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CSharpGL(29)初步封装Texture和Framebuffer
Texture和Framebuffer是OpenGL进行3D渲染高级效果必不可少的利器。有了Texture和Framebuffer就可以实现体渲染(Volume Rendering)等效果。现在到了对Texture和Framebuffer的创建、修改、使用进行封装的时候。
CSharpGL已在GitHub开源，欢迎对OpenGL有兴趣的同学加入（https://github.com/bitzhuwei/CSharpGL）
首先观察一下平时是如何创建和使用Texture对象的。
以创建2D Texture为例。
1 uint CreateTexture(Bitmap bitmap) 2 { 3 glActiveTexture(OpenGL.GL_TEXTURE0); 4 var id = new uint[1]; 5 OpenGL.GenTextures(1, id); 6 OpenGL.BindTexture(target, id[0]); 7 OpenGL.TexParameteri(OpenGL.GL_TEXTURE_2D, OpenGL.GL_TEXTURE_WRAP_R, (int)OpenGL.GL_CLAMP_TO_EDGE); 8 OpenGL.TexParameteri(OpenGL.GL_TEXTURE_2D, OpenGL.GL_TEXTURE_WRAP_S, (int)OpenGL.GL_CLAMP_TO_EDGE); 9 OpenGL.TexParameteri(OpenGL.GL_TEXTURE_2D, OpenGL.GL_TEXTURE_WRAP_T, (int)OpenGL.GL_CLAMP_TO_EDGE); 10 OpenGL.TexParameteri(OpenGL.GL_TEXTURE_2D, OpenGL.GL_TEXTURE_MIN_FILTER, (int)OpenGL.GL_REPEAT); 11 OpenGL.TexParameteri(OpenGL.GL_TEXTURE_2D, OpenGL.GL_TEXTURE_MAG_FILTER, (int)OpenGL.GL_REPEAT); 12 13 BitmapData bitmapData = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height), 14 ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb); 15 OpenGL.TexImage2D(OpenGL.GL_TEXTURE_2D, 0, OpenGL.GL_RGBA, bitmap.Width, bitmap.Height, 0, OpenGL.GL_BGRA, OpenGL.GL_UNSIGNED_BYTE, bitmapData.Scan0); 16 bitmap.UnlockBits(bitmapData); 17 18 return id[0]; 19 }
使用上述Texture的方式：
1 void UseTexture(string textureNameInShader, uint textureId) 2 { 3 uint target = OpenGL.GL_TEXTURE0; 4 glActiveTexture(target); 5 OpenGL.BindTexture(OpenGL.GL_TEXTURE_2D, textureId); 6 SetUniform("textureNameInShader", target - OpenGL.GL_TEXTURE0); 7 } 8 9 int SetUniform(string uniformName, uint v0) 10 { 11 int location = GetUniformLocation(uniformName); 12 if (location >= 0) 13 { 14 glUniform1ui(GetUniformLocation(uniformName), v0); 15 } 16 return location; 17 }
从上述创建Texture的过程可知，创建Texture主要有2个步骤：设置Sampler和填充Texture数据。Sampler就是各个滤波选项。填充数据就是用glTexImage2D()一类的命令指定Texture的内容。
1 void Initialize() 2 { 3 glActiveTexture(this.ActiveTexture); 4 OpenGL.GenTextures(1, id); 5 BindTextureTarget target = this.Target; 6 OpenGL.BindTexture(target, id[0]); 7 this.Sampler.Bind(this.ActiveTexture - OpenGL.GL_TEXTURE0, target); 8 this.ImageFiller.Fill(target); 9 OpenGL.GenerateMipmap((MipmapTarget)((uint)target));// TODO: does this work? 10 //this.SamplerBuilder.Unbind(OpenGL.GL_TEXTURE0 - OpenGL.GL_TEXTURE0, this.Target); 11 OpenGL.BindTexture(this.Target, 0); 12 }
Sampler中主要就是那几个滤波选项。
1 /// <summary> 2 /// texture‘s settings. 3 /// </summary> 4 public class SamplerParameters 5 { 6 public TextureWrapping wrapS = TextureWrapping.ClampToEdge; 7 public TextureWrapping wrapT = TextureWrapping.ClampToEdge; 8 public TextureWrapping wrapR = TextureWrapping.ClampToEdge; 9 public TextureFilter minFilter = TextureFilter.Linear; 10 public TextureFilter magFilter = TextureFilter.Linear; 11 12 public SamplerParameters() { } 13 }
Sampler的唯一任务就是在创建Texture时指定某些滤波。
