[Feat]: Outline geometry

[barvirm]

What is your idea?

Would it be possible to generate outline geometry?

WebIFC has the same output as OpenIFC Viewer

OpenIFC Viewer:

BIMvision:

BIMCollab

[thbeu]

Can you please attach your IFC file here. Thanks. For the background: I already added "Outline Geometry" to IfcViewer which is based on engine_web-ifc and want to compare.

[mezlondr]

It is of course possible, but as far as I know it requires a bit of work. I'm simply processing faces of every mesh and generating edges based on sufficiently sharp angles between them. Another option is with shaders but in my opinion that does not yield as good results as that rather resembles a highlight.

[barvirm]

@mezlondr Algorithm that you propose wouldn't get these type of outlines:

[barvirm]

@thbeu I cannot share the model publicly, but i made another model for you.

Here is zip with the model, github doesn't allow to share .ifc files.
ifc_outlines.zip

Bim Vision

WebIFC

[mezlondr]

It would, since the model is composed of multiple meshes, each having its outline. My algorithm on your ifc:

@mezlondr Algorithm that you propose wouldn't get these type of outlines:

[thbeu]

IfcViewer

[avlsoraj]

It would, since the model is composed of multiple meshes, each having its outline. My algorithm on your ifc:

> [@mezlondr](https://github.com/mezlondr) Algorithm that you propose wouldn't get these type of outlines:

Hi, you can generate outlines based on object IDs and surface normals. This screen-space approach works well in some scenarios, but it does not cover cases where you need to render hidden lines or simply display the entire scene in outline mode.

For these scenarios, it would be useful to have the outlines generated directly by WebIFC, ideally from the underlying IFC topology/geometry rather than from the rendered image. WebIFC already exposes the generated vertex and index geometry, so exposing the corresponding edge information would make it possible to handle these cases more reliably.

thx J

[mezlondr]

It would, since the model is composed of multiple meshes, each having its outline. My algorithm on your ifc:

[@mezlondr](https://github.com/mezlondr) Algorithm that you propose wouldn't get these type of outlines:

Hi, you can generate outlines based on object IDs and surface normals. This screen-space approach works well in some scenarios, but it does not cover cases where you need to render hidden lines or simply display the entire scene in outline mode.

For these scenarios, it would be useful to have the outlines generated directly by WebIFC, ideally from the underlying IFC topology/geometry rather than from the rendered image. WebIFC already exposes the generated vertex and index geometry, so exposing the corresponding edge information would make it possible to handle these cases more reliably.

thx J

Note that the algorithm I'm proposing does not work with screen space at all, but with the geometry in world space, so you can have entire outline without drawing a single mesh. I have not found a case yet where this approach would not work well.