feat: instance + array buffer

engine/include/engine/components/batch.h

@@ -2,12 +2,15 @@
 #define COMPONENT_BATCH_H_
 
 #include <glm/mat4x4.hpp>
+#include <memory>
+
+#include "engine/opengl/buffers.h"
+
 #include "engine/export.h"
 
 namespace Core {
 // requires mesh component
 struct ENGINE_API batch {
-    friend class Renderer;
 public:
     // requires Transform component
     struct item {
@@ -17,13 +20,18 @@ public:
     batch();
 
     inline const unsigned int id() const { return m_id; }
+    inline const bool Initialized() const { return m_instanceBuffer != nullptr; }
 protected:
     static unsigned int LastID;
 private:
     unsigned int m_id;
     unsigned int m_instance_vbo { 0 };
     unsigned int m_instance_count { 0 };
+
+    // TODO: use static draw when possible
+    std::unique_ptr<OpenGL::InstanceBuffer> m_instanceBuffer = nullptr;
 private:
+    friend class Renderer;
     void prepare(glm::mat4 *instances, unsigned int count);
 };
 }

engine/include/engine/opengl/buffers.h

@@ -17,15 +17,16 @@ namespace OpenGL {
     public:
         Buffer(BufferTarget target, BufferUsage usage);
 
+        inline const BufferID GetID() const { return m_buffer; }
     protected:
         void Data(void* data, size_t size);
         void SubData(void *data, size_t size, size_t offset);
         
-        void BindBuffer(unsigned int index);
+        void BindBuffer(unsigned int index) const;
-        void BindBufferRanged(unsigned int index, size_t offset, size_t size);
+        void BindBufferRanged(unsigned int index, size_t offset, size_t size) const;
     protected:
-        void Bind();
+        void Bind() const;
-        void Unbind();
+        void Unbind() const;
     private:
         BufferID m_buffer;
         BufferTarget m_target;
@@ -36,7 +37,7 @@ namespace OpenGL {
     public:
         UniformBuffer(size_t size, unsigned int index);
 
-        void ConfigureShader(Shader& shader, const char* uniformName);
+        void ConfigureShader(Shader& shader, const char* uniformName) const;
 
         template<typename T, typename S = size_t>
         void UpdateUniform(void* data, S offset) {
@@ -47,6 +48,27 @@ namespace OpenGL {
     private:
         static unsigned int s_bufferNextId;
     };
+
+    class ENGINE_API ArrayBuffer : public Buffer {
+    public:
+        ArrayBuffer(BufferUsage usage);
+    };
+
+    class ENGINE_API InstanceBuffer : public ArrayBuffer {
+    public:
+        InstanceBuffer(BufferUsage usage);
+
+        void Data(void *data, size_t size) {
+            Buffer::Data(data, size);
+        }
+
+        void SubData(void *data, size_t size, size_t offset) {
+            Buffer::SubData(data, size, offset);
+        }
+
+        inline void StartConfigure() const { Bind(); }
+        inline void EndConfigure() const { Unbind(); }
+    };
 } // namespace OpenGL
 
 } // namespace Core

engine/include/engine/renderer/wavefront.h

@@ -11,6 +11,7 @@
 #include "engine/renderer/renderer.h"
 #include "engine/renderer/material.h"
 #include "engine/renderer/mesh.h"
+#include "engine/opengl/buffers.h"
 
 #include "engine/export.h"
 
@@ -43,7 +44,7 @@ public:
     void Render(Shader& shader, unsigned int count);
     [[nodiscard]] inline const std::string Name() const { return m_name; }
 protected:
-    void EnableBatch(unsigned int instanceVBO);
+    void EnableBatch(const OpenGL::InstanceBuffer* instanceBuffer);
 private:
     std::string m_name;
     std::vector<glm::vec3> m_vertices;

engine/src/components/batch.cpp

@@ -11,24 +11,19 @@ batch::batch() {
 }
 
 void batch::prepare(glm::mat4 *instances, unsigned int count) {
-    if (m_instance_vbo == 0) {
+    if (!m_instanceBuffer) {
-        glGenBuffers(1, &m_instance_vbo);
+        m_instanceBuffer = std::make_unique<OpenGL::InstanceBuffer>(GL_DYNAMIC_DRAW);
-        glBindBuffer(GL_ARRAY_BUFFER, m_instance_vbo);
+        m_instanceBuffer->Data(nullptr, sizeof(glm::mat4) * count);
-        // Allocate *once*, no data yet — just reserve space
-        glBufferData(GL_ARRAY_BUFFER, sizeof(glm::mat4) * count, nullptr, GL_DYNAMIC_DRAW);
         m_instance_count = count;
     } else if (count > m_instance_count) {
         // Optional: reallocate only if you *really* have more instances than before
         glBindBuffer(GL_ARRAY_BUFFER, m_instance_vbo);
-        glBufferData(GL_ARRAY_BUFFER, sizeof(glm::mat4) * count, nullptr, GL_DYNAMIC_DRAW);
+        m_instanceBuffer->Data(nullptr, sizeof(glm::mat4) * count);
         m_instance_count = count;
-    } else {
-        glBindBuffer(GL_ARRAY_BUFFER, m_instance_vbo);
     }
 
