CSharpGL(29)初步封装Texture和Framebuffer

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CSharpGL(29)初步封装Texture和Framebuffer

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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。

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下载

CSharpGL已在GitHub开源，欢迎对OpenGL有兴趣的同学加入（https://github.com/bitzhuwei/CSharpGL）

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封装Texture

过程式的Texture

首先观察一下平时是如何创建和使用Texture对象的。

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创建Texture

以创建2D Texture为例。

 uint CreateTexture(Bitmap bitmap)
 {
     glActiveTexture(OpenGL.GL_TEXTURE0);
     var id = new uint[];
     OpenGL.GenTextures(, id);
     OpenGL.BindTexture(target, id[]);
     OpenGL.TexParameteri(OpenGL.GL_TEXTURE_2D, OpenGL.GL_TEXTURE_WRAP_R, (int)OpenGL.GL_CLAMP_TO_EDGE);
     OpenGL.TexParameteri(OpenGL.GL_TEXTURE_2D, OpenGL.GL_TEXTURE_WRAP_S, (int)OpenGL.GL_CLAMP_TO_EDGE);
     OpenGL.TexParameteri(OpenGL.GL_TEXTURE_2D, OpenGL.GL_TEXTURE_WRAP_T, (int)OpenGL.GL_CLAMP_TO_EDGE);
     OpenGL.TexParameteri(OpenGL.GL_TEXTURE_2D, OpenGL.GL_TEXTURE_MIN_FILTER, (int)OpenGL.GL_REPEAT);
     OpenGL.TexParameteri(OpenGL.GL_TEXTURE_2D, OpenGL.GL_TEXTURE_MAG_FILTER, (int)OpenGL.GL_REPEAT);

     BitmapData bitmapData = bitmap.LockBits(new Rectangle(, , bitmap.Width, bitmap.Height),
         ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
     OpenGL.TexImage2D(OpenGL.GL_TEXTURE_2D, , OpenGL.GL_RGBA, bitmap.Width, bitmap.Height, , OpenGL.GL_BGRA, OpenGL.GL_UNSIGNED_BYTE, bitmapData.Scan0);
     bitmap.UnlockBits(bitmapData);

     return id[];
 }

CreateTexture

使用Texture

使用上述Texture的方式：

 void UseTexture(string textureNameInShader, uint textureId)
 {
     uint target = OpenGL.GL_TEXTURE0;
     glActiveTexture(target);
     OpenGL.BindTexture(OpenGL.GL_TEXTURE_2D, textureId);
     SetUniform("textureNameInShader", target - OpenGL.GL_TEXTURE0);
 }

 int SetUniform(string uniformName, uint v0)
 {
     int location = GetUniformLocation(uniformName);
     if (location >= )
     {
         glUniform1ui(GetUniformLocation(uniformName), v0);
     }
     return location;
 }

封装的Texture

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。

 void Initialize()
 {
     glActiveTexture(this.ActiveTexture);
     OpenGL.GenTextures(, id);
     BindTextureTarget target = this.Target;
     OpenGL.BindTexture(target, id[]);
     this.Sampler.Bind(this.ActiveTexture - OpenGL.GL_TEXTURE0, target);
     this.ImageFiller.Fill(target);
     OpenGL.GenerateMipmap((MipmapTarget)((uint)target));// TODO: does this work?
     //this.SamplerBuilder.Unbind(OpenGL.GL_TEXTURE0 - OpenGL.GL_TEXTURE0, this.Target);
     OpenGL.BindTexture(this.Target, );
 }

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Sampler

Sampler中主要就是那几个滤波选项。

     /// <summary>
     /// texture's settings.
     /// </summary>
     public class SamplerParameters
     {
         public TextureWrapping wrapS = TextureWrapping.ClampToEdge;
         public TextureWrapping wrapT = TextureWrapping.ClampToEdge;
         public TextureWrapping wrapR = TextureWrapping.ClampToEdge;
         public TextureFilter minFilter = TextureFilter.Linear;
         public TextureFilter magFilter = TextureFilter.Linear;

         public SamplerParameters() { }
     }

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Sampler的唯一任务就是在创建Texture时指定某些滤波。

     /// <summary>
     /// texture's settings.
     /// </summary>
     public abstract class SamplerBase
     {
         protected MipmapFilter mipmapFilter;
         public SamplerParameters Parameters { get; protected set; }

