Mirrors/bevy
2
0
Fork 0
mirror of https://github.com/bevyengine/bevy synced 2024-11-10 07:04:33 +00:00
Code Issues Projects Releases Packages Wiki Activity

Fix gizmo lines deforming or disappearing when partially behind the camera (#9470)

Browse source 
If a line has one point behind the camera(near plane) then it would
deform or, if the `depth_bias` setting was set to a negative value,
disappear.

## Solution

The issue is that performing a perspective divide does not work
correctly for points behind the near plane and a perspective divide is
used inside the shader to define the line width in screen space.
The solution is to perform near plane clipping manually inside the
shader before the perspective divide is done.
This commit is contained in:
ira 2023-08-17 22:09:19 +02:00 committed by Carter Anderson
parent 94e81c2855
commit 5b0798f029
1 changed files with 19 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

21
crates/bevy_gizmos/src/lines.wgsl
View file

@ -43,8 +43,13 @@ fn vertex(vertex: VertexInput) -> VertexOutput {
let position = positions[vertex.index];
// algorithm based on https://wwwtyro.net/2019/11/18/instanced-lines.html
let clip_a = view.view_proj * vec4(vertex.position_a, 1.);
let clip_b = view.view_proj * vec4(vertex.position_b, 1.);
var clip_a = view.view_proj * vec4(vertex.position_a, 1.);
var clip_b = view.view_proj * vec4(vertex.position_b, 1.);
// Manual near plane clipping to avoid errors when doing the perspective divide inside this shader.
clip_a = clip_near_plane(clip_a, clip_b);
clip_b = clip_near_plane(clip_b, clip_a);
let clip = mix(clip_a, clip_b, position.z);
let resolution = view.viewport.zw;
@ -92,6 +97,18 @@ fn vertex(vertex: VertexInput) -> VertexOutput {
return VertexOutput(clip_position, color);
}
fn clip_near_plane(a: vec4<f32>, b: vec4<f32>) -> vec4<f32> {
// Move a if a is behind the near plane and b is in front.
if a.z > a.w && b.z <= b.w {
// Interpolate a towards b until it's at the near plane.
let distance_a = a.z - a.w;
let distance_b = b.z - b.w;
let t = distance_a / (distance_a - distance_b);
return a + (b - a) * t;
}
return a;
}
struct FragmentInput {
@location(0) color: vec4<f32>,
};