From 68d9c0537735f86050e327be483cc1e66469ef3c Mon Sep 17 00:00:00 2001
From: rhhong <rhhong@amazon.com>
Date: Tue, 26 Oct 2021 08:14:34 -0700
Subject: [PATCH] wireframe rendering

Signed-off-by: rhhong <rhhong@amazon.com>
Signed-off-by: Gene Walters <genewalt@amazon.com>
---
 .../Code/Source/AtomActorDebugDraw.cpp        | 76 +++++++++++++++++++
 .../Code/Source/AtomActorDebugDraw.h          |  1 +
 2 files changed, 77 insertions(+)

diff --git a/Gems/AtomLyIntegration/EMotionFXAtom/Code/Source/AtomActorDebugDraw.cpp b/Gems/AtomLyIntegration/EMotionFXAtom/Code/Source/AtomActorDebugDraw.cpp
index eaaf04fcf2..836e2c8822 100644
--- a/Gems/AtomLyIntegration/EMotionFXAtom/Code/Source/AtomActorDebugDraw.cpp
+++ b/Gems/AtomLyIntegration/EMotionFXAtom/Code/Source/AtomActorDebugDraw.cpp
@@ -88,6 +88,10 @@ namespace AZ::Render
                 {
                     RenderTangents(mesh, globalTM);
                 }
+                if (renderWireframe)
+                {
+                    RenderWireframe(mesh, globalTM);
+                }
             }
         }
     }
@@ -412,4 +416,76 @@ namespace AZ::Render
         lineArgs.m_depthTest = RPI::AuxGeomDraw::DepthTest::Off;
         auxGeom->DrawLines(lineArgs);
     }
+
+    // Render wireframe mesh
+    void AtomActorDebugDraw::RenderWireframe(EMotionFX::Mesh* mesh, const AZ::Transform& worldTM)
+    {
+        // Check if the mesh is valid and skip the node in case it's not
+        if (!mesh)
+        {
+            return;
+        }
+
+        RPI::AuxGeomDrawPtr auxGeom = m_auxGeomFeatureProcessor->GetDrawQueue();
+        if (!auxGeom)
+        {
+            return;
+        }
+
+        PrepareForMesh(mesh, worldTM);
+
+        const float scale = 0.01f;
+
+        AZ::Vector3* normals = (AZ::Vector3*)mesh->FindVertexData(EMotionFX::Mesh::ATTRIB_NORMALS);
+        const AZ::Color vertexColor = AZ::Color(0.8f, 0.24f, 0.88f, 1.0f);
+
+        const size_t numSubMeshes = mesh->GetNumSubMeshes();
+        for (uint32 subMeshIndex = 0; subMeshIndex < numSubMeshes; ++subMeshIndex)
+        {
+            EMotionFX::SubMesh* subMesh = mesh->GetSubMesh(subMeshIndex);
+            const uint32 numTriangles = subMesh->GetNumPolygons();
+            const uint32 startVertex = subMesh->GetStartVertex();
+            const uint32* indices = subMesh->GetIndices();
+
+            m_auxVertices.clear();
+            m_auxVertices.reserve(numTriangles * 6);
+            m_auxColors.clear();
+            m_auxColors.reserve(m_auxVertices.size());
+
+            for (uint32 triangleIndex = 0; triangleIndex < numTriangles; ++triangleIndex)
+            {
+                const uint32 triangleStartIndex = triangleIndex * 3;
+                const uint32 indexA = indices[triangleStartIndex + 0] + startVertex;
+                const uint32 indexB = indices[triangleStartIndex + 1] + startVertex;
+                const uint32 indexC = indices[triangleStartIndex + 2] + startVertex;
+
+                const AZ::Vector3 posA = m_worldSpacePositions[indexA] + normals[indexA] * scale;
+                const AZ::Vector3 posB = m_worldSpacePositions[indexB] + normals[indexB] * scale;
+                const AZ::Vector3 posC = m_worldSpacePositions[indexC] + normals[indexC] * scale;
+
+                m_auxVertices.emplace_back(posA);
+                m_auxColors.emplace_back(vertexColor);
+                m_auxVertices.emplace_back(posB);
+                m_auxColors.emplace_back(vertexColor);
+
+                m_auxVertices.emplace_back(posB);
+                m_auxColors.emplace_back(vertexColor);
+                m_auxVertices.emplace_back(posC);
+                m_auxColors.emplace_back(vertexColor);
+
+                m_auxVertices.emplace_back(posC);
+                m_auxColors.emplace_back(vertexColor);
+                m_auxVertices.emplace_back(posA);
+                m_auxColors.emplace_back(vertexColor);
+            }
+        }
+
+        RPI::AuxGeomDraw::AuxGeomDynamicDrawArguments lineArgs;
+        lineArgs.m_verts = m_auxVertices.data();
+        lineArgs.m_vertCount = static_cast<uint32_t>(m_auxVertices.size());
+        lineArgs.m_colors = m_auxColors.data();
+        lineArgs.m_colorCount = static_cast<uint32_t>(m_auxColors.size());
+        lineArgs.m_depthTest = RPI::AuxGeomDraw::DepthTest::Off;
+        auxGeom->DrawLines(lineArgs);
+    }
 } // namespace AZ::Render
diff --git a/Gems/AtomLyIntegration/EMotionFXAtom/Code/Source/AtomActorDebugDraw.h b/Gems/AtomLyIntegration/EMotionFXAtom/Code/Source/AtomActorDebugDraw.h
index 9f8b137f13..797de16351 100644
--- a/Gems/AtomLyIntegration/EMotionFXAtom/Code/Source/AtomActorDebugDraw.h
+++ b/Gems/AtomLyIntegration/EMotionFXAtom/Code/Source/AtomActorDebugDraw.h
@@ -43,6 +43,7 @@ namespace AZ::Render
         void RenderEMFXDebugDraw(EMotionFX::ActorInstance* instance);
         void RenderNormals(EMotionFX::Mesh* mesh, const AZ::Transform& worldTM, bool vertexNormals, bool faceNormals);
         void RenderTangents(EMotionFX::Mesh* mesh, const AZ::Transform& worldTM);
+        void RenderWireframe(EMotionFX::Mesh* mesh, const AZ::Transform& worldTM);
 
         EMotionFX::Mesh* m_currentMesh = nullptr; /**< A pointer to the mesh whose world space positions are in the pre-calculated positions buffer.
                                            NULL in case we haven't pre-calculated any positions yet. */