         /// <summary>
         /// texture's settings.
         /// </summary>
         /// <param name="parameters"></param>
         /// <param name="mipmapFilter"></param>
         public SamplerBase(SamplerParameters parameters, MipmapFilter mipmapFilter)
         {
             if (parameters == null)
             {
                 this.Parameters = new SamplerParameters();
             }
             else
             {
                 this.Parameters = parameters;
             }

             this.mipmapFilter = mipmapFilter;
         }

         /// <summary>
         ///
         /// </summary>
         /// <param name="unit">OpenGL.GL_TEXTURE0 etc.</param>
         /// <param name="target"></param>
         public abstract void Bind(uint unit, BindTextureTarget target);

     }

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。

     /// <summary>
     /// texture's settings.
     /// </summary>
     public partial class Sampler : SamplerBase, IDisposable
     {
         /// <summary>
         /// sampler's Id.
         /// </summary>
         public uint Id { get; private set; }

         /// <summary>
         /// texture's settings.
         /// </summary>
         /// <param name="parameters"></param>
         /// <param name="mipmapFiltering"></param>
         public Sampler(
             SamplerParameters parameters = null,
             MipmapFilter mipmapFiltering = MipmapFilter.LinearMipmapLinear)
             : base(parameters, mipmapFiltering)
         {

         }

         private bool initialized = false;
         /// <summary>
         ///
         /// </summary>
         public void Initialize(uint unit, BindTextureTarget target)
         {
             if (!this.initialized)
             {
                 this.DoInitialize(unit, target);
                 this.initialized = true;
             }
         }

         private void DoInitialize(uint unit, BindTextureTarget target)
         {
             var ids = new uint[];
             OpenGL.GenSamplers(, ids);
             this.Id = ids[];
             //OpenGL.BindSampler(unit, ids[0]);
             OpenGL.BindSampler(unit, ids[]);
             /* Clamping to edges is important to prevent artifacts when scaling */
             OpenGL.SamplerParameteri(ids[], OpenGL.GL_TEXTURE_WRAP_R, (int)this.parameters.wrapR);
             OpenGL.SamplerParameteri(ids[], OpenGL.GL_TEXTURE_WRAP_S, (int)this.parameters.wrapS);
             OpenGL.SamplerParameteri(ids[], OpenGL.GL_TEXTURE_WRAP_T, (int)this.parameters.wrapT);
             /* Linear filtering usually looks best for text */
             OpenGL.SamplerParameteri(ids[], OpenGL.GL_TEXTURE_MIN_FILTER, (int)this.parameters.minFilter);
             OpenGL.SamplerParameteri(ids[], OpenGL.GL_TEXTURE_MAG_FILTER, (int)this.parameters.magFilter);
             // TODO: mipmap not used yet.

             OpenGL.BindSampler(unit, );
         }
         /// <summary>
         /// texture's settings.
         /// </summary>
         /// <param name="unit">OpenGL.GL_TEXTURE0 etc.</param>
         /// <param name="target"></param>
         public override void Bind(uint unit, BindTextureTarget target)
         {
             if (!this.initialized) { this.Initialize(unit, target); }

             OpenGL.BindSampler(unit, this.Id);
         }
     }

Sampler

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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。

     /// <summary>
     /// texture's settings.
     /// </summary>
     public class FakeSampler : SamplerBase
     {

         /// <summary>
         /// texture's settings.
         /// </summary>
         /// <param name="parameters"></param>
         /// <param name="mipmapFiltering"></param>
         public FakeSampler(SamplerParameters parameters, MipmapFilter mipmapFiltering)
             : base(parameters, mipmapFiltering)
         {
         }

         /// <summary>
         /// texture's settings.
         /// </summary>
         /// <param name="unit">OpenGL.GL_TEXTURE0 etc.</param>
         /// <param name="target"></param>
         public override void Bind(uint unit, BindTextureTarget target)
         {
             /* Clamping to edges is important to prevent artifacts when scaling */
             OpenGL.TexParameteri((uint)target, OpenGL.GL_TEXTURE_WRAP_R, (int)this.parameters.wrapR);
             OpenGL.TexParameteri((uint)target, OpenGL.GL_TEXTURE_WRAP_S, (int)this.parameters.wrapS);
             OpenGL.TexParameteri((uint)target, OpenGL.GL_TEXTURE_WRAP_T, (int)this.parameters.wrapT);
             /* Linear filtering usually looks best for text */
             OpenGL.TexParameteri((uint)target, OpenGL.GL_TEXTURE_MIN_FILTER, (int)this.parameters.minFilter);
             OpenGL.TexParameteri((uint)target, OpenGL.GL_TEXTURE_MAG_FILTER, (int)this.parameters.magFilter);
             // TODO: mipmap filter not working yet.