1 /// <summary> 2 /// texture‘s settings. 3 /// </summary> 4 public abstract class SamplerBase 5 { 6 protected MipmapFilter mipmapFilter; 7 public SamplerParameters Parameters { get; protected set; } 8 9 /// <summary> 10 /// texture‘s settings. 11 /// </summary> 12 /// <param name="parameters"></param> 13 /// <param name="mipmapFilter"></param> 14 public SamplerBase(SamplerParameters parameters, MipmapFilter mipmapFilter) 15 { 16 if (parameters == null) 17 { 18 this.Parameters = new SamplerParameters(); 19 } 20 else 21 { 22 this.Parameters = parameters; 23 } 24 25 this.mipmapFilter = mipmapFilter; 26 } 27 28 /// <summary> 29 /// 30 /// </summary> 31 /// <param name="unit">OpenGL.GL_TEXTURE0 etc.</param> 32 /// <param name="target"></param> 33 public abstract void Bind(uint unit, BindTextureTarget target); 34 35 }
实际上为了简化指定Sampler的操作，OpenGL提供了一个Sampler对象。这里顺便也把它封装了。
1 /// <summary> 2 /// texture‘s settings. 3 /// </summary> 4 public partial class Sampler : SamplerBase, IDisposable 5 { 6 /// <summary> 7 /// sampler‘s Id. 8 /// </summary> 9 public uint Id { get; private set; } 10 11 /// <summary> 12 /// texture‘s settings. 13 /// </summary> 14 /// <param name="parameters"></param> 15 /// <param name="mipmapFiltering"></param> 16 public Sampler( 17 SamplerParameters parameters = null, 18 MipmapFilter mipmapFiltering = MipmapFilter.LinearMipmapLinear) 19 : base(parameters, mipmapFiltering) 20 { 21 22 } 23 24 private bool initialized = false; 25 /// <summary> 26 /// 27 /// </summary> 28 public void Initialize(uint unit, BindTextureTarget target) 29 { 30 if (!this.initialized) 31 { 32 this.DoInitialize(unit, target); 33 this.initialized = true; 34 } 35 } 36 37 private void DoInitialize(uint unit, BindTextureTarget target) 38 { 39 var ids = new uint[1]; 40 OpenGL.GenSamplers(1, ids); 41 this.Id = ids[0]; 42 //OpenGL.BindSampler(unit, ids[0]); 43 OpenGL.BindSampler(unit, ids[0]); 44 /* Clamping to edges is important to prevent artifacts when scaling */ 45 OpenGL.SamplerParameteri(ids[0], OpenGL.GL_TEXTURE_WRAP_R, (int)this.parameters.wrapR); 46 OpenGL.SamplerParameteri(ids[0], OpenGL.GL_TEXTURE_WRAP_S, (int)this.parameters.wrapS); 47 OpenGL.SamplerParameteri(ids[0], OpenGL.GL_TEXTURE_WRAP_T, (int)this.parameters.wrapT); 48 /* Linear filtering usually looks best for text */ 49 OpenGL.SamplerParameteri(ids[0], OpenGL.GL_TEXTURE_MIN_FILTER, (int)this.parameters.minFilter); 50 OpenGL.SamplerParameteri(ids[0], OpenGL.GL_TEXTURE_MAG_FILTER, (int)this.parameters.magFilter); 51 // TODO: mipmap not used yet. 52 53 OpenGL.BindSampler(unit, 0); 54 } 55 /// <summary> 56 /// texture‘s settings. 57 /// </summary> 58 /// <param name="unit">OpenGL.GL_TEXTURE0 etc.</param> 59 /// <param name="target"></param> 60 public override void Bind(uint unit, BindTextureTarget target) 61 { 62 if (!this.initialized) { this.Initialize(unit, target); } 63 64 OpenGL.BindSampler(unit, this.Id); 65 } 66 }
当然也可以不用这个OpenGL的Sampler对象，直接用glTexParameteri()等指令。这就像是一个假的Sampler对象在工作。
1 /// <summary> 2 /// texture‘s settings. 3 /// </summary> 4 public class FakeSampler : SamplerBase 5 { 6 7 /// <summary> 8 /// texture‘s settings. 9 /// </summary> 10 /// <param name="parameters"></param> 11 /// <param name="mipmapFiltering"></param> 12 public FakeSampler(SamplerParameters parameters, MipmapFilter mipmapFiltering) 13 : base(parameters, mipmapFiltering) 14 { 15 } 16 17 /// <summary> 18 /// texture‘s settings. 19 /// </summary> 20 /// <param name="unit">OpenGL.GL_TEXTURE0 etc.