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vdamjanovski

[By Design] Perspective tool bug

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I believe there is a bug with the Perspective tool. 

I use both Designer and Photo since its inception, and I am happy with what I can do with them, although there are some limitations, and the first one that I need it fixed is the perspective tool Here is what I have found:

I am trying to design a Siemens Star, for the purpose of producing our test chart. Since it is not possible to create a triangle which changes the gradation from white to black proportional to the distance from the centre, I thought I found a way to create first just simple vertical strips with linear gradation, one half on the left peaking in 100% black colour, and the other half on the right peaking to 100% white (please refer to the attached screen-shots for better understanding).

From there, it should be straight forward job to use the Perspective tool at the bottom of the rectangular strips and marge them to the bottom centre. It all goes good until I touch the two ends, left and right, in the middle. The whole image then disappears and only the mesh stays to indicate the required perspective.

Where do the graded stripes disappear (image stage 4)???

Is there any other way I can create  section of sine wave "pizza-slice" with continuous gradation proportional to the edges of the triangles??? 

P.S. Working on our test chart, I have also found, this time in Designer, that the black level intensity (when measured with the pick tool) is inconsistent with the RGB pick tool. For example, if using 8-bit colours, the 10% white (90% black) when measuring in RGB mode,  should measure 25 binary units of each primary colours (R, G and B), but this is not the case. If I make a rectangle with 25 binary units of R, G and B, the Grey level pick tool measures 12 units of white, instead of 10. Similarly, the RGB of 50, measures 21 units of white, further intensities of white, get converted correctly, so the very low end of white (high end of black) when measured with the pick tool in Grey mode is incorrect relative to its RGB pick tool measurements.

Perspective tool stage 1.png

Starting point for a Siemens star unit slice.png

Perspective tool stage 2.png

Perspective tool stage 3.png

Perspective tool stage 4 - the strips dissapeared.png

Siemens star final.png

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1 hour ago, vdamjanovski said:

I am trying to design a Siemens Star, for the purpose of producing our test chart.

From your description I don't think you are making a Siemens Star. I also don't know what you would be able to test with the design on the bottom, certainly not resolution which is what I have had to use those things for.

Black and White, no grey.


MacBook Pro (13-inch, Mid 2012) Mac OS 10.12.6 || Mac Pro (Late 2013) Mac OS 10.14.5

Affinity Designer 1.7.3 | Affinity Photo 1.7.3 | Affinity Publisher 1.7.3 | Affinity Designer Beta 1.8.0.2 | Affinity Photo Beta 1.8.0.163 | Affinity Publisher Beta 1.8.0.536

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15 minutes ago, Old Bruce said:

From your description I don't think you are making a Siemens Star. I also don't know what you would be able to test with the design on the bottom, certainly not resolution which is what I have had to use those things for.

Black and White, no grey.

Sorry Old Bruce, that was in the old days.

The new standards are with sine wave stars, which is why I am doing this.

I hoped you will address the problem of perspective, if you know the reason for the issue.

Thanks anyway.

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Hi both,

This is by design. You need 4 different points to create perspective. If 2 points are identical, the perspective is infinite and it won't display. The best practice would be to leave 1px distance between the 2 points, or 2 pixels if you want them to be equally distant from the centre.

image.png

Thanks,

Gabe. 

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Thank you Gabe, I already figured this out, and created a new Siemens star with 144 stars. Quite a task, as I wanted some precision, and the angles are not precise enough to align them, but anyway I did it, and thank you again.

What about the P.S. question? Any comment on the error in Gray and RGB colour spaces?

Thanks.

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On 5/30/2019 at 2:28 AM, vdamjanovski said:

if using 8-bit colours, the 10% white (90% black) when measuring in RGB mode,  should measure 25 binary units of each primary colours (R, G and B)

Not really. 10% should show a value of 26 (25.6 rounded up to the nearest integer value). However, this shows a value of 19, which I will log for further investigations. 

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The greyscale readout is doing a profiled ICC conversion from whatever your RGB profile is to whatever your default greyscale profile was at the time of document creation.

It's likely the greyscale profile and RGB profile have different white points or gamma ramps.

This would be by design - but we have no way to change these profiles after document creation, which should be logged as an improvement.

Thanks,

A

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Thank you Andy, that is a nice explanation.

I created all my work in the Designer, from scratch, and to be honest I never paid attention to the choices of the many grey colour spaces you have.

I design colour test charts for CCTV, which I print on professional A2 size Epson ink-jet. In the test chart I have 11-steps grey scale, which goes from black to white in increments of 10%. I expect that the 10-percent increase in whiteness, as seen on the Designer screen, is reproduced in equal steps when printed, but this is not the case. 

I do understand the different colour spaces between screen and print, and I even have an old Spyder colour calibration tool. 

Which of the grey colour spaces should I use to match the equal steps of the print to my screen colour picker measurement (Generic Grey, Generic Grey Gamma 2.2, D50, Epson Gamma 1.8, Epson Gamma 2.2,...)?

Is there any manual or knowledge based document that explains the differences? As I couldn't find anything under the Help. 

Thank you again for your time.

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