         }
     }

FakeSampler

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。

     /// <summary>
     /// do nothing about sampling in building texture.
     /// </summary>
     public class NullSampler : SamplerBase
     {
         /// <summary>
         /// do nothing about sampling in building texture.
         /// </summary>
         public NullSampler() : base(null, MipmapFilter.LinearMipmapLinear) { }

         /// <summary>
         /// do nothing.
         /// </summary>
         /// <param name="unit">OpenGL.GL_TEXTURE0 etc.</param>
         /// <param name="target"></param>
         public override void Bind(uint unit, BindTextureTarget target)
         {
             // nothing to do.
         }
     }

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ImageFiller

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。

     /// <summary>
     /// build texture's content.
     /// </summary>
     public abstract class ImageFiller
     {

         /// <summary>
         /// build texture's content.
         /// </summary>
         /// <param name="target"></param>
         public abstract void Fill(BindTextureTarget target);
     }

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。

     /// <summary>
     /// build texture's content with Bitmap.
     /// </summary>
     public class BitmapFiller : ImageFiller
     {
         private System.Drawing.Bitmap bitmap;
         private int level;
         private uint internalformat;
         private int border;
         private uint format;
         private uint type;

         /// <summary>
         /// build texture's content with Bitmap.
         /// </summary>
         /// <param name="bitmap"></param>
         /// <param name="level"></param>
         /// <param name="internalformat">OpenGL.GL_RGBA etc.</param>
         /// <param name="border"></param>
         /// <param name="format">OpenGL.GL_BGRA etc.</param>
         /// <param name="type">OpenGL.GL_UNSIGNED_BYTE etc.</param>
         public BitmapFiller(System.Drawing.Bitmap bitmap,
             int level, uint internalformat, int border, uint format, uint type)
         {
             this.bitmap = bitmap;
             this.level = level;
             this.internalformat = internalformat;
             this.border = border;
             this.format = format;
             this.type = type;
         }

         /// <summary>
         /// build texture's content with Bitmap.
         /// </summary>
         /// <param name="target"></param>
         public override void Fill(BindTextureTarget target)
         {
             // generate texture.
             //  Lock the image bits (so that we can pass them to OGL).
             BitmapData bitmapData = bitmap.LockBits(new Rectangle(, , bitmap.Width, bitmap.Height),
                 ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
             if (target == BindTextureTarget.Texture1D)
             {
                 OpenGL.TexImage1D((uint)target, , this.internalformat, bitmap.Width, , this.format, this.type, bitmapData.Scan0);
             }
             else if (target == BindTextureTarget.Texture2D)
             {
                 OpenGL.TexImage2D((uint)target, , this.internalformat, bitmap.Width, bitmap.Height, , this.format, this.type, bitmapData.Scan0);
             }
             else
             { throw new NotImplementedException(); }

             //  Unlock the image.
             bitmap.UnlockBits(bitmapData);
         }
     }

BitmapFiller

还有一个常见的填充方式 glTexStorage2D() ，可以用下面的TexStorageImageFiller实现。

     /// <summary>
     ///
     /// </summary>
     public class TexStorageImageFiller : ImageFiller
     {
         private int levels;
         private uint internalFormat;
         private int width;
         private int height;

         /// <summary>
         ///
         /// </summary>
         /// <param name="levels"></param>
         /// <param name="internalFormat"></param>
         /// <param name="width"></param>
         /// <param name="height"></param>
         public TexStorageImageFiller(int levels, uint internalFormat, int width, int height)
         {
             // TODO: Complete member initialization
             this.levels = levels;
             this.internalFormat = internalFormat;
             this.width = width;
             this.height = height;
         }

         /// <summary>
         ///
         /// </summary>
         /// <param name="target"></param>
         public override void Fill(BindTextureTarget target)
         {
             switch (target)
             {
                 case BindTextureTarget.Unknown:
                     break;
                 case BindTextureTarget.Texture1D:
                     break;
                 case BindTextureTarget.Texture2D:
                     OpenGL.TexStorage2D(TexStorage2DTarget.Texture2D, levels, internalFormat, width, height);
                     break;
                 case BindTextureTarget.Texture3D:
                     break;
                 case BindTextureTarget.TextureCubeMap:
                     break;
                 case BindTextureTarget.TextureBuffer:
                     break;
                 default:
                     break;
             }
         }
     }

TexStorageImageFiller

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创建Texture

用封装的类型创建Texture的方式如下：

 Texture Create(Bitmap bitmap)
 {
     var texture = new Texture(BindTextureTarget.Texture2D,
         new BitmapFiller(bitmap, , OpenGL.GL_RGBA32F, , OpenGL.GL_BGRA, OpenGL.GL_UNSIGNED_BYTE),
         new SamplerParameters(
             TextureWrapping.ClampToEdge,
             TextureWrapping.ClampToEdge,
             TextureWrapping.ClampToEdge,
             TextureFilter.Linear,
             TextureFilter.Linear));
     texture.Initialize();

     return texture;
 }

使用Texture

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：

         /// <summary>
         /// get <see cref="samplerValue"/> from this texture.
         /// </summary>
         /// <param name="texture"></param>
         /// <returns></returns>
         public static samplerValue ToSamplerValue(this Texture texture)
         {
             return new samplerValue(
                 texture.Target,
                 texture.Id,
                 texture.ActiveTexture);
         }