     // Just update the data region — much cheaper
-    glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(glm::mat4) * count, instances);
+    m_instanceBuffer->SubData(instances, sizeof(glm::mat4) * count, 0);
-    glBindBuffer(GL_ARRAY_BUFFER, 0);
 }
 
 }

engine/src/opengl/buffers.cpp

@@ -13,11 +13,11 @@ namespace OpenGL {
         Unbind();
     }
 
-    void Buffer::Bind() {
+    void Buffer::Bind() const {
         glBindBuffer(m_target, m_buffer);
     }
 
-    void Buffer::Unbind() {
+    void Buffer::Unbind() const {
         glBindBuffer(m_target, 0);
     }
 
@@ -33,13 +33,13 @@ namespace OpenGL {
         Unbind();
     }
 
-    void Buffer::BindBuffer(unsigned int index) {
+    void Buffer::BindBuffer(unsigned int index) const {
         Bind();
         glBindBufferBase(m_target, index, m_buffer);
         Unbind();
     }
 
-    void Buffer::BindBufferRanged(unsigned int index, size_t offset, size_t size) {
+    void Buffer::BindBufferRanged(unsigned int index, size_t offset, size_t size) const {
         Bind();
         glBindBufferRange(m_target, index, m_buffer, offset, size);
         Unbind();
@@ -55,11 +55,17 @@ namespace OpenGL {
         BindBuffer(m_uniformBinding);
     }
 
-    void UniformBuffer::ConfigureShader(Shader& shader, const char* uniformName) {
+    void UniformBuffer::ConfigureShader(Shader& shader, const char* uniformName) const {
         auto uniformIndex = glGetUniformBlockIndex(shader.GetID(), uniformName);
         glUniformBlockBinding(shader.GetID(), uniformIndex, m_uniformBinding);
     }
 
+    ArrayBuffer::ArrayBuffer(BufferUsage usage)
+        : Buffer(GL_ARRAY_BUFFER, usage) {}
+    
+    InstanceBuffer::InstanceBuffer(BufferUsage usage)
+        : ArrayBuffer(usage) {}
+
 } // namespace OpenGL
 
 } // namespace Core

engine/src/renderer/renderer.cpp

@@ -166,11 +166,11 @@ void Renderer::RenderScene(Shader &shader) {
             models.push_back(itemModel);
         }
 
-        auto prevInstanceVBO = b.m_instance_vbo;
+        auto prevState = b.Initialized();
         b.prepare(models.data(), models.size());
-        if (prevInstanceVBO <= 0) {
+        if (!prevState) {
             std::cout << "[DEBUG] enabling batch" << std::endl;
-            m.object->EnableBatch(b.m_instance_vbo);
+            m.object->EnableBatch(b.m_instanceBuffer.get());
         }
         m.object->Render(shader, batchItems.size());
     }

engine/src/renderer/wavefront.cpp

@@ -397,11 +397,11 @@ Object* Object::LoadFile(const std::string& filename) {
     return obj;
 }
 
-void Object::EnableBatch(unsigned int instanceVBO) {
+void Object::EnableBatch(const OpenGL::InstanceBuffer* instanceBuffer) {
     for (auto &mesh : m_meshes) {
         mesh.Bind();
 
-        glBindBuffer(GL_ARRAY_BUFFER, instanceVBO);
+        instanceBuffer->StartConfigure();
             std::size_t vec4Size = sizeof(glm::vec4);
             for (int i = 0; i < 4; ++i) {
                 glEnableVertexAttribArray(3 + i); // use locations 3,4,5,6 for instance matrix
@@ -409,7 +409,7 @@ void Object::EnableBatch(unsigned int instanceVBO) {
                                     sizeof(glm::mat4), (void*)(i * vec4Size));
                 glVertexAttribDivisor(3 + i, 1); // IMPORTANT: one per instance, not per vertex
             }
-        glBindBuffer(GL_ARRAY_BUFFER, 0);
+        instanceBuffer->EndConfigure();
         
         mesh.Unbind();
     }