Merge 'remotes/trunk'

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

/* Copyright (C) 2016 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/>.
 */

/*
 * encapsulation of VBOs with sharing
 */

#include "precompiled.h"
#include "ps/Errors.h"
#include "lib/ogl.h"
#include "lib/sysdep/cpu.h"
#include "Renderer.h"
#include "VertexBuffer.h"
#include "VertexBufferManager.h"
#include "ps/CLogger.h"

// 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
#define MAX_VB_SIZE_BYTES               (4*1024*1024)

CVertexBuffer::CVertexBuffer(size_t vertexSize, GLenum usage, GLenum target)
        : m_VertexSize(vertexSize), m_Handle(0), m_SysMem(0), m_Usage(usage), m_Target(target)
{
        size_t size = MAX_VB_SIZE_BYTES;

        if (target == GL_ARRAY_BUFFER) // vertex data buffer
        {
                // 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);
        }

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

        // allocate raw buffer
        if (g_Renderer.m_Caps.m_VBO)
        {
                pglGenBuffersARB(1, &m_Handle);
                pglBindBufferARB(m_Target, m_Handle);
                pglBufferDataARB(m_Target, m_MaxVertices * m_VertexSize, 0, m_Usage);
                pglBindBufferARB(m_Target, 0);
        }
        else
        {
                m_SysMem = new u8[m_MaxVertices * m_VertexSize];
        }

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

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

        if (m_Handle)
                pglDeleteBuffersARB(1, &m_Handle);

        delete[] m_SysMem;

        typedef std::list<VBChunk*>::iterator Iter;
        for (Iter iter = m_FreeList.begin(); iter != m_FreeList.end(); ++iter)
                delete *iter;
}


bool CVertexBuffer::CompatibleVertexType(size_t vertexSize, GLenum usage, GLenum target)
{
        if (usage != m_Usage || target != m_Target || vertexSize != m_VertexSize)
                return false;

        return true;
}

///////////////////////////////////////////////////////////////////////////////
// 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(size_t vertexSize, size_t numVertices, GLenum usage, GLenum target, void* backingStore)
{
        // check this is the right kind of buffer
        if (!CompatibleVertexType(vertexSize, usage, target))
                return 0;

        if (UseStreaming(usage))
                ENSURE(backingStore != NULL);

        // quick check there's enough vertices spare to allocate
        if (numVertices > m_FreeVertices)
                return 0;

        // trawl free list looking for first free chunk with enough space
        VBChunk* chunk = 0;
        typedef std::list<VBChunk*>::iterator Iter;
        for (Iter iter = m_FreeList.begin(); iter != m_FreeList.end(); ++iter) {
                if (numVertices <= (*iter)->m_Count) {
                        chunk = *iter;
                        // remove this chunk from the free list
                        m_FreeList.erase(iter);
                        m_FreeVertices -= chunk->m_Count;
                        // no need to search further ..
                        break;
                }
        }

        if (!chunk) {
                // no big enough spare chunk available
                return 0;
        }

        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 > numVertices)
        {
                VBChunk* newchunk = new VBChunk;
                newchunk->m_Owner = this;
                newchunk->m_Count = chunk->m_Count - numVertices;
                newchunk->m_Index = chunk->m_Index + numVertices;
                m_FreeList.push_front(newchunk);
                m_FreeVertices += newchunk->m_Count;

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

        // 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.remove(chunk);

        typedef std::list<VBChunk*>::iterator Iter;

