矩阵的设置，例如着色器 [英] Setup of matrix for instance shader

问题描述

我想提请实例化的立方体

我可以叫 GL.DrawArraysInstanced（PrimitiveType.Triangles，0，36，2）; 成功。

我的问题是，所有的多维数据集在相同的位置，相同的旋转绘制。我怎样才能改变这种单独为每立方？

要创建不同的位置等等，我需要一个矩阵每个立方体，对不对？我创造了这个：

  Matrix4 [] =矩阵新Matrix4 [] {
 Matrix4.Identity，//什么也不做
 Matrix4.Identity * Matrix4.CreateTranslation（1,0,0）//移动一点点
}; 
 
 GL.BindBuffer（BufferTarget.ArrayBuffer，matrixBuffer）; 
 GL.BufferData（BufferTarget.ArrayBuffer，（IntPtr的）（的sizeof（浮动）* 16 * Matrices.Length），矩阵，BufferUsageHint.StaticDraw）; 
  

这应该创建一个缓冲区，我可以存储我的矩阵。 matrixBuffer 是指向我的缓冲区。 。林不知道如果尺寸是正确的，我把浮动* 4（为的Vector4）* 4（4矢量）*数组大小

绘制环路：

  GL.BindBuffer（BufferTarget.ArrayBuffer，matrixBuffer）; 
 GL.VertexAttribPointer（3，4，VertexAttribPointerType.Float，假，0，0）; 
 //GL.VertexAttribDivisor(3，）？; 
 GL.EnableVertexAttribArray（3）; 
 
 GL.DrawArraysInstanced（PrimitiveType.Triangles，0，36，2）; 
  

在 4比任何较大的数字VertexAttribPointer（...，4，VertexattribPointerType .Float，...）; 导致系统崩溃。我因子评分我有这个值设置为16？

林不知道如果我需要一个VertexAttribDivisor，可能是我这需要每36顶点，所以我称之为 GL.VertexAttribDivisor（3，36）; ？但是当我这样做，我看不出有任何的立方体

我的顶点着色器：

的#Version 330核心
布局（位置= 0）;在vec4颜色
布局（位置= 1）;在VEC2 texCoord
布局（位置= 2）;在mat4 instanceMatrix
布局（位置= 3）;

均匀mat4 projMatrix;

OUT vec4 vColor;
OUT VEC2 texCoords [];

无效的主要（）{
GL_POSITION = instanceMatrix * projMatrix * vec4（位置，1.0）;
// GL_POSITION = projMatrix * vec4（位置，1.0）;
texCoords [0] = texCoord;
vColor =颜色;
}


所以我的问题：

• 什么是错我的代码？


• 为什么可以VertexAttribPointer的大小参数设置为仅4？


• 什么是VertexAttribDivisor正确的值

---

编辑：

根据安灯科尔曼先生的答案我做了这个变化：

  GL.BindBuffer（BufferTarget.UniformBuffer，matrixBuffer）; 
 GL.BufferData（BufferTarget.UniformBuffer，（IntPtr的）（的sizeof（浮动）* 16），IntPtr.Zero，BufferUsageHint.DynamicDraw）; 
 //绑定缓冲到结合点
 GL.BindBufferBase（BufferRangeTarget.UniformBuffer，matrixUniform，matrixBuffer）; 
 
 matrixUniform = GL.GetUniformBlockIndex（shaderPrograminstanceMatrix）; 
 //绑定统一模块来结合点
 GL.UniformBlockBinding（shaderProgram，matrixUniform，0）; 
 
 GL.BufferSubData（BufferTarget.UniformBuffer，IntPtr.Zero，（IntPtr的）（的sizeof（浮动）* 16 * Matrices.Length），矩阵）; 
  

和着色器：

 的#Version 330芯vec4位置
布局（位置= 0）; //得到VEC3，填写W和在vec4色1.0 
布局（位置= 1）;在VEC2 texCoord 
布局（位置= 2）; 
 
均匀mat4 projMatrix; 
均匀UniformBlock 
 {mat4 instanceMatrix []; }; 
 
 OUT vec4 vColor; 
 OUT VEC2 texCoords []; 
 
无效的主要（）{
 GL_POSITION = projMatrix * instanceMatrix [0] *位置; 
 texCoords [0] = texCoord; 
 vColor =颜色; 
} 
  

解决方案

您已经发现了艰辛的道路顶点属性的位置始终四部分。

做一个4x4矩阵每个顶点属性的唯一方法是，如果你承认， mat4 为4x为 vec4 一样大。

考虑你的<$ C的声明$ C> mat4 顶点属性：

 在mat4 instanceMatrix布局（位置= 3）; 
  

您可能自然而然地想到那个位置的 3 存储16个浮点值，但你就错了。在GLSL的位置始终四部分。因此， mat4 instanceMatrix 竟占据4个不同的位置。

