textures Scale To Different Sizes

[monson67]

I have some materials that I'm creating with images for diffuse textures. I know the exact resolution for each image, and I'm setting the texture DPI to match. When the texture image is applied using Box Mapping, the scale is perfect. When I switch to UV Coordinate mapping, I have to multiply the DPI by 200 to get it to appear correct (from 300 dpi to 60000 dpi). Can anyone explain to me why this happens?

A similar effect happens when I use non-image-based textures, though to a lesser extent. If I select an option from the Texture dropdown, such as Brushed, I have to scale it by 2 when switching from Box Map to UV Coordinate.

Any help would be appreciated.

[guest84672]

UV mapping depends on the scene units you are using.

[soren]

To clarify: only when you check DPI for uv mapping, it is assumed you have laid out your UVs according to the same unit as in the scene.

Note: People rarely do this, but usually unwraps their mesh in the first unit tile in the UV plane (i.e. u,v coordinates between 0 and 1). If you do it like this, no DPI setting is needed (which relates texture pixel size to real world size).

Søren

[monson67]

thomas:
The unit I convert my scene to will change how my Texture Maps scale, correct? As I said before, when converting to UV Coordinate mapping, my Texture Maps immediately scale to 200x their original sizes. So I need to convert to a scene unit near that 200:1 ratio, right?

My scene is currently in Millimeter. If I convert to Centimeter, that's 10:1. Meter is 1000:1. Inch is 25.4:1. And Foot is 304.8:1. Of all of these, converting to feet is the closest I'm going to get, but it still isn't right. 200:304.8 isn't very close, and it's pretty clear, visually, that it's not right.

Søren:
I deselected the DPI option. It doesn't seem to display the Texture Map correctly. It looks like it scales the Texture Map image to fit, or be the same size as, the UV map. How do I know if my UV coordinates are between 0 and 1?

[monson67]

Maybe a better question is — How do I view or edit the UV Map?

I don't even know where to start. Are they only accessible through 3D modeling software?

[Chad Holton]

Maybe a better question is — How do I view or edit the UV Map?

I don't even know where to start. Are they only accessible through 3D modeling software?

That's correct, the UV Map is created with the modeling software (or 3rd party software that specializes in this). If there isn't a UV Map setup for the scene, then you do not want to use this mapping option in KeyShot for most/all cases that I'm aware of.

[monson67]

If there isn't a UV Map setup for the scene, then you do not want to use this mapping option in KeyShot for most/all cases that I'm aware of.

But the only situation in which the material wraps around the model correctly is when UV Coordinate mapping is used. So I would assume that there is a UV Map set up. The problem is that Texture Maps are not to the correct scale.

[Chad Holton]

If there isn't a UV Map setup for the scene, then you do not want to use this mapping option in KeyShot for most/all cases that I'm aware of.

But the only situation in which the material wraps around the model correctly is when UV Coordinate mapping is used. So I would assume that there is a UV Map set up. The problem is that Texture Maps are not to the correct scale.

What modeling software are you using?

[monson67]

What modeling software are you using?

I don't do 3D modeling - just rendering. A coworker uses SolidWorks, though, and I could work with him on this.

[Chad Holton]

I'm not real familiar with SW, so not sure how the mapping is brought over. The way you want to use the UV mapping option though is to actually UV map it in the modeling software first. This way KeyShot knows how to map it when brought in, otherwise it's just guessing.