Merge 'remotes/trunk'

[0ad.git] / source / renderer / VertexBuffer.cpp

/* Copyright (C) 2022 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "precompiled.h"

#include "VertexBuffer.h"

#include "lib/sysdep/cpu.h"
#include "ps/CLogger.h"
#include "ps/Errors.h"
#include "ps/VideoMode.h"
#include "renderer/backend/IDevice.h"
#include "renderer/Renderer.h"

#include <algorithm>
#include <cstring>
#include <iterator>

// Absolute maximum (bytewise) size of each GL vertex buffer object.
// Make it large enough for the maximum feasible mesh size (64K vertexes,
// 64 bytes per vertex in InstancingModelRenderer).
// TODO: measure what influence this has on performance
constexpr std::size_t MAX_VB_SIZE_BYTES = 4 * 1024 * 1024;

CVertexBuffer::CVertexBuffer(
        const char* name, const size_t vertexSize,
        const Renderer::Backend::IBuffer::Type type, const bool dynamic)
        : CVertexBuffer(name, vertexSize, type, dynamic, MAX_VB_SIZE_BYTES)
{
}

CVertexBuffer::CVertexBuffer(
        const char* name, const size_t vertexSize,
        const Renderer::Backend::IBuffer::Type type, const bool dynamic,
        const size_t maximumBufferSize)
        : m_VertexSize(vertexSize), m_HasNeededChunks(false)
{
        size_t size = maximumBufferSize;

        if (type == Renderer::Backend::IBuffer::Type::VERTEX)
        {
                // We want to store 16-bit indices to any vertex in a buffer, so the
                // buffer must never be bigger than vertexSize*64K bytes since we can
                // address at most 64K of them with 16-bit indices
                size = std::min(size, vertexSize * 65536);
        }
        else if (type == Renderer::Backend::IBuffer::Type::INDEX)
        {
                ENSURE(vertexSize == sizeof(u16));
        }

        // store max/free vertex counts
        m_MaxVertices = m_FreeVertices = size / vertexSize;

        m_Buffer = g_VideoMode.GetBackendDevice()->CreateBuffer(
                name, type, m_MaxVertices * m_VertexSize, dynamic);

        // create sole free chunk
        VBChunk* chunk = new VBChunk;
        chunk->m_Owner = this;
        chunk->m_Count = m_FreeVertices;
        chunk->m_Index = 0;
        m_FreeList.emplace_back(chunk);
}

CVertexBuffer::~CVertexBuffer()
{
        // Must have released all chunks before destroying the buffer
        ENSURE(m_AllocList.empty());

        m_Buffer.reset();

        for (VBChunk* const& chunk : m_FreeList)
                delete chunk;
}

bool CVertexBuffer::CompatibleVertexType(
        const size_t vertexSize, const Renderer::Backend::IBuffer::Type type,
        const bool dynamic) const
{
        ENSURE(m_Buffer);
        return type == m_Buffer->GetType() && dynamic == m_Buffer->IsDynamic() && vertexSize == m_VertexSize;
}

///////////////////////////////////////////////////////////////////////////////
// Allocate: try to allocate a buffer of given number of vertices (each of
// given size), with the given type, and using the given texture - return null
// if no free chunks available
CVertexBuffer::VBChunk* CVertexBuffer::Allocate(
        const size_t vertexSize, const size_t numberOfVertices,
        const Renderer::Backend::IBuffer::Type type, const bool dynamic,
        void* backingStore)
{
        // check this is the right kind of buffer
        if (!CompatibleVertexType(vertexSize, type, dynamic))
                return nullptr;

        if (UseStreaming(dynamic))
                ENSURE(backingStore != nullptr);

        // quick check there's enough vertices spare to allocate
        if (numberOfVertices > m_FreeVertices)
                return nullptr;

        // trawl free list looking for first free chunk with enough space
        std::vector<VBChunk*>::iterator best_iter = m_FreeList.end();
        for (std::vector<VBChunk*>::iterator iter = m_FreeList.begin(); iter != m_FreeList.end(); ++iter)
        {
                if (numberOfVertices == (*iter)->m_Count)
                {
                        best_iter = iter;
                        break;
                }
                else if (numberOfVertices < (*iter)->m_Count && (best_iter == m_FreeList.end() || (*best_iter)->m_Count < (*iter)->m_Count))
                        best_iter = iter;
        }

        // We could not find a large enough chunk.
        if (best_iter == m_FreeList.end())
                return nullptr;

        VBChunk* chunk = *best_iter;
        m_FreeList.erase(best_iter);
        m_FreeVertices -= chunk->m_Count;

        chunk->m_BackingStore = backingStore;
        chunk->m_Dirty = false;
        chunk->m_Needed = false;

        // split chunk into two; - allocate a new chunk using all unused vertices in the
        // found chunk, and add it to the free list
        if (chunk->m_Count > numberOfVertices)
        {
                VBChunk* newchunk = new VBChunk;
                newchunk->m_Owner = this;
                newchunk->m_Count = chunk->m_Count - numberOfVertices;
                newchunk->m_Index = chunk->m_Index + numberOfVertices;
                m_FreeList.emplace_back(newchunk);
                m_FreeVertices += newchunk->m_Count;

                // resize given chunk
                chunk->m_Count = numberOfVertices;
        }

        // return found chunk
        m_AllocList.push_back(chunk);
        return chunk;
}

