feat(collider): add mesh collider support and related debug drawing functionality

Author: AhmedAmrNabil

src/game/components/collider.cpp

@@ -1,8 +1,11 @@
 #include "collider.hpp"
 
+#include "asset-loader.hpp"
+
 static gameplay::ColliderShape parseColliderShape(const std::string& value, gameplay::ColliderShape fallback) {
     if (value == "Sphere") return gameplay::ColliderShape::Sphere;
     if (value == "Capsule") return gameplay::ColliderShape::Capsule;
+    if (value == "Mesh" || value == "Model") return gameplay::ColliderShape::Mesh;
     return fallback;
 }
 
@@ -24,6 +27,33 @@ namespace gameplay {
         isTrigger = data.value("isTrigger", isTrigger);
         std::string stringLayer = data.value("layer", "");
         layer = layerStringToGroup(stringLayer);
+        std::string modelName = data.value("model", "");
+        std::string meshName =
+            data.value("mesh", "");  // "mesh" is an alternative key for the model name, in case "model" is not provided
+        if (!modelName.empty()) {
+            our::Model* model = our::AssetLoader<our::Model>::get(modelName);
+            if (model) {
+                std::cout << "Loaded model for collider: " << modelName << std::endl;
+                mesh = model->getCombinedMesh();
+            }
+            if (!mesh) {
+                std::cerr << "\033[31mFailed to load model for collider: " << modelName << "\033[0m" << std::endl;
+            }
+        } else if (!meshName.empty()) {
+            our::Mesh* assetMesh = our::AssetLoader<our::Mesh>::get(meshName);
+            if (assetMesh) {
+                mesh = assetMesh;
+            }
+            if (!mesh) {
+                std::cerr << "\033[31mFailed to load mesh for collider: " << meshName << "\033[0m" << std::endl;
+            }
+        }
+    }
+
+    ColliderComponent::~ColliderComponent() {
+        if (shape == ColliderShape::Mesh && bulletMesh) {
+            delete bulletMesh;
+        }
     }
 
 }  // namespace gameplay

src/game/components/collider.hpp

@@ -1,10 +1,14 @@
 #pragma once
 
 #include <ecs/component.hpp>
+#include <glm/glm.hpp>
+#include <model/model.hpp>
+
+#include "bullet/BulletCollision/CollisionShapes/btTriangleMesh.h"
 
 namespace gameplay {
 
-    enum class ColliderShape { Sphere, Capsule };
+    enum class ColliderShape { Sphere, Capsule, Mesh };
 
     enum CollisionLayer : short {
         LAYER_PLAYER = 1 << 0,       // bit 0:  0000 0001
@@ -21,12 +25,16 @@ namespace gameplay {
         float radius = 0.5f;
         float height = 1.0f;  // must be the total height
         bool isTrigger = false;
+        our::Mesh* mesh = nullptr;  // optional mesh for mesh colliders
+        btTriangleMesh* bulletMesh =
+            nullptr;  // owned by ColliderComponent, freed in destructor (only used if shape == Mesh)
 
         static std::string getID() {
             return "Collider";
         }
 
         void deserialize(const nlohmann::json& data) override;
+        ~ColliderComponent();
     };
 
 }  // namespace gameplay

src/game/systems/collision-debug-drawer.cpp

@@ -37,6 +37,24 @@ out vec4 fragColor;
 void main() {
     fragColor = vec4(vColor, 1.0);
 }
+)";
+
+    static const char* kMeshVertexShader = R"(
+#version 330 core
+layout(location = 0) in vec3 aPos;
+uniform mat4 uMVP;
+void main() {
+    gl_Position = uMVP * vec4(aPos, 1.0);
+}
+)";
+
+    static const char* kMeshFragmentShader = R"(
+#version 330 core
+uniform vec3 uColor;
+out vec4 fragColor;
+void main() {
+    fragColor = vec4(uColor, 1.0);
+}
 )";
 
     // ---- Helper: compile a single shader stage ----
@@ -77,6 +95,29 @@ void main() {
         glDeleteShader(frag);
 
         vpUniformLoc = glGetUniformLocation(shaderProgram, "uVP");
+
+        // Mesh shader program
+        GLuint mVert = compileShaderStage(GL_VERTEX_SHADER, kMeshVertexShader);
+        GLuint mFrag = compileShaderStage(GL_FRAGMENT_SHADER, kMeshFragmentShader);
+
+        meshShaderProgram = glCreateProgram();
+        glAttachShader(meshShaderProgram, mVert);
+        glAttachShader(meshShaderProgram, mFrag);
+        glLinkProgram(meshShaderProgram);
+
+        success = 0;
+        glGetProgramiv(meshShaderProgram, GL_LINK_STATUS, &success);
+        if (!success) {
+            char log[512];
+            glGetProgramInfoLog(meshShaderProgram, sizeof(log), nullptr, log);
+            fprintf(stderr, "[CollisionDebugDrawer] Mesh Shader link error:\n%s\n", log);
+        }
+
+        glDeleteShader(mVert);
+        glDeleteShader(mFrag);
+
+        meshMVPUniformLoc = glGetUniformLocation(meshShaderProgram, "uMVP");
+        meshColorUniformLoc = glGetUniformLocation(meshShaderProgram, "uColor");
     }
 
     void CollisionDebugDrawer::initialize() {
@@ -115,7 +156,12 @@ void main() {
             glDeleteProgram(shaderProgram);
             shaderProgram = 0;
         }
+        if (meshShaderProgram) {
+            glDeleteProgram(meshShaderProgram);
+            meshShaderProgram = 0;
+        }
         lineVertices.clear();
+        meshDrawCommands.clear();
     }
 
