From 53d063246b03c4fd50f31bc981b1f0c9f9a9b000 Mon Sep 17 00:00:00 2001
From: David Allemang <david.allemang@kitware.com>
Date: Mon, 8 Jul 2024 10:51:42 -0400
Subject: [PATCH] pass a uniform

---
 src/Uber.zig              |  9 ++------
 src/main.zig              | 48 ++++++++++++++++++++++++++++++++++++++-
 src/shaders/triangle.vert | 12 ++++++----
 3 files changed, 57 insertions(+), 12 deletions(-)

diff --git a/src/Uber.zig b/src/Uber.zig
index 1a64888..3144a25 100644
--- a/src/Uber.zig
+++ b/src/Uber.zig
@@ -44,14 +44,9 @@ pub const Vertex = extern struct {
 };
 
 pub const Uniform = extern struct {
-    proj: [16]f32 = .{
-        0.5, 0, 0, 0,
-        0,   1, 0, 0,
-        0,   0, 1, 0,
-        0,   0, 0, 1,
-    },
+    proj: [16]f32,
 
-    const DescriptorLayoutInfo = vk.DescriptorSetLayoutCreateInfo{
+    pub const DescriptorLayoutInfo = vk.DescriptorSetLayoutCreateInfo{
         .flags = .{},
         .binding_count = 1,
         .p_bindings = &.{
diff --git a/src/main.zig b/src/main.zig
index 203eb21..ccd4d87 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -23,7 +23,14 @@ const vertices = [_]Uber.Vertex{
 
 const indices = [_]Uber.Index{ 4, 5, 6, 6, 5, 7 };
 
-const uniform = Uber.Uniform{};
+const uniform = Uber.Uniform{
+    .proj = .{
+        0.5, 0.0, 0.0, 0.0,
+        0.0, 1.0, 0.0, 0.0,
+        0.0, 0.0, 1.0, 0.0,
+        0.0, 0.0, 0.0, 1.0,
+    },
+};
 
 const Frame = struct {
     pub fn init() !Frame {
@@ -41,9 +48,11 @@ const Frame = struct {
         view: vk.ImageView,
         scissor: vk.Rect2D,
         pipeline: vk.Pipeline,
+        layout: vk.PipelineLayout,
         vertex_buffer: vk.Buffer,
         index_buffer: vk.Buffer,
         uniform_buffer: vk.Buffer,
+        descriptor_set: vk.DescriptorSet,
     ) !void {
         _ = self;
 
@@ -103,6 +112,7 @@ const Frame = struct {
 
         cmd.beginRendering(&info);
 
+        cmd.bindDescriptorSets(.graphics, layout, 0, 1, &.{descriptor_set}, 0, null);
         cmd.bindPipeline(.graphics, pipeline);
         cmd.bindVertexBuffers(0, 1, &.{vertex_buffer}, &.{0});
         cmd.bindIndexBuffer(index_buffer, 0, .uint16);
@@ -282,6 +292,8 @@ pub fn main() !void {
     defer au.D.unmapMemory(index_memory);
     index_data.* = indices;
 
+    // todo ring buffer for frames in flight. need to use an offset when binding
+    // use dynamic offset - descriptor type VK_DESCRIPTOR_TYPE_UNIFORM_BUFFER_DYNAMIC
     const uniform_buffer = try au.D.createBuffer(&vk.BufferCreateInfo{
         .size = @sizeOf(@TypeOf(uniform)),
         .usage = .{ .uniform_buffer_bit = true },
@@ -299,6 +311,38 @@ pub fn main() !void {
     defer au.D.unmapMemory(uniform_memory);
     uniform_data.* = uniform;
 
+    var descriptorSet: vk.DescriptorSet = undefined;
+    try au.D.allocateDescriptorSets(&vk.DescriptorSetAllocateInfo{
+        .descriptor_pool = descriptorPool,
+        .descriptor_set_count = 1,
+        .p_set_layouts = &.{uber.set_layout},
+    }, @ptrCast(&descriptorSet));
+    defer au.D.freeDescriptorSets(descriptorPool, 1, &.{descriptorSet}) catch unreachable; // todo handle this?
+
+    au.D.updateDescriptorSets(
+        1,
+        &.{
+            vk.WriteDescriptorSet{
+                .dst_set = descriptorSet,
+                .dst_binding = 0,
+                .dst_array_element = 0,
+                .descriptor_type = .uniform_buffer,
+                .descriptor_count = 1,
+                .p_image_info = &[0]vk.DescriptorImageInfo{},
+                .p_texel_buffer_view = &[0]vk.BufferView{},
+                .p_buffer_info = &.{
+                    vk.DescriptorBufferInfo{
+                        .buffer = uniform_buffer,
+                        .offset = 0,
+                        .range = vk.WHOLE_SIZE,
+                    },
+                },
+            },
+        },
+        0,
+        null,
+    );
+
     var prng = std.Random.Sfc64.init(std.crypto.random.int(u64));
     const rand = prng.random();
 
@@ -350,9 +394,11 @@ pub fn main() !void {
             view,
             vk.Rect2D{ .offset = .{ .x = 0, .y = 0 }, .extent = sc.cinfo.image_extent },
             uber.pipeline,
+            uber.layout,
             vertex_buffer,
             index_buffer,
             uniform_buffer,
+            descriptorSet,
         );
 
         for (vertex_data) |*v| {
diff --git a/src/shaders/triangle.vert b/src/shaders/triangle.vert
index f820750..f98be1c 100644
--- a/src/shaders/triangle.vert
+++ b/src/shaders/triangle.vert
@@ -1,11 +1,15 @@
 #version 450
 
-layout(location = 0) in vec4 a_pos;
-layout(location = 1) in vec3 a_color;
+layout (set = 0, binding = 0) uniform CameraBuffer {
+    mat4 viewproj;
+} cam;
 
-layout(location = 0) out vec3 v_color;
+layout (location = 0) in vec4 a_pos;
+layout (location = 1) in vec3 a_color;
+
+layout (location = 0) out vec3 v_color;
 
 void main() {
-    gl_Position = a_pos;
+    gl_Position = a_pos * cam.viewproj;
     v_color = a_color;
 }