Pattern generator ?

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davidh
Posts: 835
Joined: June 9th, 2009, 2:16 am

Pattern generator ?

Post by davidh »

I wanted to create a custom halftone screen from tiny squares. So I used the Checkerboard transformation, but since there is no setting for the square size, I resized the checkerboard output a tiled it. It came out quite well, but there are visible lines from the tiling. Only slightly but visible.
I realize that the Checkerboard transformation has other purposes, still, a generator of regular patters of squares, dots, diamonds, crosses, etc. would fit nicely into the current transformation collection sometimes in the future.
jsachs
Posts: 4203
Joined: January 22nd, 2009, 11:03 pm

Re: Pattern generator ?

Post by jsachs »

You can specify the square size in Checkerboard - it is listed as "patch width" which is probably a poor choice on my part.

A number of the patterns you mention are available in the Picture Window Pro folder under Textures\Dots. They can be tiled to make larger image as necessary.
Jonathan Sachs
Digital Light & Color
davidh
Posts: 835
Joined: June 9th, 2009, 2:16 am

Re: Pattern generator ?

Post by davidh »

Yes, but it is the patch width. The maximum size of the output is 512 x 512. So it still needs to be tiled. Either using Tile transformation or automatically inside the Halftone transformation.
The thing is that the effect is different if you start with a big checkerboard (e.g. 20000x 20000) with big squares and resize it and tile one or two times.
I cannot explain why, but starting with big checkerboard gives better results.
Anyway, it is not important I am just exploring possibilities. Thanks for the tips.


Talking about resizing and halftoning:

If you change a resize width and/or height and click OK too fast, the dimensions of the output will not change, or at least the preview is not refreshed, but the new value is still saved. If you then reload it form a script, the image preview shows the right dimensions. If you save the image and reopen it also has the right dimensions.

Load a screen to the Halftone Screen Control and leave the dialog.
Close the screen -> this does not close the Halftone thumbnail, but the Halftone Screen Control then does not show any items. They are there but not visible. You can click somewhere into the list and load one.
jsachs
Posts: 4203
Joined: January 22nd, 2009, 11:03 pm

Re: Pattern generator ?

Post by jsachs »

Patch Width is the size of each square of the checkerboard in pixels (2 .. 10000) - the total output image size in pixels is the number of columns/rows times the cell size. Since you can have up to 256 columns or rows (which I am increasing to 1000) you can currently generate an image up to 2560000 x 2560000 pixels.

In general, you should tile before resizing to avoid artifacts, since the checkerboard tiles are seamless but resized ones may be very slightly off.

There is a 2 second delay before responding to keyboard input to allow you to input multiple digits without updating the preview after each one. When you click OK or Apply, any pending keyboard input is processed first, so this is normal behavior.

Interesting note about closing the custom screen -- you are not supposed to be able to close an image that is currently in use so I need to see why it is being allowed.
Jonathan Sachs
Digital Light & Color
davidh
Posts: 835
Joined: June 9th, 2009, 2:16 am

Re: Pattern generator ?

Post by davidh »

"...Interesting note about closing the custom screen -- you are not supposed to be able to close an image that is currently in use so I need to see why it is being allowed....."

The custom texture still can be closed while the dialog is open, however now it gets removed from the Custom screen control. Moreover, according to what says the closing button on the Close file box, the Halftone image is dependent on the screen and therefore should be closed too, but it is not.

One more remark on dependecies:
If you add a side branch to an image and then click the close buton on the empty branch box, you get two options to select from: Cancel or Close the current branch and all other images that depend on it. But there are no dependent images.
Though not of a big importance, this might a bit confusing, because when you try to close an image, not a branch box, the system recognizes whether something depends on it. And if there is no dependecy, it offers the shorter option: Close the current image instead. Then you know that the system knows.
jsachs
Posts: 4203
Joined: January 22nd, 2009, 11:03 pm

Re: Pattern generator ?

Post by jsachs »

Fixed for next release
Jonathan Sachs
Digital Light & Color
jsachs
Posts: 4203
Joined: January 22nd, 2009, 11:03 pm

Re: Pattern generator ?

Post by jsachs »

A good halftone screen has an even distribution of different gray levels in each cell, so Checkerboard is not a good tool to create a custom halftone screen. For small cell sizes, they are usually made by hand or by some algorithm - for large cell sizes you can use the Equalize transformation to force an even distribution of gray levels.
Jonathan Sachs
Digital Light & Color
davidh
Posts: 835
Joined: June 9th, 2009, 2:16 am

Re: Pattern generator ?

Post by davidh »

I was exploring different effects of various screens starting from the downloaded Mezzotint textures to my own experimenting with Textures. I also tried to simulate the orderly effect of Classical or Ordered inbuilt screens so I played a bit with the checkerboard. I did not finish just with the plain B+W squares. I used Brightness Curve to reduce the contrast with Composite Shift Alignment, and at some settings the result was not completely useless with the right images. I also tried Edge, Blur and even Watercolor. Some of the textures generated quite interesting effects, though not much applicable. :) A game of trial and error.

I have not use Equalize for this purpose yet, so thanks for the tip.
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