Cleanup voxel clipping

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - Show DataInspector tooltip on NaN values if `nan_color` has been set to other than `:transparent` [#4310](https://github.com/MakieOrg/Makie.jl/pull/4310)
 - Fix `linestyle` not being used in `triplot` [#4332](https://github.com/MakieOrg/Makie.jl/pull/4332)
+- Fix voxel clipping not being based on voxel centers [#4397](https://github.com/MakieOrg/Makie.jl/pull/4397)
 
 ## [0.21.11] - 2024-09-13
 

CairoMakie/src/primitives.jl

@@ -1253,7 +1253,14 @@ function draw_atomic(scene::Scene, screen::Screen, @nospecialize(primitive::Maki
     pos = Makie.voxel_positions(primitive)
     scale = Makie.voxel_size(primitive)
     colors = Makie.voxel_colors(primitive)
-    marker = normal_mesh(Rect3f(Point3f(-0.5), Vec3f(1)))
+    marker = GeometryBasics.normal_mesh(Rect3f(Point3f(-0.5), Vec3f(1)))
+
+    # Face culling
+    if !isempty(primitive.clip_planes[]) && Makie.is_data_space(primitive.space[])
+        valid = [is_visible(primitive.clip_planes[], p) for p in pos]
+        pos = pos[valid]
+        colors = colors[valid]
+    end
 
     # For correct z-ordering we need to be in view/camera or screen space
     model = copy(primitive.model[])
@@ -1271,7 +1278,7 @@ function draw_atomic(scene::Scene, screen::Screen, @nospecialize(primitive::Maki
         specular = primitive.specular, shininess = primitive.shininess,
         faceculling = get(primitive, :faceculling, -10),
         transformation = Makie.transformation(primitive),
-        clip_planes = primitive.clip_planes
+        clip_planes = Plane3f[]
     )
 
     for i in zorder

GLMakie/assets/shader/voxel.frag

@@ -85,18 +85,16 @@ vec4 get_color(sampler2D color, Nothing color_map, int id) {
 
 bool is_clipped()
 {
-    float d1, d2;
+    float d;
+    // Center of voxel
     ivec3 size = ivec3(textureSize(voxel_id, 0).xyz);
-    vec3 xyz = vec3(ivec3(o_uvw * size));
+    vec3 xyz = vec3(ivec3(o_uvw * size)) + vec3(0.5);
     for (int i = 0; i < _num_clip_planes; i++) {
-        // distance from clip planes with negative clipped
-        d1 = dot(xyz, clip_planes[i].xyz) - clip_planes[i].w;
-        d2 = dot(xyz, clip_planes[i].xyz) - clip_planes[i].w;
+        // distance between clip plane and center
+        d = dot(xyz, clip_planes[i].xyz) - clip_planes[i].w;
 
-        // both outside - clip everything
-        if (d1 < 0.0 || d2 < 0.0) {
+        if (d < 0.0) 
             return true;
-        }
     }
 
     return false;

ReferenceTests/src/tests/examples3d.jl

@@ -682,7 +682,7 @@ end
 @reference_test "Clip planes - voxel" begin
     f = Figure()
     a = LScene(f[1, 1])
-    a.scene.theme[:clip_planes][] = [Plane3f(Vec3f(-2, -1, -0.5), 0.0), Plane3f(Vec3f(-0.5, -1, -2), 0.0)]
+    a.scene.theme[:clip_planes][] = [Plane3f(Vec3f(-2, -1, -0.5), 0.1), Plane3f(Vec3f(-0.5, -1, -2), 0.1)]
     r = -10:10
     p = voxels!(a, [cos(sin(x+y)+z) for x in r, y in r, z in r])
     f

WGLMakie/assets/voxel.frag

@@ -85,18 +85,15 @@ vec3 blinnphong(vec3 N, vec3 V, vec3 L, vec3 color){
 
 bool is_clipped()
 {
-    float d1, d2;
+    float d;
+    // get center pos of this voxel
     vec3 size = vec3(textureSize(voxel_id, 0).xyz);
-    vec3 xyz = vec3(ivec3(o_uvw * size));
+    vec3 xyz = vec3(ivec3(o_uvw * size)) + vec3(0.5);
     for (int i = 0; i < num_clip_planes; i++) {
-        // distance from clip planes with negative clipped
-        d1 = dot(xyz, clip_planes[i].xyz) - clip_planes[i].w;
-        d2 = dot(xyz, clip_planes[i].xyz) - clip_planes[i].w;
-
-        // both outside - clip everything
-        if (d1 < 0.0 || d2 < 0.0) {
+        // distance between clip plane and voxel center
+        d = dot(xyz, clip_planes[i].xyz) - clip_planes[i].w;
+        if (d < 0.0)
             return true;
-        }
     }
 
     return false;