Add depth to 3D contours and isosurfaces

GLMakie/assets/shader/volume.frag

@@ -25,6 +25,8 @@ uniform int algorithm;
 uniform float isovalue;
 uniform float isorange;
 
+uniform mat4 model, projectionview;
+
 const float max_distance = 1.3;
 
 const int num_samples = 200;
@@ -206,11 +208,17 @@ vec4 contours(vec3 front, vec3 dir)
     vec3 Lo = vec3(0.0);
     int i = 0;
     vec3 camdir = normalize(-dir);
+    {{depth_init}}
+    // may write: float depth = 100000.0;
     for (i; i < num_samples; ++i) {
         float intensity = texture(volumedata, pos).x;
         vec4 density = color_lookup(intensity, color_map, color_norm, color);
         float opacity = density.a;
         if(opacity > 0.0){
+            {{depth_main}}
+            // may write
+            // vec4 frag_coord = projectionview * model * vec4(pos, 1);
+            // depth = min(depth, frag_coord.z / frag_coord.w);
             vec3 N = gennormal(pos, step_size);
             vec3 L = normalize(o_light_dir - pos);
             vec3 opaque = blinnphong(N, camdir, L, density.rgb);
@@ -221,6 +229,9 @@ vec4 contours(vec3 front, vec3 dir)
         }
         pos += dir;
     }
+    {{depth_write}}
+    // may write:
+    // gl_FragDepth = depth == 100000.0 ? gl_FragDepth : 0.5 * depth + 0.5;
     return vec4(Lo, 1-T);
 }
 
@@ -231,9 +242,15 @@ vec4 isosurface(vec3 front, vec3 dir)
     int i = 0;
     vec4 diffuse_color = color_lookup(isovalue, color_map, color_norm, color);
     vec3 camdir = normalize(-dir);
+    {{depth_init}}
+    // may write: float depth = 100000.0;
     for (i; i < num_samples; ++i){
         float density = texture(volumedata, pos).x;
         if(abs(density - isovalue) < isorange){
+            {{depth_main}}
+            // may write:
+            // vec4 frag_coord = projectionview * model * vec4(pos, 1);
+            // depth = min(depth, frag_coord.z / frag_coord.w);
             vec3 N = gennormal(pos, step_size);
             vec3 L = normalize(o_light_dir - pos);
             // back & frontface...
@@ -244,6 +261,9 @@ vec4 isosurface(vec3 front, vec3 dir)
         }
         pos += dir;
     }
+    {{depth_write}}
+    // may write:
+    // gl_FragDepth = depth == 100000.0 ? gl_FragDepth : 0.5 * depth + 0.5;
     return c;
 }
 

GLMakie/src/GLVisualize/visualize/image_like.jl

@@ -94,13 +94,36 @@ function _default(main::VolumeTypes{T}, s::Style, data::Dict) where T <: VolumeE
         absorption = 1f0
         isovalue = 0.5f0
         isorange = 0.01f0
-        shader = GLVisualizeShader("fragment_output.frag", "util.vert", "volume.vert", "volume.frag")
+        enable_depth = true
+        shader = GLVisualizeShader(
+            "fragment_output.frag", "util.vert", "volume.vert", "volume.frag",
+            view = Dict(
+                "depth_init"  => vol_depth_init(to_value(enable_depth)),
+                "depth_main"  => vol_depth_main(to_value(enable_depth)),
+                "depth_write" => vol_depth_write(to_value(enable_depth))
+            )
+        )
         prerender = VolumePrerender(data[:transparency], data[:overdraw])
         postrender = () -> glDisable(GL_CULL_FACE)
     end
     return data
 end
 
+vol_depth_init(enable) = enable ? "float depth = 100000.0;" : ""
+function vol_depth_main(enable)
+    if enable
+        """
+        vec4 frag_coord = projectionview * model * vec4(pos, 1);
+        depth = min(depth, frag_coord.z / frag_coord.w);
+        """
+    else "" end
+end
+function vol_depth_write(enable)
+    if enable
+        "gl_FragDepth = depth == 100000.0 ? gl_FragDepth : 0.5 * depth + 0.5;"
+    else "" end
+end
+
 function _default(main::VolumeTypes{T}, s::Style, data::Dict) where T <: RGBA
     @gen_defaults! data begin
         volumedata = main => Texture

GLMakie/test/glmakie_tests.jl

@@ -90,3 +90,17 @@ end
     set_window_config!(renderloop=GLMakie.renderloop)
     fig
 end
+
+@cell "Contour and isosurface with correct depth" begin
+    # Make sure shaders can recompile
+    close(GLMakie.global_gl_screen())
+
+    fig = Figure()
+    left = LScene(fig[1, 1])
+    contour!(left, [sin(i+j) * sin(j+k) * sin(i+k) for i in 1:10, j in 1:10, k in 1:10], enable_depth = true)
+    mesh!(left, Sphere(Point3f(5), 6f0))
+    right = LScene(fig[1, 2])
+    volume!(right, [sin(2i) * sin(2j) * sin(2k) for i in 1:10, j in 1:10, k in 1:10], algorithm = :iso, enable_depth = true)
+    mesh!(right, Sphere(Point3f(5), 6f0))
+    fig
+end

src/basic_recipes/contours.jl

@@ -26,7 +26,8 @@ $(ATTRIBUTES)
         levels = 5,
         linewidth = 1.0,
         alpha = 1.0,
-        fillrange = false
+        fillrange = false,
+        enable_depth = true
     )
 end
 
@@ -114,7 +115,8 @@ function plot!(plot::Contour{<: Tuple{X, Y, Z, Vol}}) where {X, Y, Z, Vol}
         plot, x, y, z, volume, colormap = cmap, colorrange = cliprange, algorithm = 7,
         transparency = plot.transparency, overdraw = plot.overdraw,
         ambient = plot.ambient, diffuse = plot.diffuse, lightposition = plot.lightposition,
-        shininess = plot.shininess, specular = plot.specular, inspectable = plot.inspectable
+        shininess = plot.shininess, specular = plot.specular, inspectable = plot.inspectable,
+        enable_depth = plot.enable_depth
     )
 end