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How to use Back To the Center (Basic usage)

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Symmetrically editing object placed with tilt and return it to original location easily.
How to use Back to the Center plugin for Zbrush (Basic usage).
It is described in Ver.1.0.1.
Applied usage and usage of "Change the World-Aaxis" Mode are here.
日本語版はこちら


(Table of contents)


Manual update history

2019/01/28 Manual release


Download

https://gumroad.com/products/yAZUK

This is a donationware. If you think this is a convenient plugin, please donate.

Installation

Finish Zbrush once.

In case Zbrush has been installed in drive C,

place "BackToTheCenter.zsc" to

"C: \ Program Files \ Pixologic \ ZBrush 2018 \ ZStartup \ ZPlugs 64".

After starting Zbrush, start by clicking Plugin> BackToTherCenter> BackToTeCenter.

It is recommended to assign a hot key by CTRL + ALT + click because you will press the button many times.

First prepare material

For example, arrange the demo head with tilt like this.

Since the demo head has subdivision levels, please set it to lowest level 1. in order to understand easily.

(In the image, to show the original location, it represents the shadow of the nonexistent demo head, in fact the eyeballs and teeth are left in their original locations.)
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Find horizontally symmetric vertices

For example here.
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If the gizmo displays, hit the Y key and call a transpose tool and draw the (transpose) action line to these two vertices.
If you make a mistake in selecting two vertices in this step, it will not become symmetrical horizontally in the end.


Holding down the SHIFT + keeping left button pressed and releasing the SHIFT key , you can fix the axis of the camera and rotate the screen, so adjust the camera carefully for easy viewing. Please select two symmetrical vertices carefully.

(I sometimes mistake this, so I recommend rotating the camera view for easy selecting.)

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Run plugin

  • Hot key assignment is recommended, you can assign hot keys with CTRL + ALT + click.

Plugin> Back To the Center> Back To the Center

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Initial dialog (Displayed only first executing)

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I think that this window will come out when you click somewhere.
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When you get out, click the button on the right side (If it does not go out it is OK.)

Save ZPR and back up sub tools etc.

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Please save it for the time being.

Make a backup copy of the sub tool

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Select "Yes" this time.

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Click anywhere.

Entering the subtool name "backup" and press the enter key.

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Then the sub tool was copied and in the non-display state.

Step 1 (Align it to X axis)

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Click "Yes" here.

The object rotates.

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Step 2 (Align it to Z axis)

At this step the object is already symmetrical along to X axis. Please check it as side view with SHIFT + canvas drag.

Next, let the object to rotate so that the direction of the action line you draw in this step is parallel to the Z axis. So, if you make a mistake in selecting two vertices, the object will become look to the sky or the ground.
Still you can edit it symmetrically, but here let's select two vertices to be as level as possible.

Please set side view with SHIFT + canvas drag.
Hold down the SHIFT + pressing left button, and release the SHIFT key and drag to fix the axis of the camera and rotate the screen. It is easy to find 2 vertices like the final location's vertices.

For this time I select two vertices, nose tip and ear hole for easy understanding.

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At this time, the action line is oblique to the left and right when looking from the top but don't worry. At the next rotation, only the angle when viewed from the side is calculated. (that is, the angle with respect to the Z axis direction when rotated around the X axis.)

Let's execute the Plug-in.

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Click "Yes".

Adjustment of upside down

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This time the top and bottom are the opposite, so click "Yes".
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Adjustment of front and back

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Click "Yes" because the front and back are the opposite this time.
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Then the popup window comes out like this.
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Step 3 (Move the object to the origin)

At this step, 3 axes of this object are already aligned to world XYZ axis. Let the center of the object move to the world origin.
You just click the center verticle of the object with the transpose tool.

If you fail to select a center verticle of the symmetrical on X axis here, it will be a waste of your hardships. Please select it carefully and click.

This time, click on the tip of the nose for easy understanding.

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Execute the plugin.

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Click "Yes".

Finally it moved to the origin.

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Symmetric editing is possible

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In this way, because the tip of the nose came to the origin, symmetrical editing became possible. Since the X-axis symmetric brush is automatically turned ON, please confirm that the pointer locations are on horizontally symmetrical vertices.

Well, please sculpt freely. you can take Retoporogy, Zmodeler, Zremesher and Dynamesh. (However, Dynamesh is a deformation that does not guarantee bilateral symmetry, just in case.)

At this time, go next step without sculpt for easy understanding.

Return to the original location

Just run the plugin again.

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Click "Yes".

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It returned to the original location with this.
Just to be sure, let's display the backed up sub tool by clicking the eyeball icon.

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I think that it is almost overlapped. What seems to be slightly off is the effect of mathematical censoring error.
For example, an error of about 0.0001 Zbrush unit is generated with respect to the original location.
(After zooming quite a bit, I moved the Gizmo 3D a little bit and only just confirmed the error, I don't know the exact error by mathmatically.)

So it is not mathematically 100% matches the previous vertices with unedited vertices completely. There are slightly misaligned with each XYZ axis.
Please acknowledge this is a specification at this Plugin.

Why is not it completely returned to its original location?

This is because, for example, one third can not accurately represent with a decimal number.
1/3 = 0.333?
1/3 = 0.3333333?
1/3 = 0.33333333333 ...
None of them are mathematically incorrect.
However, since it handles decimals with PC, it terminates somewhere. So censoring error will occur.
Since this truncation error is included in the calculation of the rotation angle, an error always occurs at the time of rotation. Even if only a single reciprocation and returning to the original location as a result, even a slight censoring error is included. So it will not be the exact same result as sub tool duplication. Please note that this is a PC restriction.

However, since Zbrush is not CAD software, it's difficult to ask for mathematical precision. No one use Zbrush for it, I guess.
So I believe that this Plugin can meet the needs of people saying "It will do as long as it get back to the original location almost nearly perfectly." There may be no need to stick to the error of 1 pixel on the monitor by extreme zooming in, I guess.

The solution is to use "Change the World-Axis" Mode.

In this case the relationship of vertices locations between the objects does not change. Since it is only 0.0001 Zbrush unit shift as the location of the whole object, it will not be a problem. To do that, you will be using te transpose master.
Please note that it takes time and effort to run the transpose master.

The explanation of the basic usage is over. Thank you for reading a huge amount of words.

Applied usage and usage of "Change the World-Aaxis" Mode are here. (in preparation)

FAQ

Sometimes the symmetry shifts somewhat?

It is almost certainly "you failed to select two symmetrical vertices in Step 1". Please press CTRL + Z and the "No" button of the plug-in and return to Step 1 and try again.


Applied usage and usage of "Change the World-Aaxis" Mode are here.

End of document.



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