Use (2, 0) for instance data (#18)

Author: karnkaul

assets/shader.vert

@@ -41,13 +41,19 @@ vk::DescriptorPoolSize{vk::DescriptorType::eCombinedImageSampler, 2},
 vk::DescriptorPoolSize{vk::DescriptorType::eStorageBuffer, 2},
 ```
 
-This time add a new binding to set 1 (instead of a new set):
+Add set 2 and its new binding. Such a set layout keeps each "layer" isolated:
+
+* Set 0: view / camera
+* Set 1: textures / material
+* Set 2: draw instances
 
 ```cpp
-static constexpr auto set_1_bindings_v = std::array{
-  layout_binding(0, vk::DescriptorType::eCombinedImageSampler),
+static constexpr auto set_2_bindings_v = std::array{
   layout_binding(1, vk::DescriptorType::eStorageBuffer),
 };
+auto set_layout_cis = std::array<vk::DescriptorSetLayoutCreateInfo, 3>{};
+// ...
+set_layout_cis[2].setBindings(set_2_bindings_v);
 ```
 
 Create the instance SSBO after the view UBO:
@@ -98,13 +104,14 @@ Add another descriptor write for the SSBO:
 ```cpp
 auto writes = std::array<vk::WriteDescriptorSet, 3>{};
 // ...
+auto const set2 = descriptor_sets[2];
 auto const instance_ssbo_info =
   m_instance_ssbo->descriptor_info_at(m_frame_index);
 write.setBufferInfo(instance_ssbo_info)
   .setDescriptorType(vk::DescriptorType::eStorageBuffer)
   .setDescriptorCount(1)
-  .setDstSet(set1)
-  .setDstBinding(1);
+  .setDstSet(set2)
+  .setDstBinding(0);
 writes[2] = write;
 ```
 

guide/src/descriptor_sets/instanced_rendering.md

@@ -272,11 +272,14 @@ void App::create_pipeline_layout() {
 	};
 	static constexpr auto set_1_bindings_v = std::array{
 		layout_binding(0, vk::DescriptorType::eCombinedImageSampler),
-		layout_binding(1, vk::DescriptorType::eStorageBuffer),
 	};
-	auto set_layout_cis = std::array<vk::DescriptorSetLayoutCreateInfo, 2>{};
+	static constexpr auto set_2_bindings_v = std::array{
+		layout_binding(0, vk::DescriptorType::eStorageBuffer),
+	};
+	auto set_layout_cis = std::array<vk::DescriptorSetLayoutCreateInfo, 3>{};
 	set_layout_cis[0].setBindings(set_0_bindings_v);
 	set_layout_cis[1].setBindings(set_1_bindings_v);
+	set_layout_cis[2].setBindings(set_2_bindings_v);
 
 	for (auto const& set_layout_ci : set_layout_cis) {
 		m_set_layouts.push_back(
@@ -656,13 +659,15 @@ void App::bind_descriptor_sets(vk::CommandBuffer const command_buffer) const {
 		.setDstSet(set1)
 		.setDstBinding(0);
 	writes[1] = write;
+
+	auto const set2 = descriptor_sets[2];
 	auto const instance_ssbo_info =
 		m_instance_ssbo->descriptor_info_at(m_frame_index);
 	write.setBufferInfo(instance_ssbo_info)
 		.setDescriptorType(vk::DescriptorType::eStorageBuffer)
 		.setDescriptorCount(1)
-		.setDstSet(set1)
-		.setDstBinding(1);
+		.setDstSet(set2)
+		.setDstBinding(0);
 	writes[2] = write;
 
 	m_device->updateDescriptorSets(writes, {});

src/app.cpp

@@ -8,7 +8,7 @@ layout (set = 0, binding = 0) uniform View {
 	mat4 mat_vp;
 };
 
-layout (set = 1, binding = 1) readonly buffer Instances {
+layout (set = 2, binding = 0) readonly buffer Instances {
 	mat4 mat_ms[];
 };