     // ---- Wireframe generation helpers ----
@@ -213,6 +259,10 @@ void main() {
         }
     }
 
+    void CollisionDebugDrawer::drawMeshWireframe(our::Mesh* mesh, const glm::mat4& transform, const glm::vec3& color) {
+        meshDrawCommands.push_back({mesh, transform, color});
+    }
+
     // ---- btIDebugDraw overrides (still needed since Bullet requires them) ----
     void CollisionDebugDrawer::drawLine(const btVector3& from, const btVector3& to, const btVector3& color) {
         lineVertices.push_back({from.getX(), from.getY(), from.getZ(), color.getX(), color.getY(), color.getZ()});
@@ -243,6 +293,23 @@ void main() {
 
         glUseProgram(0);
 
+        // Render meshes if any
+        if (!meshDrawCommands.empty()) {
+            glUseProgram(meshShaderProgram);
+            glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+
+            for (const auto& cmd : meshDrawCommands) {
+                glm::mat4 MVP = VP * cmd.transform;
+                glUniformMatrix4fv(meshMVPUniformLoc, 1, GL_FALSE, glm::value_ptr(MVP));
+                glUniform3fv(meshColorUniformLoc, 1, glm::value_ptr(cmd.color));
+                cmd.mesh->draw();
+            }
+
+            glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
+            glUseProgram(0);
+            meshDrawCommands.clear();
+        }
+
         // Restore previous state
         if (prevDepthTest) glEnable(GL_DEPTH_TEST);
 

src/game/systems/collision-debug-drawer.hpp

@@ -6,6 +6,7 @@
 #include <glad/gl.h>
 
 #include <glm/glm.hpp>
+#include <mesh/mesh.hpp>
 #include <vector>
 
 namespace gameplay {
@@ -21,6 +22,7 @@ namespace gameplay {
         // ---- Manual wireframe generators (used instead of Bullet's debugDrawObject) ----
         void drawSphereWireframe(const glm::mat4& transform, float radius, const glm::vec3& color);
         void drawCapsuleWireframe(const glm::mat4& transform, float radius, float totalHeight, const glm::vec3& color);
+        void drawMeshWireframe(our::Mesh* mesh, const glm::mat4& transform, const glm::vec3& color);
 
         // ---- btIDebugDraw overrides (required by interface) ----
         void drawLine(const btVector3& from, const btVector3& to, const btVector3& color) override;
@@ -42,11 +44,22 @@ namespace gameplay {
 
         std::vector<LineVertex> lineVertices;
 
+        struct MeshDrawCommand {
+            our::Mesh* mesh;
+            glm::mat4 transform;
+            glm::vec3 color;
+        };
+        std::vector<MeshDrawCommand> meshDrawCommands;
+
         GLuint vao = 0;
         GLuint vbo = 0;
         GLuint shaderProgram = 0;
         GLint vpUniformLoc = -1;
 
+        GLuint meshShaderProgram = 0;
+        GLint meshMVPUniformLoc = -1;
+        GLint meshColorUniformLoc = -1;
+
         int debugMode = DBG_DrawWireframe;
 
         void createShader();

src/game/systems/collision-system.cpp

@@ -295,6 +295,26 @@ namespace gameplay {
                     shape = new btCapsuleShape(collider->radius, spine);
                     break;
                 }
+                case ColliderShape::Mesh:
+                    if (collider->mesh) {
+                        collider->bulletMesh = new btTriangleMesh();
+                        const std::vector<our::Vertex>& vertices = collider->mesh->getVertices();
+                        const std::vector<unsigned int>& indices = collider->mesh->getIndices();
+                        collider->bulletMesh->preallocateVertices(vertices.size());
+                        collider->bulletMesh->preallocateIndices(indices.size());
+                        for (size_t i = 0; i < indices.size(); i += 3) {
+                            const glm::vec3& v0 = vertices[indices[i]].position;
+                            const glm::vec3& v1 = vertices[indices[i + 1]].position;
+                            const glm::vec3& v2 = vertices[indices[i + 2]].position;
+                            collider->bulletMesh->addTriangle(glmToBtVec3(v0), glmToBtVec3(v1), glmToBtVec3(v2));
+                        }
+                        shape = new btBvhTriangleMeshShape(collider->bulletMesh, true);
+                    } else {
+                        std::cerr << "\033[31mCollider mesh is null for entity " << entity->name
+                                  << ". Defaulting to sphere shape.\033[0m" << std::endl;
+                        shape = new btSphereShape(collider->radius);
+                    }
+                    break;
             }
             shape->setLocalScaling(glmToBtVec3(entity->localTransform.scale));
             shapesCache[shapeKey] = shape;
@@ -411,6 +431,7 @@ namespace gameplay {
             btVector3 scale = obj->getCollisionShape()->getLocalScaling();
             float scaledRadius = collider->radius * scale.getX();
             float scaledHeight = collider->height * scale.getY();
+            transform = transform * glm::scale(glm::mat4(1.0f), glm::vec3(scale.getX(), scale.getY(), scale.getZ()));
 
             switch (collider->shape) {
                 case ColliderShape::Sphere:
@@ -419,6 +440,11 @@ namespace gameplay {
                 case ColliderShape::Capsule:
                     debugDrawer->drawCapsuleWireframe(transform, scaledRadius, scaledHeight, color);
                     break;
+                case ColliderShape::Mesh:
+                    if (collider->mesh) {
+                        debugDrawer->drawMeshWireframe(collider->mesh, transform, color);
+                    }
+                    break;
             }
         }