</param> 21 /// <param name="target"></param> 22 public override void Bind(uint unit, BindTextureTarget target) 23 { 24 /* Clamping to edges is important to prevent artifacts when scaling */ 25 OpenGL.TexParameteri((uint)target, OpenGL.GL_TEXTURE_WRAP_R, (int)this.parameters.wrapR); 26 OpenGL.TexParameteri((uint)target, OpenGL.GL_TEXTURE_WRAP_S, (int)this.parameters.wrapS); 27 OpenGL.TexParameteri((uint)target, OpenGL.GL_TEXTURE_WRAP_T, (int)this.parameters.wrapT); 28 /* Linear filtering usually looks best for text */ 29 OpenGL.TexParameteri((uint)target, OpenGL.GL_TEXTURE_MIN_FILTER, (int)this.parameters.minFilter); 30 OpenGL.TexParameteri((uint)target, OpenGL.GL_TEXTURE_MAG_FILTER, (int)this.parameters.magFilter); 31 // TODO: mipmap filter not working yet. 32 33 } 34 }
当然，有的时候根本不需要指定任何滤波选项。这可以用一个空的Sampler类型实现。
1 /// <summary> 2 /// do nothing about sampling in building texture. 3 /// </summary> 4 public class NullSampler : SamplerBase 5 { 6 /// <summary> 7 /// do nothing about sampling in building texture. 8 /// </summary> 9 public NullSampler() : base(null, MipmapFilter.LinearMipmapLinear) { } 10 11 /// <summary> 12 /// do nothing. 13 /// </summary> 14 /// <param name="unit">OpenGL.GL_TEXTURE0 etc.</param> 15 /// <param name="target"></param> 16 public override void Bind(uint unit, BindTextureTarget target) 17 { 18 // nothing to do. 19 } 20 }
填充数据就是用 glTexImage2D() 、 glTexStorage2D() 等指令设置Texture的内容。ImageFiller就是封装这一操作的。
1 /// <summary> 2 /// build texture‘s content. 3 /// </summary> 4 public abstract class ImageFiller 5 { 6 7 /// <summary> 8 /// build texture‘s content. 9 /// </summary> 10 /// <param name="target"></param> 11 public abstract void Fill(BindTextureTarget target); 12 }
对于常见的以 System.Drawing.Bitmap 为数据源填充Texture的情形，可以用下面的BitmapFiller。它可以作为1D/2D的Texture对象的填充器。
1 /// <summary> 2 /// build texture‘s content with Bitmap. 3 /// </summary> 4 public class BitmapFiller : ImageFiller 5 { 6 private System.Drawing.Bitmap bitmap; 7 private int level; 8 private uint internalformat; 9 private int border; 10 private uint format; 11 private uint type; 12 13 /// <summary> 14 /// build texture‘s content with Bitmap. 15 /// </summary> 16 /// <param name="bitmap"></param> 17 /// <param name="level">0</param> 18 /// <param name="internalformat">OpenGL.GL_RGBA etc.</param> 19 /// <param name="border">0</param> 20 /// <param name="format">OpenGL.GL_BGRA etc.</param> 21 /// <param name="type">OpenGL.GL_UNSIGNED_BYTE etc.</param> 22 public BitmapFiller(System.Drawing.Bitmap bitmap, 23 int level, uint internalformat, int border, uint format, uint type) 24 { 25 this.bitmap = bitmap; 26 this.level = level; 27 this.internalformat = internalformat; 28 this.border = border; 29 this.format = format; 30 this.type = type; 31 } 32 33 /// <summary> 34 /// build texture‘s content with Bitmap. 35 /// </summary> 36 /// <param name="target"></param> 37 public override void Fill(BindTextureTarget target) 38 { 39 // generate texture. 40 // Lock the image bits (so that we can pass them to OGL). 41 BitmapData bitmapData = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height), 42 ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb); 43 if (target == BindTextureTarget.Texture1D) 44 { 45 OpenGL.TexImage1D((uint)target, 0, this.internalformat, bitmap.Width, 0, this.format, this.type, bitmapData.Scan0); 46 } 47 else if (target == BindTextureTarget.Texture2D) 48 { 49 OpenGL.TexImage2D((uint)target, 0, this.internalformat, bitmap.Width, bitmap.Height, 0, this.format, this.type, bitmapData.Scan0); 50 } 51 else 52 { throw new NotImplementedException(); } 53 54 // Unlock the image. 55 bitmap.UnlockBits(bitmapData); 56 } 57 }
