processing/processing4

Some `shader()` examples behave unexpectedly at higher pixel densities

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#1,063 opened on Apr 25, 2025

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 (16 comments) (2 reactions) (1 assignee)Java (176 forks)auto 404
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Description

Most appropriate sub-area of Processing 4?

OpenGL

Processing version

4.4.3

Operating system

Tested on macOS 13.4

Steps to reproduce this

  1. Open Processing 4.4.3

  2. Run examples in Topics/Shaders (for example Conway);

  3. Notice the rendering is wrong

snippet

n/a

Additional context

Since version 4.4.3, the default pixelDensity is set to match the display's density. During testing, we found that some shader examples break on high-density displays because they implicitly relied on pixelDensity being set to 1.

Some investigation in how shader() is implemented and what assumptions are made there might be needed.

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Contributor guide

Research direction
Investigate the `shader()` function implementation and its interaction with `pixelDensity`. Trace how shader coordinates are set up and why they break when pixel density > 1. Look at the OpenGL rendering pipeline and any assumptions about screen coordinates.
Tech stack
java
Domain
computer graphics
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
JavaShadersOpenGL
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40