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Posted on 14/03/22 4:33:45 PM
tom8gem@gmail.com
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Re: Tunnel Shape Interior
DavidMac wrote:
First off I second Steve's comment. It draws you down the tunnel.

You have done a pretty good job of creating the tapered circular effect you wanted for the planking but, on a more technical level, the image does have some issues. To try and make these easily visible I have brightened up the image simply for the purposes of this explanation.

Looking at Image 1 the circular tunnel has three main elements. The left side planking, the ground and tracks and the right side planking. In a classic single vanishing point perspective like this they should all share the same vanishing point.

I have tried to roughly plot the vanishing point of these three elements. It is not very precisely done but is close enough to explain the problem. Image 2 shows the vanishing point implied by the planking of the left and top of the tunnel. Image 3 shows the vanishing point implied by the ground and tracks and Image 4 the vanishing point implied by the boards on the right side. You can see that each element has its own different vanishing point, which should not be the case.

My instincts tell me that the perspectives of No2 and No4 should be adjusted to conform with No3.

Since this is a "synthetic" composite with no real photograph to guide us this has to be a very subjective assumption. However it is quite clear that, as it stands, there are perspective anomalies that need correcting.

I will be curious to hear what Steve and others have to say about this and whether they would assess it differently.




Thank you David; I did have challenges with perspective on this. These will be more complicated to correct; I think I'll wait for others to weigh in before making the attempt.


Posted on 14/03/22 4:33:45 PM
tom8gem@gmail.com
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Posts: 22

Reply
Re: Tunnel Shape Interior
DavidMac wrote:
First off I second Steve's comment. It draws you down the tunnel.

You have done a pretty good job of creating the tapered circular effect you wanted for the planking but, on a more technical level, the image does have some issues. To try and make these easily visible I have brightened up the image simply for the purposes of this explanation.

Looking at Image 1 the circular tunnel has three main elements. The left side planking, the ground and tracks and the right side planking. In a classic single vanishing point perspective like this they should all share the same vanishing point.

I have tried to roughly plot the vanishing point of these three elements. It is not very precisely done but is close enough to explain the problem. Image 2 shows the vanishing point implied by the planking of the left and top of the tunnel. Image 3 shows the vanishing point implied by the ground and tracks and Image 4 the vanishing point implied by the boards on the right side. You can see that each element has its own different vanishing point, which should not be the case.

My instincts tell me that the perspectives of No2 and No4 should be adjusted to conform with No3.

Since this is a "synthetic" composite with no real photograph to guide us this has to be a very subjective assumption. However it is quite clear that, as it stands, there are perspective anomalies that need correcting.

I will be curious to hear what Steve and others have to say about this and whether they would assess it differently.




Thank you David; I did have challenges with perspective on this. These will be more complicated to correct; I think I'll wait for others to weigh in before making the attempt.


Posted on 14/03/22 4:37:47 PM
tom8gem@gmail.com
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Posts: 22

Reply
Re: Tunnel Shape Interior
DavidMac wrote:
First off I second Steve's comment. It draws you down the tunnel.

You have done a pretty good job of creating the tapered circular effect you wanted for the planking but, on a more technical level, the image does have some issues. To try and make these easily visible I have brightened up the image simply for the purposes of this explanation.

Looking at Image 1 the circular tunnel has three main elements. The left side planking, the ground and tracks and the right side planking. In a classic single vanishing point perspective like this they should all share the same vanishing point.

I have tried to roughly plot the vanishing point of these three elements. It is not very precisely done but is close enough to explain the problem. Image 2 shows the vanishing point implied by the planking of the left and top of the tunnel. Image 3 shows the vanishing point implied by the ground and tracks and Image 4 the vanishing point implied by the boards on the right side. You can see that each element has its own different vanishing point, which should not be the case.

My instincts tell me that the perspectives of No2 and No4 should be adjusted to conform with No3.

Since this is a "synthetic" composite with no real photograph to guide us this has to be a very subjective assumption. However it is quite clear that, as it stands, there are perspective anomalies that need correcting.

I will be curious to hear what Steve and others have to say about this and whether they would assess it differently.




