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Can I extract shadows using only Vectorworks


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I have Vectorworks v10.1.2 including Renderworks running on the Mac OS9 platform. I have supperimposed my design on an appropriate imported background and rendered it using the final quality option.

Looks good apart from there being no ground shadows. Can I create a temporary or transparent 3D polygon to simulate the ground, cast the shadows onto it and then extract them, or superimpose them onto my final rendering. I do not have access to any other graphics software therfore it must all be achieved within Vectorworks.


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  • Vectorworks, Inc Employee

Hello AJLister:

Yes, this is possible to do. The results may or may not be satisfactory for you, though:

The idea is that you create an image prop from a top rendering of your model, with shadows. The top rendered image will be used to create an image prop 3D polygon. The non-shadow parts of the top rendering would be the transparent parts of the prop mask, and the shadows would be opaque. You place the prop on the ground under your model lined up properly, and render with transparency turned on. The mask of the prop would make the shadow areas opaque and the rest of the ground plane transparent, showing the background.

In some detail:

1. Place a 3D polygon under your model, making a note of its dimensions. Set its color to the overall hue that will match the ground under your model. For example, if your background uses sand as the ground, color the polygon tan.

2. Set the view to top orthogonal. Set the Custom RenderWorks options so that shadows are on. Use the Render Bitmap Tool to draw a marqueed area matching the corners of your 3D polygon.

3. Using Export Image File, draw a marquee around the rendered bitmap, exporting it using TIFF.

4. Create an image prop with the same dimensions as your 3D polygon, using the exported image as the source for the prop. Click Use Mask. Choose to use a transparent color for the mask. Use the prop's color for the mask.

5. Select a non-shadowed pixel to set the transparent color for the mask.

6. Choose to not create a plugin object, and not to use Constant Reflectivity for the prop. Click OK.

7. Rotate the 3D polygon created 90 from vertical and place it in the same location as your ground plane 3D polygon. Delete or otherwise hide the 3D ground plane polygon.

8. Render using transparency, and you should see the background and the shadows should appear opaque.

If you had access to even a simple bitmap editing app, you could make partially transparent shadows by tweaking th top rendered image so that the shadows are a bright gray and the non-shadowed areas are black. The black areas of the mask are completely transparent, and the gray areas would be partially transparent (white is completely opaque).

Here's a very gross example. I didn't match the background image color on the shadows, the alignment is off, etc.:



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