From 2722ccccdb1f91cb266a1325d1f723c2719eb9a0 Mon Sep 17 00:00:00 2001
From: Nicola Papale <nico@nicopap.ch>
Date: Wed, 22 Dec 2021 17:54:29 +0100
Subject: [PATCH] Remove indices of immediate mod line meshes

With bevyengine/bevy#3415 it is now possible to upload meshes to GPU
without `indices` set. Before, it would panic. Removing `indices`
enables us to simply remove the `ImmLinesStorage::fill_indices` code,
since the ordering is exactly as the GPU would interpret the mesh
otherwise.
---
 Cargo.toml     |  2 +-
 examples/3d.rs |  2 +-
 src/lib.rs     | 31 +++++++------------------------
 3 files changed, 9 insertions(+), 26 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index b229d82..49abc23 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,7 +16,7 @@ exclude = ["demo.gif", "demo_2.png", "demo_2.webm"]
 bevy = { version = "0.5", default-features = false, features = [ "render" ] }
 
 [patch.crates-io]
-bevy = { git = "https://github.com/bevyengine/bevy", rev = "a3c53e689d62a2fd403bf0236b5638e569bd5600" }
+bevy = { git = "https://github.com/nicopap/bevy", branch = "implement-non-indexed-drawing" }
 
 [features]
 example_deps = [
diff --git a/examples/3d.rs b/examples/3d.rs
index 77be96f..b75d748 100644
--- a/examples/3d.rs
+++ b/examples/3d.rs
@@ -23,7 +23,7 @@ fn setup(mut commands: Commands, mut lines: DebugLines) {
         Vec3::new(-1.0, 1.0, 1.0),
         100.0,
         Color::CYAN,
-        Color::ORANGE_RED,
+        Color::MIDNIGHT_BLUE,
     );
 }
 
diff --git a/src/lib.rs b/src/lib.rs
index 946804d..a8a8d60 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -73,8 +73,9 @@ pub const MAX_LINES: usize = MAX_POINTS / 2;
 pub const MAX_POINTS: usize = MAX_POINTS_PER_MESH * DEBUG_LINES_MESH_COUNT;
 
 fn spawn_debug_lines_mesh(meshes: &mut Assets<Mesh>, retain: DebugLinesMesh) -> impl Bundle {
+    let is_immediate = matches!(retain, DebugLinesMesh::Immediate(_));
     (
-        meshes.add(debug_lines_mesh()),
+        meshes.add(debug_lines_mesh(is_immediate)),
         Transform::default(),
         GlobalTransform::default(),
         Visibility::default(),
@@ -111,7 +112,7 @@ fn update_debug_lines_mesh(
 }
 
 /// Initialize [`DebugLinesMesh`]'s [`Mesh`].
-fn debug_lines_mesh() -> Mesh {
+fn debug_lines_mesh(is_immediate: bool) -> Mesh {
     let mut mesh = Mesh::new(PrimitiveTopology::LineList);
     mesh.set_attribute(
         Mesh::ATTRIBUTE_POSITION,
@@ -121,7 +122,9 @@ fn debug_lines_mesh() -> Mesh {
         Mesh::ATTRIBUTE_COLOR,
         VertexAttributeValues::Float32x4(Vec::with_capacity(256)),
     );
-    mesh.set_indices(Some(Indices::U16(Vec::with_capacity(256))));
+    if !is_immediate {
+        mesh.set_indices(Some(Indices::U16(Vec::with_capacity(256))));
+    }
     mesh
 }
 
@@ -194,23 +197,6 @@ impl ImmLinesStorage {
         }
     }
 
-    fn fill_indices(&self, buffer: &mut Vec<u16>, mesh: usize) {
-        buffer.clear();
-        let start = mesh << 16;
-        let end = (mesh + 1) << 16;
-        let buffer_size = self.positions.len();
-        let indices = if start < buffer_size && buffer_size >= end {
-            // Because MAX_POINTS_PER_MESH == 2^16
-            0xFFFF_u16
-        } else if start < buffer_size && buffer_size < end {
-            (buffer_size - start) as u16
-        } else {
-            0
-        };
-        // Because MAX_POINTS_PER_MESH == 2^16, this needs to be inclusive
-        buffer.extend(0..=indices);
-    }
-
     fn mark_expired(&mut self) {
         self.positions.clear();
         self.colors.clear();
@@ -232,9 +218,6 @@ impl ImmLinesStorage {
 
     fn fill_attributes(&self, mesh: &mut Mesh, mesh_index: usize) {
         use VertexAttributeValues::{Float32x3, Float32x4};
-        if let Some(Indices::U16(indices)) = mesh.indices_mut() {
-            self.fill_indices(indices, mesh_index);
-        }
         if let Some(Float32x3(vbuffer)) = mesh.attribute_mut(Mesh::ATTRIBUTE_POSITION) {
             self.fill_vertexes(vbuffer, mesh_index);
         }
@@ -458,7 +441,7 @@ impl SpecializedPipeline for DebugLinePipeline {
         descriptor.fragment.as_mut().unwrap().shader = self.shader.clone_weak();
         descriptor.primitive.topology = PrimitiveTopology::LineList;
         descriptor.primitive.cull_mode = None;
-        // TODO: set this to None to remove depth check
+        // TODO: set this to a large value to remove depth check
         descriptor.depth_stencil.as_mut().unwrap().bias.slope_scale = 1.0;
         descriptor
     }