Thank you David, I did have challenges with perspective on this one. These will be more difficult to correct (than the lighting issue). I think I'll wait for others to weigh in before making the attempt.



Posted on 14/03/22 6:47:59 PM
DavidMac
Director of Photoshop
Posts: 3932

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Re: Tunnel Shape Interior
Hi again Tom

Once again this is very crude but this is how I believe the perspective should work.

I have very slightly tweaked the ground plane of your image inside the tunnel to make it conform to my grid but I cannot tweak the cylindrical sides and top as the distortions needed are far too extreme. They would need to be re-drawn.

Let's see what others have to say.

Click in the image to enlarge.




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The subtlety and conviction of any Photoshop effect is invariably inversely proportional to the number of knobs on it .......

Posted on 14/03/22 7:20:54 PM
tom8gem@gmail.com
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Posts: 22

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Re: Tunnel Shape Interior
DavidMac wrote:
Hi again Tom

Once again this is very crude but this is how I believe the perspective should work.

I have very slightly tweaked the ground plane of your image inside the tunnel to make it conform to my grid but I cannot tweak the cylindrical sides and top as the distortions needed are far too extreme. They would need to be re-drawn.

Thanks again, David (I can't find where to delete duplicate replies to your earlier post). I thought I'd add this source image to the discussion, as it may help to determine the true perspective.



Let's see what others have to say.

Click in the image to enlarge.









Posted on 14/03/22 9:53:57 PM
tom8gem@gmail.com
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Posts: 22

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Re: Tunnel Shape Interior
(Somehow my reply got mangled. I attached the reference photo and wrote the following):

Thanks again, David (I can't find where to delete duplicate replies to your earlier post). I thought I'd add this source image to the discussion, as it may help to determine the true perspective.


Posted on 15/03/22 11:20:35 AM
DavidMac
Director of Photoshop
Posts: 3932

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Re: Tunnel Shape Interior
Oh Tom!! How I wish you had shown us this photograph sooner.

With any luck it hopefully contains the key to it all.

Watch this space ..................



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The subtlety and conviction of any Photoshop effect is invariably inversely proportional to the number of knobs on it .......

Posted on 15/03/22 12:13:37 PM
DavidMac
Director of Photoshop
Posts: 3932

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Re: Tunnel Shape Interior
Hi again Tom

Your original photo contains the perfect information for determining vanishing points - converging parallels.

The tracks and bottom of the curved walls provide exactly this. If you trace these lines to where they intersect you will define the vanishing point.

All other parallels, such as the joins between the planking, will radiate from this point.

To try and radially distort a photo of planking to fit precisely is possible but not going be easy. I would suggest that you do the best you can with a plain wooden texture without joins which doesn't have to be particularly precise as long as it tapers to the distance. Then draw the joins in black with the line tool on their own layer radiating out from the vanish point. Once drawn use a circular layer mask to hide them where they fall over the rear opening.

Double click the layer to open Layer Effects and apply a slight downward Emboss to give the joints a little depth.

It's actually a lot easier than it sounds ........ and lots of practice with the line tool!

Good luck Tom.

I have to confess to being rather pleased to see that my original guesstimate was very close.



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The subtlety and conviction of any Photoshop effect is invariably inversely proportional to the number of knobs on it .......

Posted on 15/03/22 4:46:27 PM
tom8gem@gmail.com
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Posts: 22

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Re: Tunnel Shape Interior
Thanks so much David, and sorry I didn't post the photo earlier! When I saw what you'd done with perspective lines on my version, it made clear that it was needed; I'd overlooked that.

This is great—I'll definitely give this approach a go! I'd used your (wide version) polar coordinates approach, and as you say, it gets very tricky to get this just right via free transform.

This alternate approach would seem to offer much more control, drawing in slat lines to exactly the angles they need. Also like you say, probably easier too.

So glad this forum is here, I much appreciate your input!

Posted on 15/03/22 6:19:54 PM
DavidMac
Director of Photoshop
Posts: 3932

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Re: Tunnel Shape Interior
It's our pleasure Tom. All of us can remember struggling in the early days.

