# Rendering Error / Glitch - How to Fix / Reproduce

**URL:** <https://discourse.processing.org/t/rendering-error-glitch-how-to-fix-reproduce/42297>\
**Category:** Processing\
**Created:** [June 27, 2023, 3:41pm UTC](https://discourse.processing.org/t/rendering-error-glitch-how-to-fix-reproduce/42297 "2023-06-27T15:41:18Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![andrewcooke](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/andrewcooke/32/18406_2.png) [@andrewcooke](https://discourse.processing.org/u/andrewcooke)\
**Post date:** [June 27, 2023, 3:41pm UTC](https://discourse.processing.org/t/rendering-error-glitch-how-to-fix-reproduce/42297/1 "2023-06-27T15:41:18Z")

</div>

Sorry, wasn’t sure what section to post this under. The image fragment below shows bezier curves rendered via P2D with alpha non-unity and blendMode either BLEND or ADD, using processing 4 on Linux w a low spec Radeon card.

![bad-render](https://canada1.discourse-cdn.com/flex036/uploads/processingfoundation1/original/3X/3/6/3605553ccd8a837998550d4b0d763f992cf05ff4.png)

You can probably see that there is some “striping” in some of the lines. This is unintentional and appears to be a glitch in how the image is generated. How do I avoid this and (even better) generate it on purpose?

Thanks,  
Andrew

---

<div class="post-metadata">

**Author:** ![josephh](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/josephh/32/210_2.png) [@josephh](https://discourse.processing.org/u/josephh)\
**Post date:** [June 28, 2023, 1:45pm UTC](https://discourse.processing.org/t/rendering-error-glitch-how-to-fix-reproduce/42297/2 "2023-06-28T13:45:33Z")

</div>

Hi @andrewcooke,

> [@andrewcooke](#):
>
> You can probably see that there is some “striping” in some of the lines.

Actually the image you sent is really small (154x114) in resolution so I can’t really see any issue 😉

Also can you post the code that generates this image? So that we can try it and debug if needed.

---

<div class="post-metadata">

**Author:** ![andrewcooke](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/andrewcooke/32/18406_2.png) [@andrewcooke](https://discourse.processing.org/u/andrewcooke)\
**Post date:** [June 28, 2023, 6:32pm UTC](https://discourse.processing.org/t/rendering-error-glitch-how-to-fix-reproduce/42297/3 "2023-06-28T18:32:35Z")

</div>

the resolution of the image is the same as the original, but if you want to look at more of it, here it is:

 ![17-cmyk](https://canada1.discourse-cdn.com/flex036/uploads/processingfoundation1/original/3X/1/8/18f94ad2ee781b773f676f9bbbdff321a0c123fc.jpeg)

i was hoping it was a known issue.

if you want to run the code, i’ve placed a tarball at [https://acooke.org/sketch\_230623g.tgz](https://acooke.org/sketch_230623g.tgz) - it’s rather complex and i would normally produce a minimal example before reporting a bug (but don’t have time right now - as i said, i was thinking it would be a known issue). that tarball won’t produce an identical image (i don’t know the random seed for the image i used here), but includes an image generated with the current seed (fixed in that code) with the same effect circled in red.