From a4afa4e7f3e572803bded6409fa5871e1a39fe03 Mon Sep 17 00:00:00 2001
From: Carter Anderson <mcanders1@gmail.com>
Date: Fri, 26 Jun 2020 14:27:22 -0700
Subject: [PATCH] render: only attempt to create camera bind group when the
 camera bind group descriptor exists

this fixes panics in empty scenes
---
 .../src/render_graph/nodes/pass_node.rs            | 14 +++++++++-----
 .../renderer/headless_render_resource_context.rs   |  4 ++++
 .../src/renderer/render_resource_context.rs        |  2 ++
 .../src/renderer/wgpu_render_resource_context.rs   |  8 ++++++++
 4 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/crates/bevy_render/src/render_graph/nodes/pass_node.rs b/crates/bevy_render/src/render_graph/nodes/pass_node.rs
index 763a38249a..42d2c89684 100644
--- a/crates/bevy_render/src/render_graph/nodes/pass_node.rs
+++ b/crates/bevy_render/src/render_graph/nodes/pass_node.rs
@@ -135,12 +135,16 @@ impl Node for PassNode {
                 } else {
                     continue;
                 };
-
-            let camera_bind_group = BindGroup::build().add_binding(0, camera_binding).finish();
-            render_context
+            if render_context
                 .resources()
-                .create_bind_group(self.camera_bind_group_descriptor.id, &camera_bind_group);
-            camera_info.bind_group_id = Some(camera_bind_group.id);
+                .bind_group_descriptor_exists(self.camera_bind_group_descriptor.id)
+            {
+                let camera_bind_group = BindGroup::build().add_binding(0, camera_binding).finish();
+                render_context
+                    .resources()
+                    .create_bind_group(self.camera_bind_group_descriptor.id, &camera_bind_group);
+                camera_info.bind_group_id = Some(camera_bind_group.id);
+            }
         }
 
         render_context.begin_pass(
diff --git a/crates/bevy_render/src/renderer/headless_render_resource_context.rs b/crates/bevy_render/src/renderer/headless_render_resource_context.rs
index 6f7e566a32..8e72dbe27f 100644
--- a/crates/bevy_render/src/renderer/headless_render_resource_context.rs
+++ b/crates/bevy_render/src/renderer/headless_render_resource_context.rs
@@ -120,4 +120,8 @@ impl RenderResourceContext for HeadlessRenderResourceContext {
     fn get_buffer_info(&self, buffer: BufferId) -> Option<BufferInfo> {
         self.buffer_info.read().unwrap().get(&buffer).cloned()
     }
+    fn bind_group_descriptor_exists(&self, _bind_group_descriptor_id: BindGroupDescriptorId)
+        -> bool {
+        false
+    }
 }
diff --git a/crates/bevy_render/src/renderer/render_resource_context.rs b/crates/bevy_render/src/renderer/render_resource_context.rs
index 4edc6730be..d4521e3124 100644
--- a/crates/bevy_render/src/renderer/render_resource_context.rs
+++ b/crates/bevy_render/src/renderer/render_resource_context.rs
@@ -48,6 +48,8 @@ pub trait RenderResourceContext: Downcast + Send + Sync + 'static {
         pipeline_descriptor: &PipelineDescriptor,
         shaders: &Assets<Shader>,
     );
+    fn bind_group_descriptor_exists(&self, bind_group_descriptor_id: BindGroupDescriptorId)
+        -> bool;
     fn create_bind_group(
         &self,
         bind_group_descriptor_id: BindGroupDescriptorId,
diff --git a/crates/bevy_wgpu/src/renderer/wgpu_render_resource_context.rs b/crates/bevy_wgpu/src/renderer/wgpu_render_resource_context.rs
index a7bbe18aac..77045ff1ef 100644
--- a/crates/bevy_wgpu/src/renderer/wgpu_render_resource_context.rs
+++ b/crates/bevy_wgpu/src/renderer/wgpu_render_resource_context.rs
@@ -433,6 +433,14 @@ impl RenderResourceContext for WgpuRenderResourceContext {
         render_pipelines.insert(pipeline_handle, render_pipeline);
     }
 
+    fn bind_group_descriptor_exists(
+        &self,
+        bind_group_descriptor_id: BindGroupDescriptorId,
+    ) -> bool {
+        let bind_group_layouts = self.resources.bind_group_layouts.read().unwrap();
+        bind_group_layouts.get(&bind_group_descriptor_id).is_some()
+    }
+
     fn create_bind_group(
         &self,
         bind_group_descriptor_id: BindGroupDescriptorId,