[Impeller] Make index buffer optional

impeller/core/formats.h

@@ -308,6 +308,8 @@ enum class IndexType {
   kUnknown,
   k16bit,
   k32bit,
+  /// Does not use the index buffer.
+  kNone,
 };
 
 enum class PrimitiveType {

impeller/core/vertex_buffer.h

@@ -12,11 +12,14 @@ namespace impeller {
 struct VertexBuffer {
   BufferView vertex_buffer;
   BufferView index_buffer;
-  size_t index_count = 0u;
+  // The total count of vertices, either in the vertex_buffer if the
+  // index_type is IndexType::kNone or in the index_buffer otherwise.
+  size_t vertex_count = 0u;
   IndexType index_type = IndexType::kUnknown;
 
   constexpr operator bool() const {
-    return static_cast<bool>(vertex_buffer) && static_cast<bool>(index_buffer);
+    return static_cast<bool>(vertex_buffer) &&
+           (index_type == IndexType::kNone || static_cast<bool>(index_buffer));
   }
 };
 

impeller/display_list/dl_vertices_geometry.cc

@@ -175,7 +175,7 @@ GeometryResult DlVerticesGeometry::GetPositionBuffer(
               .index_buffer = {.buffer = buffer,
                                .range =
                                    Range{total_vtx_bytes, total_idx_bytes}},
-              .index_count = index_count,
+              .vertex_count = index_count,
               .index_type = IndexType::k16bit,
           },
       .transform = Matrix::MakeOrthographic(pass.GetRenderTargetSize()) *
@@ -244,7 +244,7 @@ GeometryResult DlVerticesGeometry::GetPositionColorBuffer(
               .index_buffer = {.buffer = buffer,
                                .range =
                                    Range{total_vtx_bytes, total_idx_bytes}},
-              .index_count = index_count,
+              .vertex_count = index_count,
               .index_type = IndexType::k16bit,
           },
       .transform = Matrix::MakeOrthographic(pass.GetRenderTargetSize()) *
@@ -321,7 +321,7 @@ GeometryResult DlVerticesGeometry::GetPositionUVBuffer(
               .index_buffer = {.buffer = buffer,
                                .range =
                                    Range{total_vtx_bytes, total_idx_bytes}},
-              .index_count = index_count,
+              .vertex_count = index_count,
               .index_type = IndexType::k16bit,
           },
       .transform = Matrix::MakeOrthographic(pass.GetRenderTargetSize()) *

impeller/entity/geometry.cc

@@ -91,7 +91,6 @@ static GeometryResult ComputeUVGeometryForRect(Rect source_rect,
                                                const ContentContext& renderer,
                                                const Entity& entity,
                                                RenderPass& pass) {
-  constexpr uint16_t kRectIndicies[4] = {0, 1, 2, 3};
   auto& host_buffer = pass.GetTransientsBuffer();
 
   std::vector<Point> data(8);
@@ -108,10 +107,8 @@ static GeometryResult ComputeUVGeometryForRect(Rect source_rect,
           {
               .vertex_buffer = host_buffer.Emplace(
                   data.data(), 16 * sizeof(float), alignof(float)),
-              .index_buffer = host_buffer.Emplace(
-                  kRectIndicies, 4 * sizeof(uint16_t), alignof(uint16_t)),
-              .index_count = 4,
-              .index_type = IndexType::k16bit,
+              .vertex_count = 4,
+              .index_type = IndexType::kNone,
           },
       .transform = Matrix::MakeOrthographic(pass.GetRenderTargetSize()) *
                    entity.GetTransformation(),
@@ -141,7 +138,7 @@ GeometryResult FillPathGeometry::GetPositionBuffer(
         points.data(), points.size() * sizeof(Point), alignof(Point));
     vertex_buffer.index_buffer = host_buffer.Emplace(
         indices.data(), indices.size() * sizeof(uint16_t), alignof(uint16_t));
-    vertex_buffer.index_count = indices.size();
+    vertex_buffer.vertex_count = indices.size();
     vertex_buffer.index_type = IndexType::k16bit;
 
