“Yeah It’s on. ”
前言
周末对游戏引擎HXEngine进行了简单的场景管理及动态批处理。后续考虑进行八叉树管理及静态drawcall合并。
正文
#总体思路：
首选在编辑器或者配置文件中为所有场景中gameobject的submesh的renderable的material配置一个render queue值，值越小就越先渲染。这里大致分为几类：
enum ERenderQueue
{
RQ_BACKGROUND = 1000,
RQ_GEOMETRY = 2000,
RQ_ALPHATEST = 2450,
RQ_TRANSPARENT = 3000,
RQ_OVERLAY = 4000
};
然后根据是否需要alpha blend(render queue == 3000 为分界线)，把material分为两大类opaque和transparent。分别将gameobject的submesh对应的可渲染单位放入相应的列表中。
- opaque以render queue为key，把相同render queue下相同材质的renderable放入到一个队列中，每帧渲染时这个队列就作为一个batch，只需设置一次材质状态。
- transparent以render queue为key，把相同render queue的renderable放入到一个队列中，每帧渲染时需要对这个队列按同相机距离从远到近排序。把相邻的相同材质的renderable作为一个batch，顺序渲染。
#具体实现：
场景管理器中的数据结构如下：
// gameobject tree root
HXGameObject* gameObjectTreeRoot;
typedef std::vector<HXRenderable*> vectorRenderable;
typedef std::map<std::string, vectorRenderable> mapStringVector;
// opaque
std::map<int, mapStringVector> opaqueMap;
// transparent
std::map<int, vectorRenderable> transparentMap;
gameObjectTreeRoot为gameobject树状结构根节点，用于具体管理场景中的gameobject(查询、创建、删除等)。
按上述思路根据gameObjectTree创建opaqueMap和transparentMap用于渲染。
具体渲染过程：
void HXSceneManager::OnDisplay(bool shadow)
{
if (!mainCamera)
{
return;
}
HXRenderSystem* pRenderSystem = HXRoot::GetInstance()->GetRenderSystem();
if (NULL == pRenderSystem)
{
return;
}
if (shadow)
{
HXStatus::GetInstance()->ResetStatus();
mainCamera->Update();
gameObjectTreeRoot->Update();
}
// render opaque
HXMaterial* curMaterial = NULL;
for (std::map<int, mapStringVector>::iterator itr = opaqueMap.begin(); itr != opaqueMap.end(); ++itr)
{
for (mapStringVector::iterator itr1 = itr->second.begin(); itr1 != itr->second.end(); ++itr1)
{
for (vectorRenderable::iterator itr2 = itr1->second.begin(); itr2 != itr1->second.end(); ++itr2)
{
HXRenderable* renderable = *itr2;
if (shadow && !renderable->m_pSubMesh->IsCastShadow)
{
continue;
}
if (curMaterial != renderable->m_pMaterial)
{
curMaterial = renderable->m_pMaterial;
if (shadow)
{
curMaterial->SetShadowMapMaterialRenderStateAllRenderable();
}
else
{
curMaterial->SetMaterialRenderStateAllRenderable();
}
}
HXStatus::GetInstance()->nVertexCount += renderable->m_pSubMesh->vertexList.size();
HXStatus::GetInstance()->nTriangleCount += renderable->m_pSubMesh->triangleCount;
renderable->SetModelMatrix(renderable->m_pTransform->mCurModelMatrix);
renderable->SetViewMatrix(mainCamera);
renderable->SetProjectionMatrix(mainCamera);
if (shadow)
{
curMaterial->SetShadowMapMaterialRenderStateEachRenderable(renderable);
}
else
{
curMaterial->SetMaterialRenderStateEachRenderable(renderable);
}
pRenderSystem->RenderSingle(renderable, shadow);
}
}
}
curMaterial = NULL;
// render transparent
// Z排序
if (shadow)
{
for (std::map<int, vectorRenderable>::iterator itr = transparentMap.begin(); itr != transparentMap.end(); ++itr)
{
for (vectorRenderable::iterator itr1 = itr->second.begin(); itr1 != itr->second.end(); ++itr1)
{
HXRenderable* renderable = *itr1;
renderable->SetModelMatrix(renderable->m_pTransform->mCurModelMatrix);
renderable->SetViewMatrix(mainCamera);
renderable->SetProjectionMatrix(mainCamera);
}
}
for (std::map<int, vectorRenderable>::iterator itr = transparentMap.begin(); itr != transparentMap.end(); ++itr)
{
std::sort(itr->second.begin(), itr->second.end(), Zcompare);
}
}
curMaterial = NULL;
for (std::map<int, vectorRenderable>::iterator itr = transparentMap.begin(); itr != transparentMap.end(); ++itr)
{
for (vectorRenderable::iterator itr1 = itr->second.begin(); itr1 != itr->second.end(); ++itr1)
{
HXRenderable* renderable = *itr1;
if (shadow && !renderable->m_pSubMesh->IsCastShadow)
{
continue;
}
if (curMaterial != renderable->m_pMaterial)
{
curMaterial = renderable->m_pMaterial;
if (shadow)
{
curMaterial->SetShadowMapMaterialRenderStateAllRenderable();
}
else
{
curMaterial->SetMaterialRenderStateAllRenderable();
}
}
HXStatus::GetInstance()->nVertexCount += renderable->m_pSubMesh->vertexList.size();
HXStatus::GetInstance()->nTriangleCount += renderable->m_pSubMesh->triangleCount;
if (shadow)
{
curMaterial->SetShadowMapMaterialRenderStateEachRenderable(renderable);
}
else
{
curMaterial->SetMaterialRenderStateEachRenderable(renderable);
}
pRenderSystem->RenderSingle(renderable, shadow);
}
}
curMaterial = NULL;
if (!shadow)
{
HXStatus::GetInstance()->ShowStatusInfo();
}
}
后记
注意：每帧渲染时shader uniform的texture变量需要重新处理（赋值的只是纹理绑定点，纹理绑定点绑定的纹理可能被改掉了）
GLint tex_uniform_loc = glGetUniformLocation(render_scene_prog, (itr->name).c_str());
if (tex_uniform_loc == -1)
{
// 未参被实际调用的变量编译后会被自动删除
continue;
}
HXGLTexture* tex = (HXGLTexture*)HXResourceManager::GetInstance()->GetTexture("GL_" + itr->value);
glUniform1i(tex_uniform_loc, nTexIndex);
glActiveTexture(GL_TEXTURE0 + nTexIndex);
glBindTexture(GL_TEXTURE_2D, tex->texId);
后续考虑：
进行静态批处理，把静态物体提前生成到同一个vbo中以合并drawcall。
GameObjectTree进行八叉树管理等
