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Computer Generated Images Combining 3D models with photos, or crafting fully synthetic images using CGI or fractals

Curved motion blur and wheel motion blur

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  #1  
Old 09-18-2014, 06:48 AM
bimbo bimbo is offline
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Location: Orebro, Sweden
Posts: 23
Curved motion blur and wheel motion blur

Hi!

I saw a very cool and well done PP of a Porsche 911 yesterday. Before and after pics here:

https://dl.dropboxusercontent.com/u/...rbo/index.html

The software used for motion blur is called Bleex, www.getbleex.com

I downloaded the trial version and tried it out a little bit. Probably good if you give it a while to get the hang of it.

But my main question is: How was the motion blur of the WHEELS created? I saw a tutorial that basically was:
  • select the wheels
  • copy to a new layer
  • free transform the elliptic wheel into a circle
  • use radial blur
  • free transform back to original shape

That doesn't work very good. I tried it on a photo of my own car, and my car has very deep rims, so it doesn't work.

Any tips for creating wheel motion blur would be very helpful! Thanks!
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Old 09-24-2014, 06:02 AM
John Geoghegan John Geoghegan is offline
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Re: Curved motion blur and wheel motion blur

If you have a photograph of a static car then the method you outlined above is the usual Photoshop method to achieve this effect. However as you discovered it doesn't give great results for a variety of reasons.

The before and after shot of the Porsche is probably a rig shot, in other words the car was in motion when the shot was taken, so the wheel was actually rotating.

Google car rig photography, and you'll find lots of info about how this is achieved.

If the car is a CGI shot then you can get the same result by using motion blur during the render. Basically you select all parts of the wheel which would be moving on a real car and animate them around the axis point of the wheel. So the wheel will be moving during the render and will give a very convincing result.
The only drawback to this approach is that motion blur tends to increase render times quite a bit.

Hope this helps.
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  #3  
Old 09-24-2014, 07:37 AM
bimbo bimbo is offline
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Location: Orebro, Sweden
Posts: 23
Re: Curved motion blur and wheel motion blur

Quote:
Originally Posted by John Geoghegan View Post
If you have a photograph of a static car then the method you outlined above is the usual Photoshop method to achieve this effect. However as you discovered it doesn't give great results for a variety of reasons.

The before and after shot of the Porsche is probably a rig shot, in other words the car was in motion when the shot was taken, so the wheel was actually rotating.

Google car rig photography, and you'll find lots of info about how this is achieved.

If the car is a CGI shot then you can get the same result by using motion blur during the render. Basically you select all parts of the wheel which would be moving on a real car and animate them around the axis point of the wheel. So the wheel will be moving during the render and will give a very convincing result.
The only drawback to this approach is that motion blur tends to increase render times quite a bit.

Hope this helps.
Hi,
I'm well aware of how rig shots are taken. I tried experimenting a little with a Manfrotto Magic Arm, but not with a following car. It's a bit scary though to mount the camera and the arm on an expensive car, you never know if the suction cup might lose its grip :P The "solution" I was looking for is to be able to make a non moving car into a moving one and make it look as realistic as possible

The photographer who shot the Porsche posted the info on Facebook along with this slider, also with links to who had made the motion blur in the background and another guy who made the motion blur on the wheels. In this particular photo though, I suspect that the wheels have been copied from an entire different photo, shot from kind of the same angle. The photo that the wheels were copied from was probably a rig shot. Otherwise he has done a hell of a good job creating the motion blur on the wheels

I also discovered something since I posted this message, namely that there are a few new filters in Photoshop CC 2014, so I upgraded to Photoshop CC 2014. The blur filter gallery has new functions for curved motion blur and radial motion blur. They work ok, but not on all images. If a photo is taken in too much perspective, there simply is no "magic button" to push to create a realistic wheel motion blur effect. It takes several different layers for different parts of the wheel/rim and masking of different parts to make it as realistic as possible.
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  #4  
Old 09-25-2014, 04:06 PM
garnet01 garnet01 is offline
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Join Date: Apr 2008
Posts: 82
Re: Curved motion blur and wheel motion blur

I use Virtual rig, it's pretty expensive but does the job. You just have to break the shot down into loads of different blurs then piece them together.
With the wheels, I've always warped them round then radial blurred them in photoshop.
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