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[1];
    OpenGL.GenTextures(1, id);
    OpenGL.BindTexture(target, id[0]);
    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(0, 0, bitmap.Width, bitmap.Height),
        ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
    OpenGL.TexImage2D(OpenGL.GL_TEXTURE_2D, 0, OpenGL.GL_RGBA, bitmap.Width, bitmap.Height, 0, OpenGL.GL_BGRA, OpenGL.GL_UNSIGNED_BYTE, bitmapData.Scan0);
    bitmap.UnlockBits(bitmapData);
    
    return id[0];
}

 

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 >= 0)
    {
        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(1, id);
    BindTextureTarget target = this.Target;
    OpenGL.BindTexture(target, id[0]);
    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, 0);
}

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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[1];
            OpenGL.GenSamplers(1, ids);
            this.Id = ids[0];
            //OpenGL.BindSampler(unit, ids[0]);
            OpenGL.BindSampler(unit, ids[0]);
            /* Clamping to edges is important to prevent artifacts when scaling */
            OpenGL.SamplerParameteri(ids[0], OpenGL.GL_TEXTURE_WRAP_R, (int)this.parameters.wrapR);
            OpenGL.SamplerParameteri(ids[0], OpenGL.GL_TEXTURE_WRAP_S, (int)this.parameters.wrapS);
            OpenGL.SamplerParameteri(ids[0], OpenGL.GL_TEXTURE_WRAP_T, (int)this.parameters.wrapT);
            /* Linear filtering usually looks best for text */
            OpenGL.SamplerParameteri(ids[0], OpenGL.GL_TEXTURE_MIN_FILTER, (int)this.parameters.minFilter);
            OpenGL.SamplerParameteri(ids[0], OpenGL.GL_TEXTURE_MAG_FILTER, (int)this.parameters.magFilter);
            // TODO: mipmap not used yet.

            OpenGL.BindSampler(unit, 0);
        }
        /// <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);
        }
    }

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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.

        }
    }

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">0</param>
        /// <param name="internalformat">OpenGL.GL_RGBA etc.</param>
        /// <param name="border">0</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(0, 0, bitmap.Width, bitmap.Height),
                ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
            if (target == BindTextureTarget.Texture1D)
            {
                OpenGL.TexImage1D((uint)target, 0, this.internalformat, bitmap.Width, 0, this.format, this.type, bitmapData.Scan0);
            }
            else if (target == BindTextureTarget.Texture2D)
            {
                OpenGL.TexImage2D((uint)target, 0, this.internalformat, bitmap.Width, bitmap.Height, 0, this.format, this.type, bitmapData.Scan0);
            }
            else
            { throw new NotImplementedException(); }

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

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;
            }
        }
    }

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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, 0, OpenGL.GL_RGBA32F, 0, 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[1];
    glGenFramebuffers(1, 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, 0);
    
    // create a depth buffer.
    var renderbufferId = new uint[1];
    glGenRenderbuffers(1, renderbufferId);
    glBindRenderbuffer(OpenGL.GL_RENDERBUFFER, renderbufferId[0]);
    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, 0);
    
    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, 0);

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[1];
        /// <summary>
        /// Framebuffer Id.
        /// </summary>
        public uint Id { get { return renderbuffer[0]; } }

        /// <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(1, renderbuffer);
            glBindRenderbuffer(OpenGL.GL_RENDERBUFFER, renderbuffer[0]);
            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(1, frameBuffer); 命令。

    /// <summary>
    /// Create, update, use and delete a framebuffer object.
    /// </summary>
    public partial class Framebuffer : IDisposable
    {
        uint[] frameBuffer = new uint[1];
        /// <summary>
        /// Framebuffer Id.
        /// </summary>
        public uint Id { get { return frameBuffer[0]; } }

        /// <summary>
        /// Create an empty framebuffer object.
        /// </summary>
        public Framebuffer()
        {
            glGenFramebuffers(1, 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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