     return GeometryResult{
@@ -163,7 +160,7 @@ GeometryResult FillPathGeometry::GetPositionBuffer(
             vertices, vertices_count * sizeof(float), alignof(float));
         vertex_buffer.index_buffer = host_buffer.Emplace(
             indices, indices_count * sizeof(uint16_t), alignof(uint16_t));
-        vertex_buffer.index_count = indices_count;
+        vertex_buffer.vertex_count = indices_count;
         vertex_buffer.index_type = IndexType::k16bit;
         return true;
       });
@@ -729,7 +726,7 @@ GeometryResult CoverGeometry::GetPositionBuffer(const ContentContext& renderer,
                   rect.GetPoints().data(), 8 * sizeof(float), alignof(float)),
               .index_buffer = host_buffer.Emplace(
                   kRectIndicies, 4 * sizeof(uint16_t), alignof(uint16_t)),
-              .index_count = 4,
+              .vertex_count = 4,
               .index_type = IndexType::k16bit,
           },
       .transform = Matrix::MakeOrthographic(pass.GetRenderTargetSize()),
@@ -766,18 +763,15 @@ RectGeometry::~RectGeometry() = default;
 GeometryResult RectGeometry::GetPositionBuffer(const ContentContext& renderer,
                                                const Entity& entity,
                                                RenderPass& pass) {
-  constexpr uint16_t kRectIndicies[4] = {0, 1, 2, 3};
   auto& host_buffer = pass.GetTransientsBuffer();
   return GeometryResult{
       .type = PrimitiveType::kTriangleStrip,
       .vertex_buffer =
           {
               .vertex_buffer = host_buffer.Emplace(
                   rect_.GetPoints().data(), 8 * sizeof(float), alignof(float)),
-              .index_buffer = host_buffer.Emplace(
-                  kRectIndicies, 4 * sizeof(uint16_t), alignof(uint16_t)),
-              .index_count = 4,
-              .index_type = IndexType::k16bit,
+              .vertex_count = 4,
+              .index_type = IndexType::kNone,
           },
       .transform = Matrix::MakeOrthographic(pass.GetRenderTargetSize()) *
                    entity.GetTransformation(),

impeller/playground/imgui/imgui_impl_impeller.cc

@@ -256,7 +256,7 @@ void ImGui_ImplImpeller_RenderDrawData(ImDrawData* draw_data,
             .range = impeller::Range(
                 index_buffer_offset + pcmd->IdxOffset * sizeof(ImDrawIdx),
                 pcmd->ElemCount * sizeof(ImDrawIdx))};
-        vertex_buffer.index_count = pcmd->ElemCount;
+        vertex_buffer.vertex_count = pcmd->ElemCount;
         vertex_buffer.index_type = impeller::IndexType::k16bit;
         cmd.BindVertices(vertex_buffer);
         cmd.base_vertex = pcmd->VtxOffset;

impeller/renderer/backend/gles/formats_gles.h

@@ -33,6 +33,7 @@ constexpr GLenum ToMode(PrimitiveType primitive_type) {
 constexpr GLenum ToIndexType(IndexType type) {
   switch (type) {
     case IndexType::kUnknown:
+    case IndexType::kNone:
       FML_UNREACHABLE();
     case IndexType::k16bit:
       return GL_UNSIGNED_SHORT;

impeller/renderer/backend/gles/proc_table_gles.h

@@ -116,6 +116,7 @@ struct GLProc {
   PROC(DetachShader);                        \
   PROC(Disable);                             \
   PROC(DisableVertexAttribArray);            \
+  PROC(DrawArrays);                          \
   PROC(DrawElements);                        \
   PROC(Enable);                              \
   PROC(EnableVertexAttribArray);             \

impeller/renderer/backend/gles/render_pass_gles.cc

@@ -356,18 +356,15 @@ struct RenderPassData {
     /// Bind vertex and index buffers.
     ///
     auto vertex_buffer_view = command.GetVertexBuffer();
-    auto index_buffer_view = command.index_buffer;
 
-    if (!vertex_buffer_view || !index_buffer_view) {
+    if (!vertex_buffer_view) {
       return false;
     }
 
     auto vertex_buffer =
         vertex_buffer_view.buffer->GetDeviceBuffer(*transients_allocator);
-    auto index_buffer =
-        index_buffer_view.buffer->GetDeviceBuffer(*transients_allocator);
 
-    if (!vertex_buffer || !index_buffer) {
+    if (!vertex_buffer) {
       return false;
     }
 
@@ -376,11 +373,6 @@ struct RenderPassData {
             DeviceBufferGLES::BindingType::kArrayBuffer)) {
       return false;
     }
-    const auto& index_buffer_gles = DeviceBufferGLES::Cast(*index_buffer);
-    if (!index_buffer_gles.BindAndUploadDataIfNecessary(
-            DeviceBufferGLES::BindingType::kElementArrayBuffer)) {
-      return false;
-    }
 
