164 lines
5.7 KiB
C++
164 lines
5.7 KiB
C++
/* Copyright (C) 2015 Wildfire Games.
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* This file is part of 0 A.D.
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*
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* 0 A.D. is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* 0 A.D. is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with 0 A.D. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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* encapsulation of VBOs with batching and sharing
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*/
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#ifndef INCLUDED_VERTEXBUFFER
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#define INCLUDED_VERTEXBUFFER
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#include "lib/res/graphics/ogl_tex.h"
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#include <list>
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#include <vector>
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/**
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* CVertexBuffer: encapsulation of ARB_vertex_buffer_object, also supplying
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* some additional functionality for sharing buffers between multiple objects.
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*
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* The class can be used in two modes, depending on the usage parameter:
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*
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* GL_STATIC_DRAW: Call Allocate() with backingStore = NULL. Then call
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* UpdateChunkVertices() with any pointer - the data will be immediately copied
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* to the VBO. This should be used for vertex data that rarely changes.
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*
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* GL_DYNAMIC_DRAW, GL_STREAM_DRAW: Call Allocate() with backingStore pointing
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* at some memory that will remain valid for the lifetime of the CVertexBuffer.
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* This should be used for vertex data that may change every frame.
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* Rendering is expected to occur in two phases:
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* - "Prepare" phase:
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* If this chunk is going to be used for rendering during the next Bind phase,
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* you must call PrepareForRendering().
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* If the vertex data in backingStore has been modified since the last Bind phase,
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* you must call UpdateChunkVertices().
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* - "Bind" phase:
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* Bind() can be called (multiple times). The vertex data will be uploaded
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* to the GPU if necessary.
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* It is okay to have multiple prepare/bind cycles per frame (though slightly less
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* efficient), but they must occur sequentially.
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*/
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class CVertexBuffer
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{
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NONCOPYABLE(CVertexBuffer);
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public:
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/// VBChunk: describes a portion of this vertex buffer
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struct VBChunk
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{
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/// Owning (parent) vertex buffer
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CVertexBuffer* m_Owner;
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/// Start index of this chunk in owner
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size_t m_Index;
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/// Number of vertices used by chunk
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size_t m_Count;
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/// If UseStreaming() is true, points at the data for this chunk
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void* m_BackingStore;
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/// If true, the VBO is not consistent with the chunk's backing store
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/// (and will need to be re-uploaded before rendering with this chunk)
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bool m_Dirty;
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/// If true, we have been told this chunk is going to be used for
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/// rendering in the next bind phase and will need to be uploaded
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bool m_Needed;
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private:
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// Only CVertexBuffer can construct/delete these
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// (Other people should use g_VBMan.Allocate, g_VBMan.Release)
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friend class CVertexBuffer;
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VBChunk() {}
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~VBChunk() {}
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};
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public:
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// constructor, destructor
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CVertexBuffer(size_t vertexSize, GLenum usage, GLenum target);
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~CVertexBuffer();
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/// Bind to this buffer; return pointer to address required as parameter
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/// to glVertexPointer ( + etc) calls
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u8* Bind();
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/// Get the address that Bind() will return, without actually binding
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u8* GetBindAddress();
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/// Unbind any currently-bound buffer, so glVertexPointer etc calls will not attempt to use it
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static void Unbind();
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/// Make the vertex data available for the next call to Bind()
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void PrepareForRendering(VBChunk* chunk) { chunk->m_Needed = true; }
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/// Update vertex data for given chunk. Transfers the provided data to the actual OpenGL vertex buffer.
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void UpdateChunkVertices(VBChunk* chunk, void* data);
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size_t GetVertexSize() const { return m_VertexSize; }
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size_t GetBytesReserved() const;
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size_t GetBytesAllocated() const;
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/// Returns true if this vertex buffer is compatible with the specified vertex type and intended usage.
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bool CompatibleVertexType(size_t vertexSize, GLenum usage, GLenum target);
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void DumpStatus();
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/**
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* Given the usage flags of a buffer that has been (or will be) allocated:
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*
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* If true, we assume the buffer is going to be modified on every frame,
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* so we will re-upload the entire buffer every frame using glMapBuffer.
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* This requires the buffer's owner to hold onto its backing store.
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*
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* If false, we assume it will change rarely, and use glSubBufferData to
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* update it incrementally. The backing store can be freed to save memory.
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*/
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static bool UseStreaming(GLenum usage);
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protected:
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friend class CVertexBufferManager; // allow allocate only via CVertexBufferManager
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/// Try to allocate a buffer of given number of vertices (each of given size),
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/// and with the given type - return null if no free chunks available
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VBChunk* Allocate(size_t vertexSize, size_t numVertices, GLenum usage, GLenum target, void* backingStore);
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/// Return given chunk to this buffer
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void Release(VBChunk* chunk);
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private:
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/// Vertex size of this vertex buffer
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size_t m_VertexSize;
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/// Number of vertices of above size in this buffer
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size_t m_MaxVertices;
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/// List of free chunks in this buffer
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std::list<VBChunk*> m_FreeList;
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/// List of allocated chunks
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std::list<VBChunk*> m_AllocList;
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/// Available free vertices - total of all free vertices in the free list
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size_t m_FreeVertices;
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/// Handle to the actual GL vertex buffer object
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GLuint m_Handle;
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/// Raw system memory for systems not supporting VBOs
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u8* m_SysMem;
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/// Usage type of the buffer (GL_STATIC_DRAW etc)
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GLenum m_Usage;
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/// Buffer target (GL_ARRAY_BUFFER, GL_ELEMENT_ARRAY_BUFFER)
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GLenum m_Target;
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};
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#endif
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