VSE: Wrap Width different between preview and render #98482

New Issue

Kevin · 2022-05-29T16:13:05+02:00

Kevin commented

2022-05-29 16:13:05 +02:00

System Information
Operating system: Linux-5.15.0-30-generic 64 Bits
Graphics card: NVIDIA GeForce GTX 650 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 470.86

Blender Version
Broken: 3.2, 3.3 alpha
Worked: 3.0.1

Short description of error
The text doesn't wrap the same way in the VSE preview and in the actual render. This changes randomly depending on the render size

Exact steps for others to reproduce the error
textVSE.blend

I suppose one needs the right mix of text length, Wrap Width, and Font Size for the bug to show up. In my example file, rendering at 50% goes wrong but at 100% it's fine. When I came across this by accident, it was the opposite.

**System Information** Operating system: Linux-5.15.0-30-generic 64 Bits Graphics card: NVIDIA GeForce GTX 650 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 470.86 **Blender Version** Broken: 3.2, 3.3 alpha Worked: 3.0.1 **Short description of error** The text doesn't wrap the same way in the VSE preview and in the actual render. This changes randomly depending on the render size ![Screenshot from 2022-05-29 14-54-46.png](https://archive.blender.org/developer/F13121086/Screenshot_from_2022-05-29_14-54-46.png) ![untitled.jpg](https://archive.blender.org/developer/F13121090/untitled.jpg) **Exact steps for others to reproduce the error** [textVSE.blend](https://archive.blender.org/developer/F13121093/textVSE.blend) I suppose one needs the right mix of text length, Wrap Width, and Font Size for the bug to show up. In my example file, rendering at 50% goes wrong but at 100% it's fine. When I came across this by accident, it was the opposite.

Kevin commented

2022-05-29 16:13:05 +02:00

Added subscriber: @jack.herbert

Pratik Borhade commented

2022-05-29 20:22:13 +02:00

Added subscriber: @PratikPB2123

Richard Antalik commented

2022-05-30 01:27:53 +02:00

Changed status from 'Needs Triage' to: 'Confirmed'

Richard Antalik commented

2022-05-30 01:29:38 +02:00

Added subscriber: @iss

Richard Antalik commented

2022-05-30 01:29:38 +02:00

Could be some inaccuracy in code, because with wrap values different than 0.75 it matches.

tintwotin commented

2022-05-30 10:56:52 +02:00

Added subscriber: @tintwotin

tintwotin commented

2022-05-30 10:56:52 +02:00

Text size is not adjusted to fit when there is a resolution change and Preview is not updated either:

Text size is not adjusted to fit when there is a resolution change and Preview is not updated either: ![res_text.gif](https://archive.blender.org/developer/F13122636/res_text.gif)

Hamdi Ozbayburtlu commented

2022-06-24 14:53:25 +02:00

Added subscriber: @hamdio

Hamdi Ozbayburtlu self-assigned this 2022-06-24 14:53:25 +02:00

Hamdi Ozbayburtlu commented

2022-06-24 14:53:25 +02:00

Yes, I can confirm the inconsistency. After debugging it, I see the preview window is doing the wrap calculation based on unscaled resolution while rendering uses the line width from scaled resolution when I follow the repro steps.
~~So is it better to align preview to render flow and use scaled scene resolution for word wrap or the other way around?~~
But even if the Proxy Render Size is set to Scene Size to have same text wrap result for render and preview window, changing scaling between 50% and 100% generates different wrapping results. This's mostly because of because of having the wrapping calculation in BLF_wordwrap using scaled down integer width value. Investigating if it can be done in a better way.

Yes, I can confirm the inconsistency. After debugging it, I see the preview window is doing the wrap calculation based on unscaled resolution while rendering uses the line width from scaled resolution when I follow the repro steps. ~~So is it better to align preview to render flow and use scaled scene resolution for word wrap or the other way around?~~ But even if the `Proxy Render Size` is set to `Scene Size` to have same text wrap result for render and preview window, changing scaling between `50%` and `100%` generates different wrapping results. This's mostly because of because of having the wrapping calculation in `BLF_wordwrap` using scaled down integer width value. Investigating if it can be done in a better way.

Hamdi Ozbayburtlu removed their assignment 2022-06-28 15:49:34 +02:00

Hamdi Ozbayburtlu commented

2022-06-28 15:49:34 +02:00

Added subscriber: @Harley

Hamdi Ozbayburtlu commented

2022-06-28 15:49:34 +02:00

I've debugged the text wrapping code flow and couldn't find anything wrong with width, height, size values coming into blf_font_wrap_apply from VSE point of view. And at first glance the wrapping calculation seems consistent. I reached out @Harley to understand the root cause. So the possible reason could be:

Wrapping code uses a measure of the string that should only ever overestimate by about the space between a pair of characters (because it includes the space after the last one) so is usually within a couple pixels of perfect.

I'm un-claiming this ticket as I don't have much expertise in font rendering but will keep posting the updates if I hear/find more.

I've debugged the text wrapping code flow and couldn't find anything wrong with width, height, size values coming into `blf_font_wrap_apply` from VSE point of view. And at first glance the wrapping calculation seems consistent. I reached out @Harley to understand the root cause. So the possible reason could be: > Wrapping code uses a measure of the string that should only ever overestimate by about the space between a pair of characters (because it includes the space after the last one) so is usually within a couple pixels of perfect. I'm un-claiming this ticket as I don't have much expertise in font rendering but will keep posting the updates if I hear/find more.

Philipp Oeser removed the

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VSE: Wrap Width different between preview and render #98482