还有一个常见的填充方式 glTexStorage2D() ，可以用下面的TexStorageImageFiller实现。
1 /// <summary> 2 /// 3 /// </summary> 4 public class TexStorageImageFiller : ImageFiller 5 { 6 private int levels; 7 private uint internalFormat; 8 private int width; 9 private int height; 10 11 /// <summary> 12 /// 13 /// </summary> 14 /// <param name="levels"></param> 15 /// <param name="internalFormat"></param> 16 /// <param name="width"></param> 17 /// <param name="height"></param> 18 public TexStorageImageFiller(int levels, uint internalFormat, int width, int height) 19 { 20 // TODO: Complete member initialization 21 this.levels = levels; 22 this.internalFormat = internalFormat; 23 this.width = width; 24 this.height = height; 25 } 26 27 /// <summary> 28 /// 29 /// </summary> 30 /// <param name="target"></param> 31 public override void Fill(BindTextureTarget target) 32 { 33 switch (target) 34 { 35 case BindTextureTarget.Unknown: 36 break; 37 case BindTextureTarget.Texture1D: 38 break; 39 case BindTextureTarget.Texture2D: 40 OpenGL.TexStorage2D(TexStorage2DTarget.Texture2D, levels, internalFormat, width, height); 41 break; 42 case BindTextureTarget.Texture3D: 43 break; 44 case BindTextureTarget.TextureCubeMap: 45 break; 46 case BindTextureTarget.TextureBuffer: 47 break; 48 default: 49 break; 50 } 51 } 52 }
用封装的类型创建Texture的方式如下：
1 Texture Create(Bitmap bitmap) 2 { 3 var texture = new Texture(BindTextureTarget.Texture2D, 4 new BitmapFiller(bitmap, 0, OpenGL.GL_RGBA32F, 0, OpenGL.GL_BGRA, OpenGL.GL_UNSIGNED_BYTE), 5 new SamplerParameters( 6 TextureWrapping.ClampToEdge, 7 TextureWrapping.ClampToEdge, 8 TextureWrapping.ClampToEdge, 9 TextureFilter.Linear, 10 TextureFilter.Linear)); 11 texture.Initialize(); 12 13 return texture; 14 }
Texutre.Id就是用 glGenTextures() 获得的id。Texture中记录了此Texture的ActiveTexture、Target等属性。配合CSharpGL中的 samplerValue ，我们有：
1 /// <summary> 2 /// get <see cref="samplerValue"/> from this texture. 3 /// </summary> 4 /// <param name="texture"></param> 5 /// <returns></returns> 6 public static samplerValue ToSamplerValue(this Texture texture) 7 { 8 return new samplerValue( 9 texture.Target, 10 texture.Id, 11 texture.ActiveTexture); 12 }
这就可以用到设置shader中需要的Texture上：
this.SetUniform("tex", texture.ToSamplerValue());
首先观察一下平时是如何创建和使用Framebuffer对象的。
为关注重点，这里直接传入Texture的Id。
1 uint Create(int width, int height, uint textureId) 2 { 3 // create framebuffer. 4 var frameBufferId = new uint[1]; 5 glGenFramebuffers(1, frameBufferId); 6 glBindFramebuffer(OpenGL.GL_FRAMEBUFFER, frameBufferId); 7 8 // attach texture as a color buffer. 9 glFramebufferTexture2D(OpenGL.GL_FRAMEBUFFER, OpenGL.GL_COLOR_ATTACHMENT0, OpenGL.GL_TEXTURE_2D, textureId, 0); 10 11 // create a depth buffer. 12 var renderbufferId = new uint[1]; 13 glGenRenderbuffers(1, renderbufferId); 14 glBindRenderbuffer(OpenGL.GL_RENDERBUFFER, renderbufferId[0]); 15 glRenderbufferStorage(OpenGL.GL_RENDERBUFFER, OpenGL.GL_DEPTH_COMPONENT, width, height); 16 17 // attach depth buffer. 18 glFramebufferRenderbuffer(OpenGL.GL_RENDERBUFFER, OpenGL.GL_DEPTH_ATTACHMENT, OpenGL.GL_RENDERBUFFER, renderbufferId); 19 20 glBindFramebuffer(OpenGL.GL_RENDERBUFFER, 0); 21 22 return frameBufferId; 23 }
