adding draw indexed

src/soft/device/vertex_dispatcher.zig

@@ -18,6 +18,9 @@ pub const RunData = struct {
     batch_id: usize,
     batch_size: usize,
     vertex_count: usize,
+    first_vertex: usize,
+    first_instance: usize,
+    indices: ?[]const u32,
     instance_index: usize,
     draw_call: *Renderer.DrawCall,
 };
@@ -41,7 +44,10 @@ inline fn run(data: RunData) !void {
 
     var invocation_index: usize = data.batch_id;
     while (invocation_index < data.vertex_count) : (invocation_index += data.batch_size) {
-        setupBuiltins(rt, invocation_index, data.instance_index) catch |err| switch (err) {
+        const vertex_index = if (data.indices) |indices| indices[invocation_index] else data.first_vertex + invocation_index;
+        const instance_index = data.first_instance + data.instance_index;
+
+        setupBuiltins(rt, vertex_index, instance_index) catch |err| switch (err) {
             SpvRuntimeError.NotFound => {},
             else => return err,
         };
@@ -56,7 +62,7 @@ inline fn run(data: RunData) !void {
                 const buffer = vertex_buffer.buffer;
                 const buffer_memory_size = base.format.texelSize(attribute.format);
                 const buffer_memory = if (buffer.interface.memory) |memory| memory else return VkError.InvalidDeviceMemoryDrv;
-                const offset = buffer.interface.offset + (binding_info.stride * invocation_index) + attribute.offset;
+                const offset = buffer.interface.offset + vertex_buffer.offset + (binding_info.stride * vertex_index) + attribute.offset;
 
                 const buffer_memory_map: []u8 = @as([*]u8, @ptrCast(@alignCast(try buffer_memory.map(offset, buffer_memory_size))))[0..buffer_memory_size];
 
@@ -89,7 +95,7 @@ inline fn run(data: RunData) !void {
     }
 }
 
-fn setupBuiltins(rt: *spv.Runtime, invocation_index: usize, instance_index: usize) !void {
-    try rt.writeBuiltIn(std.mem.asBytes(&invocation_index), .VertexIndex);
+fn setupBuiltins(rt: *spv.Runtime, vertex_index: usize, instance_index: usize) !void {
+    try rt.writeBuiltIn(std.mem.asBytes(&vertex_index), .VertexIndex);
     try rt.writeBuiltIn(std.mem.asBytes(&instance_index), .InstanceIndex);
 }