CesiumGS/cesium

Non-normalized AlignedAxis Is Ignored

Open

#6,596 opened on May 17, 2018

View on GitHub
 (4 comments) (0 reactions) (0 assignees)JavaScript (11,758 stars) (3,324 forks)batch import
JTCgood first issuetype - enhancement

Description

The Billboard documentation states that "The aligned axis is the unit vector that the billboard up vector points towards. The default is the zero vector, which means the billboard is aligned to the screen up vector." This indicates that the aligned axis should be a unit vector.

However, if you give the Billboard a non-normalized "unit" vector, that vector is completely ignored and the default is used instead. I think that either: A) The documentation should clearly state that any non-normalized alignedAxis will be ignored and replaced with the Zero vector. or better yet, B) The alignedAxis should not have to be normalized in the first place. The Cesium code can normalize the axis internally if it needs to.

Contributor guide

Tech stack
javascript
Domain
frontend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
JavaScriptCesium basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
The issue is about the Billboard alignedAxis ignoring non normalized vectors. The fix is either to update the documentation (e.g., in the Billboard.js source comments or the official docs) to state that non normalized vectors are ignored, or to normalize the axis internally. Look at the Billboard class in Source/Scene/Billboard.js to see how alignedAxis is used. If choosing the code fix, add normalization in the setter or update logic. If choosing documentation, find the relevant doc strings and update them. The issue comments may provide additional context.