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Alex W

Scaling a 360 degree sky texture to a sphere

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Hello people,

We are having enormous difficulty doing an incredibly simple task here in our office.

We ar etrying to create a sky dome for our model.

We have a 360 degree sky texture. We have a sphere object (with the mid circumference set at horizon level).

We cannot figure out how to get the texture to map correctly to the sphere, there appears to be no option to set the texture size to the same size as the image (we have no way of knowing what 'real world' size to use for our texture).

We then need the texture to start half way up the sphere (i.e. at the horizon line)

This should be very simple, are we being a bit thick here?

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Not so simple a mapping problem ... spheric surfaces are faceted>see the SphereTool polygon mesh at various resolutions.

If you require exact mapping then NURBS gores work best.

There's a really great app > Flexify> www.flamingpear.com which handles the image mapping procedure.Then you will need to use VW to create the Gores based on the mapping ( hint> use Revolve with Rail : )

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Thanks for your reply.

We were able to get the texture to sucessfully wrap around the inside of the sphere, it automatically uses a spherical mapping solution, and seems to do a fairly good job.

Our main problem was that there was no way to set the texture scale to use just one instance of the image for the entire map, i.e. the texture would be tiled once, and stretch to fit the entire area of the mapping, VW's appears to have no option other than real world size for choosing how textures tile. I had thought that this was a fairly basic requirement of texture mapping, but I may be wrong...

Hopefully this makes sense.

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under object info, render tab you normally have a scale slider. no? i mess with this in Open GL until i get what i like or if even that takes too long i edit just the object itslf with a rigt click adn go into Open GL and mess with that scale. I find that the scale can get greyed out when using a stock texture that is designed to be continuous as opposed to repeat. Is theis the problem?

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Yes, than kyou this is the exact problem.. this is what in 3D terms is usually called "real world scaling" of a texture, i.e you set the actual real world size of the image to be used for the texture, and it then repeats according to the size of the object. As well as this, most 3D apps will have an option to specify how many times the texture image repeats regardless of what size the object to be mapped to is.

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...oops, didn't finish the post...

what I was wondering is if there was this option in VW/RW.

We have tried 'messing around' with the texture scale and the object size and found it to give an unsatisfacorary result; no matter how hard we try it won't line up perfectly, and there is always an anomoly where the texture edges meet.

Oh just re-read your post... sorry no, the problem is not that the scale is greyed out, the problem is that it seems to be the only way of choosing how the texture is repeated.

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