Here is the final product created in Photoshop.
This tutorial will skip through the package designing aspect. I'll assume the box is already designed as it will print and assemble. To start, here is the PET box I designed, laid out flat and disassembled.
In Illustrator, where the box was designed, I can choose to export the sides I need. We'll need the left, right, top, and bottom sides. Those are all on the left side. You'll also need the back, obviously. Illustrator actually has slices so you can go in and precisely cut out those sections.
Now in Photoshop, create a new document. Since this package is measured in inches, i would be better if the new document size could contain those inches without sizing. That is why I'm choosing 11x17 inches. Resolution can be 72 since this doesn't have to be very high-res.
Select the Rectangle Tool (U). Click the arrow beside the custom shape icon.
With the shape layer selected, pop open the 3D Repousee panel. Choose 3D Repousee Object with source at Selected Layer.
Side's width / face's width
So on this box, I would divide 0.75 by 4. This is 0.1875. Under Depth, type in .1875. Now the box's depth should appear more accurate.
The 3D Repousee panel should now show the materials on the shape. These will be textured to give the box its final appearance.
Now since the front face is already selected, click on the icon next to Diffuse. Select Load Texture and find the correct image.
When the texture loads, you'll notice this.
Now turn the box around so the back can be seen. In the 3D panel, select Back Inflation. Just like before, load the proper texture and enter the same Texture Property values as before. However, this time the texture is flipped incorrectly. Back in the drop menu, choose Open Texture. This opens the texture for editing. Go to Image > Image Rotation > Flip Canvas Horizontal. Save and Close that document (Ctrl+S, Ctrl+W) when you're done. The texture should appear correctly on the back.
This step is very important so make sure you follow the directions exactly. The files will be placed in scale mode, so make sure there is no scaling and they're at 100%. Also make sure you have Smart Guides enabled to align the pieces together precisely. On the left and right side textures (the vertical textures), rotate them 90 degrees counterclockwise. This should create a texture strip. Arrange the texture strip in the following order: bottom, left side, top, right side.
It should look something like this by now. When you've gotten this far, Trim it (Image > Trim), letting it cut out transparent pixels. Finally, go to Image > Image Rotation > Flip Vertical for the final rotation. Save this image and place it in the folder with the other images.
Quick Fix: Both side textures should actually look the same at this step.
Back to the 3D render, select Extrusion Materials from the 3D panel. Load the newly-created texture via Load Texture. And it doesn't texture properly.
This is the biggest problem of the entire process because in the 3D Repousee window, the texture actually renders correctly (besides the vertical flip which is part of the solution) and outside of that, it renders completely differently.
Pixel Height / Extrusion Amount + Pixel Height
On this box, it would be 54 divided by 0.187 and + 54. I get about 342 pixels. Enter that as thew new height and check up on the 3D box. I got this.
Fortunately, that's the last step! You can reposition the box in any number of ways and ray trace a great looking final render with a realistic shadow.
The final image once again.
You can download the source files. It includes the textures used and the PSD file for this project. You'll need Photoshop CS5 and higher to open.
Update: * Since the texturing formula doesn't always work, try this for more consistent results. Take the sides texture and arrange it as correctly described. Make the document's height the same as width, so there is much more blank space below. Back in the 3D model, go to "Edit Properties" for the texture and play around with V Scale and V Offset. One of the multiples of 25 should get the texture to appear with no distortion. Sometimes V Offset is needed to align it properly, but it will also be a number related to the Scale value.
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Please don't repost this without letting me know first. Contact me at firstname.lastname@example.org for related topics.