GLSL: Cleanup Clip Space vs. NDC Space naming #105070

New Issue

Clément Foucault · 2023-02-22T13:26:02+01:00

Clément Foucault commented

2023-02-22 13:26:02 +01:00

Throughout the GLSL codebase Clip Space and NDC Space are both refereed using the same prefix ndc_.

But they aren't the same thing:

Clip space is what comes out of the projection matrix multiplication (i.e:vec4 clip_point = winmat * vec4(vs_point, 1.0) or more commonly vec4 clip_point = point_world_to_ndc(vs_point))
NDC (Normalized Device Coordinate) is the result of the perspective division (i.e: vec3 ndc_point = clip_point.xyz / clip_point.w or more commonly vec3 ndc_point = project_point(winmat, vs_point))

All occurence of ndc should be checked and renamed appropriately as well as the functions like point_world_to_ndc which does output clip space points.

References:
https://en.wikipedia.org/wiki/Clip_coordinates
https://carmencincotti.com/2022-05-02/homogeneous-coordinates-clip-space-ndc/

Throughout the GLSL codebase Clip Space and NDC Space are both refereed using the same prefix `ndc_`. But they aren't the same thing: - Clip space is what comes out of the projection matrix multiplication (i.e:`vec4 clip_point = winmat * vec4(vs_point, 1.0)` or more commonly `vec4 clip_point = point_world_to_ndc(vs_point)`) - NDC (Normalized Device Coordinate) is the result of the perspective division (i.e: `vec3 ndc_point = clip_point.xyz / clip_point.w` or more commonly `vec3 ndc_point = project_point(winmat, vs_point)`) All occurence of `ndc` should be checked and renamed appropriately as well as the functions like `point_world_to_ndc` which does output clip space points. References: https://en.wikipedia.org/wiki/Clip_coordinates https://carmencincotti.com/2022-05-02/homogeneous-coordinates-clip-space-ndc/

Clément Foucault added the

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To Do

label 2023-02-22 13:26:03 +01:00

Clément Foucault added this to the EEVEE & Viewport project 2023-02-22 13:26:03 +01:00

Clément Foucault referenced this issue

2023-02-22 13:47:50 +01:00

WIP: Use a different method for overlay edit mesh bias #104921

Prakhar-Singh-Chouhan commented

2023-02-24 15:33:58 +01:00

this issue is open right ? Could you please explain to me in more detail what needs to be done here?

Clément Foucault commented

2023-02-24 17:56:20 +01:00

@Prakhar-Singh-Chouhan Yes, this issue is still opened.

The list of things to do is:

Check all variable names that contain ndc_ and change them to hs_ (short for homogeneous space) if they are comming from a projection matrix multiplication without division.
Check all function names that contain ndc and change them to homegeneous if they are working with the homogeneous space.
Rename point_view_to_ndc to point_view_to_homogeneous.
Rename point_world_to_ndc to point_world_to_homogeneous.
Rename point_object_to_ndc to point_object_to_homogeneous.

gl_Location is expected to be in homogeneous space.

@Prakhar-Singh-Chouhan Yes, this issue is still opened. The list of things to do is: - Check all variable names that contain `ndc_` and change them to `hs_` (short for homogeneous space) if they are comming from a projection matrix multiplication without division. - Check all function names that contain `ndc` and change them to `homegeneous` if they are working with the homogeneous space. - Rename `point_view_to_ndc` to `point_view_to_homogeneous`. - Rename `point_world_to_ndc` to `point_world_to_homogeneous`. - Rename `point_object_to_ndc` to `point_object_to_homogeneous`. `gl_Location` is expected to be in homogeneous space.

Jorijn de Graaf commented

2023-02-27 03:31:25 +01:00

If you haven't started working on this yet, I wouldn't mind giving it a go.