///////////////////////////////////////////////////////////////////////////////
// Release: return given chunk to this buffer
void CVertexBuffer::Release(VBChunk* chunk)
{
        // Update total free count before potentially modifying this chunk's count
        m_FreeVertices += chunk->m_Count;

        m_AllocList.erase(std::find(m_AllocList.begin(), m_AllocList.end(), chunk));

        // Sorting O(nlogn) shouldn't be too far from O(n) by performance, because
        // the container is partly sorted already.
        std::sort(
                m_FreeList.begin(), m_FreeList.end(),
                [](const VBChunk* chunk1, const VBChunk* chunk2) -> bool
                {
                        return chunk1->m_Index < chunk2->m_Index;
                });

        // Coalesce with any free-list items that are adjacent to this chunk;
        // merge the found chunk with the new one, and remove the old one
        // from the list.
        for (std::vector<VBChunk*>::iterator iter = m_FreeList.begin(); iter != m_FreeList.end();)
        {
                if ((*iter)->m_Index == chunk->m_Index + chunk->m_Count
                 || (*iter)->m_Index + (*iter)->m_Count == chunk->m_Index)
                {
                        chunk->m_Index = std::min(chunk->m_Index, (*iter)->m_Index);
                        chunk->m_Count += (*iter)->m_Count;
                        delete *iter;
                        iter = m_FreeList.erase(iter);
                        if (!m_FreeList.empty() && iter != m_FreeList.begin())
                                iter = std::prev(iter);
                }
                else
                {
                        ++iter;
                }
        }

        m_FreeList.emplace_back(chunk);
}

///////////////////////////////////////////////////////////////////////////////
// UpdateChunkVertices: update vertex data for given chunk
void CVertexBuffer::UpdateChunkVertices(VBChunk* chunk, void* data)
{
        ENSURE(m_Buffer);
        if (UseStreaming(m_Buffer->IsDynamic()))
        {
                // The backend buffer is now out of sync with the backing store.
                chunk->m_Dirty = true;

                // Sanity check: Make sure the caller hasn't tried to reallocate
                // their backing store.
                ENSURE(data == chunk->m_BackingStore);
        }
        else
        {
                ENSURE(data);
                g_Renderer.GetDeviceCommandContext()->UploadBufferRegion(
                        m_Buffer.get(), data, chunk->m_Index * m_VertexSize, chunk->m_Count * m_VertexSize);
        }
}

void CVertexBuffer::UploadIfNeeded(
        Renderer::Backend::IDeviceCommandContext* deviceCommandContext)
{
        if (UseStreaming(m_Buffer->IsDynamic()))
        {
                if (!m_HasNeededChunks)
                        return;

                // If any chunks are out of sync with the current backend buffer, and are
                // needed for rendering this frame, we'll need to re-upload the backend buffer.
                bool needUpload = false;
                for (VBChunk* const& chunk : m_AllocList)
                {
                        if (chunk->m_Dirty && chunk->m_Needed)
                        {
                                needUpload = true;
                                break;
                        }
                }

                if (needUpload)
                {
                        deviceCommandContext->UploadBuffer(m_Buffer.get(), [&](u8* mappedData)
                        {
#ifndef NDEBUG
                                // To help detect bugs where PrepareForRendering() was not called,
                                // force all not-needed data to 0, so things won't get rendered
                                // with undefined (but possibly still correct-looking) data.
                                memset(mappedData, 0, m_MaxVertices * m_VertexSize);
#endif

                                // Copy only the chunks we need. (This condition is helpful when
                                // the backend buffer contains data for every unit in the world,
                                // but only a handful are visible on screen and we don't need to
                                // bother copying the rest.)
                                for (VBChunk* const& chunk : m_AllocList)
                                        if (chunk->m_Needed)
                                                std::memcpy(mappedData + chunk->m_Index * m_VertexSize, chunk->m_BackingStore, chunk->m_Count * m_VertexSize);
                        });

                        // Anything we just uploaded is clean; anything else is dirty
                        // since the rest of the backend buffer content is now undefined
                        for (VBChunk* const& chunk : m_AllocList)
                        {
                                if (chunk->m_Needed)
                                {
                                        chunk->m_Dirty = false;
                                        chunk->m_Needed = false;
                                }
                                else
                                        chunk->m_Dirty = true;
                        }
                }
                else
                {
                        // Reset the flags for the next phase.
                        for (VBChunk* const& chunk : m_AllocList)
                                chunk->m_Needed = false;
                }

                m_HasNeededChunks = false;
        }
}

size_t CVertexBuffer::GetBytesReserved() const
{
        return MAX_VB_SIZE_BYTES;
}

size_t CVertexBuffer::GetBytesAllocated() const
{
        return (m_MaxVertices - m_FreeVertices) * m_VertexSize;
}

void CVertexBuffer::DumpStatus() const
{
        debug_printf("freeverts = %d\n", static_cast<int>(m_FreeVertices));

        size_t maxSize = 0;
        for (VBChunk* const& chunk : m_FreeList)
        {
                debug_printf("free chunk %p: size=%d\n", static_cast<void *>(chunk), static_cast<int>(chunk->m_Count));
                maxSize = std::max(chunk->m_Count, maxSize);
        }
        debug_printf("max size = %d\n", static_cast<int>(maxSize));
}

bool CVertexBuffer::UseStreaming(const bool dynamic)
{
        return dynamic;
}

void CVertexBuffer::PrepareForRendering(VBChunk* chunk)
{
        chunk->m_Needed = true;
        m_HasNeededChunks = true;
}