Rick,
Thanks a million. That works very nicely.
Rob
Rick Towler wrote:
>
> Yes, something as simple as this will work:
>
> zMax = MAX(verts[2,*], MIN = zMin)
> yMax = MAX(verts[1,*], MIN = yMin)
> texCoords = [(verts[2,*] - zMin) / (zMax - zMin), $
> (verts[1,*] - yMin) / (yMax - yMin)]
>
> You'll have to pick the plane you want to project your image onto.
In
> the case above I chose the zy plane. This may or may not be right
for
> you, I didn't really look.
>
> Now, maybe you already know how to do this and you realize that this
> won't apply the texture uniformly across the cylinder and that's why
you
> are posting...
>
> To do that I would create your cylinder orthoginal to the XZ plane
> centered about the origin (you can worry about transforming it
later).
> Then I would calculate the "horizontal" texcoords as a function of
the
> angle of rotation about the Y axis:
>
> yMax = MAX(verts[1,*], MIN = yMin)
> rotAngle = atan(verts[0,*],verts[2,*]) * !RADEG
> cMax = MAX(rotAngle, MIN = cMin)
> texCoords = [(rotAngle - cMin) / (cMax - cMin), $
> (verts[1,*] - yMin) / (yMax - yMin)]
>
> You'll probably have to dress that up a bit.
>
> So here it is all together. Enjoy!
>
> -Rick
>
>
> pro cylindrical_sector
> ; This procedure attempts to create a section of a cylindrical
> ; shell.
>
> ; Use extrusion to create the cylindrical section
> ; First create an arc in the x-y plane
> radius = 1.0 & height = 1.0
> th_lo = 25.0 & th_hi = 180.-th_lo
> n = 50 & dth = (th_hi-th_lo)/(n - 1.0)
> th = th_lo+dth*findgen(n)
> x = radius * cos(!dtor * th)
> z = radius * sin(!dtor * th)
> y = replicate(-0.5*height,n)
>
> type = 5 ; extrusion
> ; Create the array based on x and y
> array = fltarr(3,n)
> for i = 0,n-1 do array[0:2,i] = [x[i],y[i],z[i]]
>
> ; Use MESH_OBJ to create the extruded section
> mesh_obj, type, verts, polys, array, p1=1, p2=[0,1,0]
>
> ; Create a model into which we'll stuff the POLYGON object
> omodel = obj_new('IDLgrModel')
>
> ; Create the image data to be texture-mapped onto the
> ; POLYGON object.
> ;image_data = bytscl(hanning(32,32))
> image_data =
> read_image(filepath('glowing_gas.jpg',subdir=['examples','da ta']))
> help, image_data
> oimage = obj_new('IDLgrImage',image_data)
>
> ; Create the POLYGON object
> osection = obj_new('IDLgrPolygon',verts,style = 2,polygons = polys, $
> color = [255,255,255],texture_map = oimage)
> omodel->add,osection
>
> ; easy method - not quite right
> xMax = MAX(verts[0,*], MIN = xMin)
> yMax = MAX(verts[1,*], MIN = yMin)
> texCoords = [(verts[0,*] - xMin) / (xMax - xMin), $
> (verts[1,*] - yMin) / (yMax - yMin)]
> osection -> SetProperty, texture_coord=texCoords
>
> xobjview,omodel, /block
>
>
> ; better method
> yMax = MAX(verts[1,*], MIN = yMin)
> rotAngle = atan(verts[0,*],verts[2,*]) * !RADEG
> cMax = MAX(rotAngle, MIN = cMin)
> texCoords = [(rotAngle - cMin) / (cMax - cMin), $
> (verts[1,*] - yMin) / (yMax - yMin)]
>
> osection -> SetProperty, texture_coord=texCoords
> xobjview,omodel, /block
>
> obj_destroy, [omodel,oimage]
>
> end
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