这就可以用到设置shader中需要的Texture上：

this.SetUniform("tex", texture.ToSamplerValue());

封装Framebuffer

过程式的Framebuffer

首先观察一下平时是如何创建和使用Framebuffer对象的。

创建Framebuffer

为关注重点，这里直接传入Texture的Id。

 uint Create(int width, int height, uint textureId)
 {
     // create framebuffer.
     var frameBufferId = new uint[];
     glGenFramebuffers(, frameBufferId);
     glBindFramebuffer(OpenGL.GL_FRAMEBUFFER, frameBufferId);

     // attach texture as a color buffer.
     glFramebufferTexture2D(OpenGL.GL_FRAMEBUFFER, OpenGL.GL_COLOR_ATTACHMENT0, OpenGL.GL_TEXTURE_2D, textureId, );

     // create a depth buffer.
     var renderbufferId = new uint[];
     glGenRenderbuffers(, renderbufferId);
     glBindRenderbuffer(OpenGL.GL_RENDERBUFFER, renderbufferId[]);
     glRenderbufferStorage(OpenGL.GL_RENDERBUFFER, OpenGL.GL_DEPTH_COMPONENT, width, height);

     // attach depth buffer.
     glFramebufferRenderbuffer(OpenGL.GL_RENDERBUFFER, OpenGL.GL_DEPTH_ATTACHMENT, OpenGL.GL_RENDERBUFFER, renderbufferId);

     glBindFramebuffer(OpenGL.GL_RENDERBUFFER, );

     return frameBufferId;
 }

使用Framebuffer

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, );

封装的Framebuffer

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。

Renderbuffer

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。

     /// <summary>
     /// Create, update, use and delete a renderbuffer object.
     /// </summary>
     public partial class Renderbuffer
     {
         uint[] renderbuffer = new uint[];
         /// <summary>
         /// Framebuffer Id.
         /// </summary>
         public uint Id { get { return renderbuffer[]; } }

         /// <summary>
         /// Create, update, use and delete a renderbuffer object.
         /// </summary>
         /// <param name="width"></param>
         /// <param name="height"></param>
         /// <param name="internalformat">GL_DEPTH_COMPONENT, GL_RGBA etc.</param>
         /// <param name="bufferType"></param>
         public Renderbuffer(int width, int height, uint internalformat, RenderbufferType bufferType)
         {
             this.Width = width;
             this.Height = height;
             this.BufferType = bufferType;

             glGenRenderbuffers(, renderbuffer);
             glBindRenderbuffer(OpenGL.GL_RENDERBUFFER, renderbuffer[]);
             glRenderbufferStorage(OpenGL.GL_RENDERBUFFER,
                 internalformat, width, height);
         }

         public int Width { get; set; }
         public int Height { get; set; }
         public RenderbufferType BufferType { get; private set; }
     }

     public enum RenderbufferType
     {
         DepthBuffer,
         ColorBuffer,
     }

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创建Framebuffer

创建Framebuffer也很简单，实际上只是调用了一个 glGenFramebuffers(, frameBuffer); 命令。

     /// <summary>
     /// Create, update, use and delete a framebuffer object.
     /// </summary>
     public partial class Framebuffer : IDisposable
     {
         uint[] frameBuffer = new uint[];
         /// <summary>
         /// Framebuffer Id.
         /// </summary>
         public uint Id { get { return frameBuffer[]; } }

         /// <summary>
         /// Create an empty framebuffer object.
         /// </summary>
         public Framebuffer()
         {
             glGenFramebuffers(, frameBuffer);
         }
     }

     /// <summary>
     ///
     /// </summary>
     public enum FramebufferTarget : uint
     {
         /// <summary>
         /// used to draw(write only) something.
         /// </summary>
         DrawFramebuffer = OpenGL.GL_DRAW_FRAMEBUFFER,
         /// <summary>
         /// used to read from(read only).
         /// </summary>
         ReadFramebuffer = OpenGL.GL_READ_FRAMEBUFFER,
         /// <summary>
         /// both read/write.
         /// </summary>
         Framebuffer = OpenGL.GL_FRAMEBUFFER,
     }

使用Framebuffer

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。

总结

基于目前我对Texture和Framebuffer的了解，现在只能封装到这个地步。

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