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The subtlety and conviction of any Photoshop effect is invariably inversely proportional to the number of knobs on it .......

Posted on 18/03/22 11:00:08 PM
tom8gem@gmail.com
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Posts: 22

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Re: Tunnel Shape Interior
And here it is w/ corrections for perspective—thanks a heap, David!

And Gordon as well, and of course Steve!

Hi-res is here, http://thomaskugler.com/img/illustration/darkRides.jpg



Posted on 19/03/22 3:35:55 PM
dwindt
Realism Realiser
Posts: 561

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Re: Tunnel Shape Interior
I saw this last night and read through the discussion. Very good advice guys. I have no idea how I would do this with tricks. I'd slog at it the long tedious way.

I would most probably create a full circle at both ends of the pipe. Starting at top dead center of the first circle, I would section that circle into equal portions...maybe 10 degrees at a time, until I had marked the whole circumference 36 times. (10 into 360 )

I would replicate that circle on the other side of the pipe and resize it. By joining the corresponding 10 degree marks, I would have the perspective for my planks. Then I'd bend and push and skew and bang and cut, until the chaos represents a receding pipe.

n' Boer maak n' plan (a farmer makes a plan) - he uses bailing wire to fix everything that is broken. That's how I use Photoshop...lol...and it works but I'm slow. So my advice to you Tom is, listen to Steve, David, Gordon and the rest because that was sterling advice they've just offered.

Oh, by extending the lines when joining the corresponding 10 degree marks would give you an accurate perspective disappearing view point for your pipe and rail. (Could use only 4 corresponding marks at 90 degree increments) but seeing as I needed guide lines for cramming my planks in convincingly...

but then again, I would most probably use a 3D program cause in this case, it would be quicker.




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Posted on 19/03/22 3:43:02 PM
dwindt
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Re: Tunnel Shape Interior
By the way, I saw your results this morning and couldn't believe I was readying this as an example for you. Very good effort. I'm glad I managed to stay true to your descriptions. Well done.

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Posted on 19/03/22 3:45:00 PM
DavidMac
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Re: Tunnel Shape Interior
Hi Tom. I only just caught your new version. Yes! That works. Excellent. Delighted we have an outcome.

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The subtlety and conviction of any Photoshop effect is invariably inversely proportional to the number of knobs on it .......

Posted on 19/03/22 4:01:57 PM
dwindt
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Posts: 561

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Re: Tunnel Shape Interior
Tom, check your joins between the planks. Especially 10 to 12 'o'clock high. The joining lines must follow the contour of the pipe.

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Posted on 19/03/22 7:07:20 PM
tom8gem@gmail.com
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Posts: 22

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Re: Tunnel Shape Interior
Thanks again, David; your approach worked out wonderfully.

Dennis, I've made slight adjustments to the vertical joins I think you mean. I eyeballed those in; I wasn't sure of a scientific way to get them right. I tried to put each at a right angle across the horizontal plank it divides. At first, I put one on each plank, but quickly decided that was too busy and randomized them to a degree.

Hopefully, this one works better (I've also updated the hi-res version at the URL above). Thank you for your input.







Posted on 19/03/22 10:03:12 PM
dwindt
Realism Realiser
Posts: 561

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Re: Tunnel Shape Interior
Your planks are sitting flush with the pipe surface. Every plank's angle adjusts according to the contour of the surface, (the pipe) therefore the join that you can see across the plank, follows the shape of the surface it is attached to. In this case the plank is attached to a pipe, which is circular so the cut /joint should follow a circular pattern around the pipe, at the point that it is cut.

I hope that the image helps you more than my stammering...lol.



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Posted on 19/03/22 10:35:11 PM
dwindt
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Posts: 561

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Re: Tunnel Shape Interior


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Posted on 24/03/22 04:04:44 AM
tom8gem@gmail.com
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Re: Tunnel Shape Interior
Thank you Dennis, this is very helpful and great to know!

Posted on 25/03/22 08:52:27 AM
dwindt
Realism Realiser
Posts: 561

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Re: Tunnel Shape Interior
You're welcome.

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The grass is greener on the other side of the fence because there is more $hit there.
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