     //--------------------------------------------------------------------------
     /// Bind the pipeline program.
@@ -423,12 +415,25 @@ struct RenderPassData {
     //--------------------------------------------------------------------------
     /// Finally! Invoke the draw call.
     ///
-    gl.DrawElements(mode,                             // mode
-                    command.index_count,              // count
-                    ToIndexType(command.index_type),  // type
-                    reinterpret_cast<const GLvoid*>(static_cast<GLsizei>(
-                        index_buffer_view.range.offset))  // indices
-    );
+    if (command.index_type == IndexType::kNone) {
+      gl.DrawArrays(mode, command.base_vertex, command.vertex_count);
+    } else {
+      // Bind the index buffer if necessary.
+      auto index_buffer_view = command.index_buffer;
+      auto index_buffer =
+          index_buffer_view.buffer->GetDeviceBuffer(*transients_allocator);
+      const auto& index_buffer_gles = DeviceBufferGLES::Cast(*index_buffer);
+      if (!index_buffer_gles.BindAndUploadDataIfNecessary(
+              DeviceBufferGLES::BindingType::kElementArrayBuffer)) {
+        return false;
+      }
+      gl.DrawElements(mode,                             // mode
+                      command.vertex_count,             // count
+                      ToIndexType(command.index_type),  // type
+                      reinterpret_cast<const GLvoid*>(static_cast<GLsizei>(
+                          index_buffer_view.range.offset))  // indices
+      );
+    }
 
     //--------------------------------------------------------------------------
     /// Unbind vertex attribs.

impeller/renderer/backend/metal/render_pass_mtl.mm

@@ -436,7 +436,7 @@ static bool Bind(PassBindingsCache& pass,
 
   fml::closure pop_debug_marker = [encoder]() { [encoder popDebugGroup]; };
   for (const auto& command : commands_) {
-    if (command.index_count == 0u) {
+    if (command.vertex_count == 0u) {
       continue;
     }
     if (command.instance_count == 0u) {
@@ -486,6 +486,28 @@ static bool Bind(PassBindingsCache& pass,
                               ShaderStage::kFragment)) {
       return false;
     }
+
+    const PrimitiveType primitive_type = pipeline_desc.GetPrimitiveType();
+    if (command.index_type == IndexType::kNone) {
+      if (command.instance_count != 1u) {
+#if TARGET_OS_SIMULATOR
+        VALIDATION_LOG << "iOS Simulator does not support instanced rendering.";
+        return false;
+#endif
+        [encoder drawPrimitives:ToMTLPrimitiveType(primitive_type)
+                    vertexStart:command.base_vertex
+                    vertexCount:command.vertex_count
+                  instanceCount:command.instance_count
+                   baseInstance:0u];
+
+      } else {
+        [encoder drawPrimitives:ToMTLPrimitiveType(primitive_type)
+                    vertexStart:command.base_vertex
+                    vertexCount:command.vertex_count];
+      }
+      continue;
+    }
+
     if (command.index_type == IndexType::kUnknown) {
       return false;
     }
@@ -503,9 +525,7 @@ static bool Bind(PassBindingsCache& pass,
       return false;
     }
 
-    const PrimitiveType primitive_type = pipeline_desc.GetPrimitiveType();
-
-    FML_DCHECK(command.index_count *
+    FML_DCHECK(command.vertex_count *
                    (command.index_type == IndexType::k16bit ? 2 : 4) ==
                command.index_buffer.range.length);
 
@@ -515,7 +535,7 @@ static bool Bind(PassBindingsCache& pass,
       return false;
 #endif
       [encoder drawIndexedPrimitives:ToMTLPrimitiveType(primitive_type)
-                          indexCount:command.index_count
+                          indexCount:command.vertex_count
                            indexType:ToMTLIndexType(command.index_type)
                          indexBuffer:mtl_index_buffer
                    indexBufferOffset:command.index_buffer.range.offset
@@ -524,7 +544,7 @@ static bool Bind(PassBindingsCache& pass,
                         baseInstance:0u];
     } else {
       [encoder drawIndexedPrimitives:ToMTLPrimitiveType(primitive_type)
-                          indexCount:command.index_count
+                          indexCount:command.vertex_count
                            indexType:ToMTLIndexType(command.index_type)
                          indexBuffer:mtl_index_buffer
                    indexBufferOffset:command.index_buffer.range.offset];

impeller/renderer/backend/vulkan/formats_vk.h

@@ -330,6 +330,8 @@ constexpr vk::IndexType ToVKIndexType(IndexType index_type) {
       return vk::IndexType::eUint32;
     case IndexType::kUnknown:
       return vk::IndexType::eUint32;
+    case IndexType::kNone:
+      FML_UNREACHABLE();
   }
 
