volumetric changing unlighted sphere

assets/shaders/material.wgsl

@@ -1,30 +1,46 @@
 #import bevy_pbr::{
     forward_io::{VertexOutput, FragmentOutput},
-    pbr_fragment::pbr_input_from_standard_material,
-    pbr_functions::{alpha_discard, apply_pbr_lighting, main_pass_post_lighting_processing},
+    mesh_view_bindings::view,
 }
 
-struct MyExtendedMaterial {
-    quantize_steps: u32,
+struct VoluMaterial {
+    mesh_translation: vec3<f32>,
+    sphere_radius: f32,
+    color: vec4<f32>,
 }
 
 @group(2) @binding(100)
-var<uniform> my_extended_material: MyExtendedMaterial;
+var<storage, read> volu_material: VoluMaterial;
+
+fn raymarch_hit(position_: vec3<f32>, direction: vec3<f32>) -> bool {
+    var position = position_;
+    for (var i = 0; i < 200; i++) {
+        if sphere_hit(position) {
+          return true;
+        }
+        position += direction * 0.01;
+    }
+    return false;
+}
+
+fn sphere_hit(p: vec3<f32>) -> bool {
+    return distance(p, volu_material.mesh_translation) < volu_material.sphere_radius;
+}
 
 @fragment
 fn fragment(
     in: VertexOutput,
     @builtin(front_facing) is_front: bool,
 ) -> FragmentOutput {
-    var pbr_input = pbr_input_from_standard_material(in, is_front);
-
-    pbr_input.material.base_color = alpha_discard(pbr_input.material, pbr_input.material.base_color);
+    let view_direction = normalize(in.world_position.xyz - view.world_position);
 
     var out: FragmentOutput;
-
-    out.color = apply_pbr_lighting(pbr_input);
-
-    out.color = main_pass_post_lighting_processing(pbr_input, out.color);
+    if (raymarch_hit(in.world_position.xyz, view_direction)) {
+      out.color = volu_material.color;
+    } else {
+      out.color = vec4(1.0, 1.0, 1.0, 0.2);
+    }
 
     return out;
 }
+