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Dave Donley

How Image Props work

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Hi everybody:

Here is how Image Props in VW/RW 10 work:

There are two features of image props that cannot be done with VW 9. One is the automatic transparent color mask generation feature, where a dialog lets you pick a transparent color to use for the mask for the prop. For example if you have an image of a tree and it has a yellow background you can click on one of the yellow pixels and the mask will be generated so that the yellow parts are transparent.

The other is the auto-rotate feature, where the image prop will automatically rotate itself around the z-axis so that is it always facing toward the viewer.

In VW 9 you can create prop objects manually, like this:

1. If you want the object to have a mask, you need to generate a grayscale bitmap where the white pixels are the opaque parts and the black pixels are the transparent part of the mask.

2. Determine the aspect ratio of your source images, ex. an image that is 300 pixels wide and 200 pixels tall has an aspect ratio of (height / width) = 2 / 3.

3. Create a rectangle with the height or width that you want, and use the aspect ratio of the source image to determine the other dimension. For example, if you wanted the width to be 6' then the height of the rectangle should be 6' * (2 / 3) = 4'. Create the rectangle with these dimensions and convert it to a 3D Polygon.

4. Create a new texture, using the source image for an Image Color shader, and using the mask image for a Mask Transparency shader. If you want the object to not be shaded by the lights on your model, set the Reflectivity shader to Constant. A good case for doing this is when you have pictures of trees that have sunlight and shadows already on them.

5. Click the Set By Image... button to set the size of the material to the size of the 3D polygon. If your polygon is 6' tall, then you can adjust the feature size segment so that it is oriented vertically from like the top left to the bottom left corner, and then type in 6' for the dimension. Or if you know the horizontal dimension just type it into the Size field in the Edit Texture dialog.

6. Apply the texture to the 3D polygon. You may have to flip the polygon to get the texture oriented correctly. Textures applied to 3D polygons are oriented so that the first edge of the polygon is the texture's x axis, by default.

7. To see the mask make sure that the RW mode has transparency on if Custom, or use Final as it has transparency turned on.

- or -

1. Upgrade to VW/RW 10, and all this work will be done for you by the Image Prop feature!

p.s. The Image Props can also be resized by the Object Info palette, the texture will resize to fit the object automatically.

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