   FML_UNREACHABLE();

impeller/renderer/backend/vulkan/render_pass_vk.cc

@@ -429,7 +429,7 @@ static bool EncodeCommand(const Context& context,
                           const Command& command,
                           CommandEncoderVK& encoder,
                           const ISize& target_size) {
-  if (command.index_count == 0u || command.instance_count == 0u) {
+  if (command.vertex_count == 0u || command.instance_count == 0u) {
     return true;
   }
 
@@ -466,24 +466,22 @@ static bool EncodeCommand(const Context& context,
 
   // Configure vertex and index and buffers for binding.
   auto vertex_buffer_view = command.GetVertexBuffer();
-  auto index_buffer_view = command.index_buffer;
 
-  if (!vertex_buffer_view || !index_buffer_view) {
+  if (!vertex_buffer_view) {
     return false;
   }
 
   auto& allocator = *context.GetResourceAllocator();
 
   auto vertex_buffer = vertex_buffer_view.buffer->GetDeviceBuffer(allocator);
-  auto index_buffer = index_buffer_view.buffer->GetDeviceBuffer(allocator);
 
-  if (!vertex_buffer || !index_buffer) {
-    VALIDATION_LOG << "Failed to acquire device buffers"
-                   << " for vertex and index buffer views";
+  if (!vertex_buffer) {
+    VALIDATION_LOG << "Failed to acquire device buffer"
+                   << " for vertex buffer view";
     return false;
   }
 
-  if (!encoder.Track(vertex_buffer) || !encoder.Track(index_buffer)) {
+  if (!encoder.Track(vertex_buffer)) {
     return false;
   }
 
@@ -493,19 +491,44 @@ static bool EncodeCommand(const Context& context,
   vk::DeviceSize vertex_buffer_offsets[] = {vertex_buffer_view.range.offset};
   cmd_buffer.bindVertexBuffers(0u, 1u, vertex_buffers, vertex_buffer_offsets);
 
-  // Bind the index buffer.
-  auto index_buffer_handle = DeviceBufferVK::Cast(*index_buffer).GetBuffer();
-  cmd_buffer.bindIndexBuffer(index_buffer_handle,
-                             index_buffer_view.range.offset,
-                             ToVKIndexType(command.index_type));
-
-  // Engage!
-  cmd_buffer.drawIndexed(command.index_count,     // index count
-                         command.instance_count,  // instance count
-                         0u,                      // first index
-                         command.base_vertex,     // vertex offset
-                         0u                       // first instance
-  );
+  if (command.index_type != IndexType::kNone) {
+    // Bind the index buffer.
+    auto index_buffer_view = command.index_buffer;
+    if (!index_buffer_view) {
+      return false;
+    }
+
+    auto index_buffer = index_buffer_view.buffer->GetDeviceBuffer(allocator);
+    if (!index_buffer) {
+      VALIDATION_LOG << "Failed to acquire device buffer"
+                     << " for index buffer view";
+      return false;
+    }
+
+    if (!encoder.Track(index_buffer)) {
+      return false;
+    }
+
+    auto index_buffer_handle = DeviceBufferVK::Cast(*index_buffer).GetBuffer();
+    cmd_buffer.bindIndexBuffer(index_buffer_handle,
+                               index_buffer_view.range.offset,
+                               ToVKIndexType(command.index_type));
+
+    // Engage!
+    cmd_buffer.drawIndexed(command.vertex_count,    // index count
+                           command.instance_count,  // instance count
+                           0u,                      // first index
+                           command.base_vertex,     // vertex offset
+                           0u                       // first instance
+    );
+  } else {
+    FML_LOG(ERROR) << "HERE!!!";
+    cmd_buffer.draw(command.vertex_count,    // vertex count
+                    command.instance_count,  // instance count
+                    command.base_vertex,     // vertex offset
+                    0u                       // first instance
+    );
+  }
   return true;
 }
 

impeller/renderer/command.cc

@@ -21,7 +21,7 @@ bool Command::BindVertices(const VertexBuffer& buffer) {
   vertex_bindings.buffers[VertexDescriptor::kReservedVertexBufferIndex] = {
       nullptr, buffer.vertex_buffer};
   index_buffer = buffer.index_buffer;
-  index_count = buffer.index_count;
+  vertex_count = buffer.vertex_count;
   index_type = buffer.index_type;
   return true;
 }