Vtk-js: camera.setParallelProjection(true) issue

Created on 21 Aug 2018 · 13Comments · Source: Kitware/vtk-js

I just need to set camera.setParallelProjection(true), the volume will not be displayed.
Please help me find out what the problem is.
Thanks!!!

released bug 🐞

Source

tanxu1120

Most helpful comment

Update: I made a small codepen that reproduces the "volumes don't render in parallel" problem. https://codepen.io/mix3d/pen/VwwmLvw

My first test with a cone as the input rendered correctly, but specifically with volumeMappers nothing is displayed.

Example of cone object that renders with parallel projection correctly:
https://codepen.io/mix3d/pen/zYYoGLV

Hopefully this helps narrow down the problem.

mix3d on 18 Oct 2019

👍2

All 13 comments

Did you try to reset the camera when in parallel projection?

jourdain on 21 Aug 2018

@jourdain Yes, I did that.However, it still cannot be displayed.

tanxu1120 on 22 Aug 2018

following up on this, we're trying to use parallel projection and it's still not working.

I've tried the above methods, (which were mirrored in an email chain I found somewhere), also tried to played with clipping points and parallelScale, but nothing seems to work.

in one case, I managed to get some things to render, but moving the camera (in a method needed for our MPR approach, moving the focal plane and camera distance together through the volume, with a small clipping plane) results in VERY strange cropping.

Looked through the code, and there doesn't seem to be any unit tests for the camera at all, nor any examples using parallel projection so I'm not totally surprised.

How can we help debug this?

mix3d on 18 Oct 2019

example of strange cropping issue:
perspective progress

The rendered volume slice stays the same dimensions/scale, but moving the camera closer/farther into the volume crops unusually. If I change the camera angle to one not defaulted to a cartesian coord, the clipping becomes even stranger.

removing the setParallel code however, and leaving everything else as-is, renders just fine.

mix3d on 18 Oct 2019

Update: I made a small codepen that reproduces the "volumes don't render in parallel" problem. https://codepen.io/mix3d/pen/VwwmLvw

My first test with a cone as the input rendered correctly, but specifically with volumeMappers nothing is displayed.

Example of cone object that renders with parallel projection correctly:
https://codepen.io/mix3d/pen/zYYoGLV

Hopefully this helps narrow down the problem.

mix3d on 18 Oct 2019

👍2

My "hack" solution for this is to use a camera viewAngle of 1 degree. This approximates a parallel view well enough, but doesn't solve the core problem.

mix3d on 21 Oct 2019

@jourdain @martinken any thoughts / is this on your radar? Perhaps a bug label at least?

mix3d on 21 Oct 2019

I'll try takjng a quick look. Should be a very small fix once I locate the issue.