使用方式与Texture类似，只要绑定就可以了。
glBindFramebuffer(OpenGL.GL_FRAMEBUFFER, frameBufferId);
用完再解绑。
glBindFramebuffer(OpenGL.GL_FRAMEBUFFER, 0);
Framebuffer就是一个盒子，单独创建一个Framebuffer基本上是没什么用的。必须Attach一些colorbuffer/depthbuffer/texture才能发挥作用。
一个Framebuffer能够绑定多个texture和colorbuffer，只能绑定一个depthbuffer。
colorbuffer和depthbuffer都属于Renderbuffer的一种，其创建方式相同，只不过有一个标识其为colorbuffer还是depthbuffer的标志不同。
创建Renderbuffer很简单。
1 /// <summary> 2 /// Create, update, use and delete a renderbuffer object. 3 /// </summary> 4 public partial class Renderbuffer 5 { 6 uint[] renderbuffer = new uint[1]; 7 /// <summary> 8 /// Framebuffer Id. 9 /// </summary> 10 public uint Id { get { return renderbuffer[0]; } } 11 12 /// <summary> 13 /// Create, update, use and delete a renderbuffer object. 14 /// </summary> 15 /// <param name="width"></param> 16 /// <param name="height"></param> 17 /// <param name="internalformat">GL_DEPTH_COMPONENT, GL_RGBA etc.</param> 18 /// <param name="bufferType"></param> 19 public Renderbuffer(int width, int height, uint internalformat, RenderbufferType bufferType) 20 { 21 this.Width = width; 22 this.Height = height; 23 this.BufferType = bufferType; 24 25 glGenRenderbuffers(1, renderbuffer); 26 glBindRenderbuffer(OpenGL.GL_RENDERBUFFER, renderbuffer[0]); 27 glRenderbufferStorage(OpenGL.GL_RENDERBUFFER, 28 internalformat, width, height); 29 } 30 31 public int Width { get; set; } 32 public int Height { get; set; } 33 public RenderbufferType BufferType { get; private set; } 34 } 35 36 public enum RenderbufferType 37 { 38 DepthBuffer, 39 ColorBuffer, 40 }
创建Framebuffer也很简单，实际上只是调用了一个 glGenFramebuffers(1, frameBuffer); 命令。
1 /// <summary> 2 /// Create, update, use and delete a framebuffer object. 3 /// </summary> 4 public partial class Framebuffer : IDisposable 5 { 6 uint[] frameBuffer = new uint[1]; 7 /// <summary> 8 /// Framebuffer Id. 9 /// </summary> 10 public uint Id { get { return frameBuffer[0]; } } 11 12 /// <summary> 13 /// Create an empty framebuffer object. 14 /// </summary> 15 public Framebuffer() 16 { 17 glGenFramebuffers(1, frameBuffer); 18 } 19 } 20 21 /// <summary> 22 /// 23 /// </summary> 24 public enum FramebufferTarget : uint 25 { 26 /// <summary> 27 /// used to draw(write only) something. 28 /// </summary> 29 DrawFramebuffer = OpenGL.GL_DRAW_FRAMEBUFFER, 30 /// <summary> 31 /// used to read from(read only). 32 /// </summary> 33 ReadFramebuffer = OpenGL.GL_READ_FRAMEBUFFER, 34 /// <summary> 35 /// both read/write. 36 /// </summary> 37 Framebuffer = OpenGL.GL_FRAMEBUFFER, 38 }
使用方式与Texture类似，只要绑定就可以了。
framebuffer.Bind();// glBindFramebuffer(OpenGL.GL_FRAMEBUFFER, framebufferId);
用完再解绑。
framebuffer.Unbind();// glBindFramebuffer(OpenGL.GL_FRAMEBUFFER, 0);
这与未封装的使用方式没什么区别。
基于目前我对Texture和Framebuffer的了解，现在只能封装到这个地步。
CSharpGL(29)初步封装Texture和Framebuffer
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原文地址：http://www.cnblogs.com/bitzhuwei/p/CSharpGL-29-wrapping-Texture-and-Framebuffer.html
