Another way would be to create the gradient fill through Archicad. We have done this in the past and it has worked. Create the fill by drawing a generic arced wall and use a 3D vectoral hatching to show a pattern on the wall in a elevation view. Create a elevation showing the outside of the wall. Open the elevation and select the wall (it will have a gradient pattern applied due to the curve). With the wall selected, copy to the clipboard. From there, create a new symbol fill, paste the image, and scale the settings as needed to show the design. By setting the fill origin and layering the fills, this will give you a gradient effect without using the other programs.