        // 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, and repeat until no more are found
        bool coalesced;
        do
        {
                coalesced = false;
                for (Iter iter = m_FreeList.begin(); iter != m_FreeList.end(); ++iter)
                {
                        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;
                                m_FreeList.erase(iter);
                                coalesced = true;
                                break;
                        }
                }
        }
        while (coalesced);

        m_FreeList.push_front(chunk);
}

///////////////////////////////////////////////////////////////////////////////
// UpdateChunkVertices: update vertex data for given chunk
void CVertexBuffer::UpdateChunkVertices(VBChunk* chunk, void* data)
{
        if (g_Renderer.m_Caps.m_VBO)
        {
                ENSURE(m_Handle);
                if (UseStreaming(m_Usage))
                {
                        // The VBO 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
                {
                        pglBindBufferARB(m_Target, m_Handle);
                        pglBufferSubDataARB(m_Target, chunk->m_Index * m_VertexSize, chunk->m_Count * m_VertexSize, data);
                        pglBindBufferARB(m_Target, 0);
                }
        }
        else
        {
                ENSURE(m_SysMem);
                memcpy(m_SysMem + chunk->m_Index * m_VertexSize, data, chunk->m_Count * m_VertexSize);
        }
}

///////////////////////////////////////////////////////////////////////////////
// Bind: bind to this buffer; return pointer to address required as parameter
// to glVertexPointer ( + etc) calls
u8* CVertexBuffer::Bind()
{
        if (!g_Renderer.m_Caps.m_VBO)
                return m_SysMem;

        pglBindBufferARB(m_Target, m_Handle);

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

                if (needUpload)
                {
                        // Tell the driver that it can reallocate the whole VBO
                        pglBufferDataARB(m_Target, m_MaxVertices * m_VertexSize, NULL, m_Usage);

                        // (In theory, glMapBufferRange with GL_MAP_INVALIDATE_BUFFER_BIT could be used
                        // here instead of glBufferData(..., NULL, ...) plus glMapBuffer(), but with
                        // current Intel Windows GPU drivers (as of 2015-01) it's much faster if you do
                        // the explicit glBufferData.)

                        while (true)
                        {
                                void* p = pglMapBufferARB(m_Target, GL_WRITE_ONLY);
                                if (p == NULL)
                                {
                                        // This shouldn't happen unless we run out of virtual address space
                                        LOGERROR("glMapBuffer failed");
                                        break;
                                }

#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(p, 0, m_MaxVertices * m_VertexSize);
#endif

                                // Copy only the chunks we need. (This condition is helpful when
                                // the VBO 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)
                                                memcpy((u8 *)p + chunk->m_Index * m_VertexSize, chunk->m_BackingStore, chunk->m_Count * m_VertexSize);

                                if (pglUnmapBufferARB(m_Target) == GL_TRUE)
                                        break;

                                // Unmap might fail on e.g. resolution switches, so just try again
                                // and hope it will eventually succeed
                                debug_printf("glUnmapBuffer failed, trying again...\n");
                        }

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

                // Reset the flags for the next phase
                for (VBChunk* const& chunk : m_AllocList)
                        chunk->m_Needed = false;
        }

        return (u8*)0;
}

u8* CVertexBuffer::GetBindAddress()
{
        if (g_Renderer.m_Caps.m_VBO)
                return (u8*)0;
        else
                return m_SysMem;
}

void CVertexBuffer::Unbind()
{
        if (g_Renderer.m_Caps.m_VBO)
        {
                pglBindBufferARB(GL_ARRAY_BUFFER, 0);
                pglBindBufferARB(GL_ELEMENT_ARRAY_BUFFER, 0);
        }
}

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()
{
        debug_printf("freeverts = %d\n", (int)m_FreeVertices);

        size_t maxSize = 0;
        typedef std::list<VBChunk*>::iterator Iter;
        for (Iter iter = m_FreeList.begin(); iter != m_FreeList.end(); ++iter)
        {
                debug_printf("free chunk %p: size=%d\n", (void *)*iter, (int)((*iter)->m_Count));
                maxSize = std::max((*iter)->m_Count, maxSize);
        }
        debug_printf("max size = %d\n", (int)maxSize);
}

bool CVertexBuffer::UseStreaming(GLenum usage)
{
        return (usage == GL_DYNAMIC_DRAW || usage == GL_STREAM_DRAW);
}