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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。
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 }
CreateTexture
使用Texture
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 }
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。
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 }
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Sampler
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 }
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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 }
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。
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 }
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。
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 }
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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。
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 }
BitmapFiller
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 }
TexStorageImageFiller
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创建Texture
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 }
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：
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());
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。
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。
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 }
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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。
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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时间： 2024-10-03 21:50:04