这实质上是如何 instanceMatrix 实际工作：

 布局（位置= 3）vec4 instanceMatrix_Column0;在vec4 instanceMatrix_Column1 
布局（位置= 4）;在vec4 instanceMatrix_Column2 
布局（位置= 5）;在vec4 instanceMatrix_Column3 
布局（位置= 6）; 
  

幸运的是，你不必写你的着色器的方式，这是非常有效的有 mat4 顶点属性。

不过，您的不的有写C＃代码的行为是那样：

  GL.BindBuffer（BufferTarget.ArrayBuffer，matrixBuffer）; 
 GL.VertexAttribPointer（3，4，VertexAttribPointerType.Float，假，64，0）; // C0 
 GL.VertexAttribPointer（4,4，VertexAttribPointerType.Float，假，64，16）; // C1 
 GL.VertexAttribPointer（5,4，VertexAttribPointerType.Float，假，64，32）; // C2 
 GL.VertexAttribPointer（6,4，VertexAttribPointerType.Float，假，64，48）; // C3 
  

同样的，你必须设置你的顶点属性除数为所有4个地点：

  GL.VertexAttribDivisor（3,1）; 
 GL.VertexAttribDivisor（4，1）; 
 GL.VertexAttribDivisor（5，1）; 
 GL.VertexAttribDivisor（6，1）; 
  

---

顺便说一下，因为顶点属性始终是4组分，实际上你可以声明：

 在vec4位置布局（位置= 0）; 
  

别再写这样丑陋的代码：

  GL_POSITION = instanceMatrix * projMatrix * vec4（位置，1.0）; 
  

这是因为在一个顶点属性缺少的组件会自动的OpenGL扩展。

&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP; （0.0，0.0，0.0，1.0）

如果您声明>的GLSL着色器XYZ顶点属性作为 vec4 是W 自动分配的 1.0

---

值实际上，你不想来存储您的矩阵每个顶点。即多个顶点属性的地点的浪费。你可能考虑的是制服，或更好的数组没有一个统一的缓冲区。您可以使用索引顶点着色器预先定义的变量数组： gl_InstanceID 。这确实是解决这个最明智的办法，因为你可以使用每个实例的详细性能比你有顶点属性的位置（发现自己的的最小值的在GL 3.3 16，只有少数的GPU真正支持多考虑到16）。

请有到顶点着色器可以使用 vec4 制服的数量限制在一个单一的调用，并在 mat4 算作4X的 vec4 的大小。使用统一的缓冲区将可以绘制更多的情况下，比普通的旧数组将制服。

I want to draw instanced cubes.

I can call GL.DrawArraysInstanced(PrimitiveType.Triangles, 0, 36, 2); successfully.

My problem is that all the cubes are drawn at the same position and same rotation. How can i change that individually for every cube?

To create different positions and so on, i need a matrix for each cube, right? I created this:

Matrix4[] Matrices = new Matrix4[]{
  Matrix4.Identity, //do nothing
  Matrix4.Identity * Matrix4.CreateTranslation(1,0,0) //move a little bit
};

GL.BindBuffer(BufferTarget.ArrayBuffer, matrixBuffer);
GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(sizeof(float) * 16 * Matrices.Length), Matrices, BufferUsageHint.StaticDraw);

This should create a buffer where i can store my matrices. matrixBuffer is the pointer to my buffer. Im not sure if the size is correct, i took float * 4 (for Vector4) * 4 (for 4 vectors) * array-size.

Draw Loop:

GL.BindBuffer(BufferTarget.ArrayBuffer, matrixBuffer);
GL.VertexAttribPointer(3, 4, VertexAttribPointerType.Float, false, 0, 0);
//GL.VertexAttribDivisor(3, ?);
GL.EnableVertexAttribArray(3);

GL.DrawArraysInstanced(PrimitiveType.Triangles, 0, 36, 2);

Any higher number than 4 in VertexAttribPointer(..., 4, VertexattribPointerType.Float, ...); causes a crash. I tought i have to set that value to 16?

Im not sure if i need a VertexAttribDivisor, probably i need this every 36th vertex so i call GL.VertexAttribDivisor(3, 36);? But when i do that, i can't see any cube.

My vertex shader:

#version 330 core
layout(location = 0) in vec3 position;
layout(location = 1) in vec4 color;
layout(location = 2) in vec2 texCoord;
layout(location = 3) in mat4 instanceMatrix;

uniform mat4 projMatrix;

out vec4 vColor;
out vec2 texCoords[];

void main(){
  gl_Position = instanceMatrix * projMatrix * vec4(position, 1.0);
  //gl_Position = projMatrix * vec4(position, 1.0);
  texCoords[0] = texCoord;
  vColor = color;
}

So my questions:

• What is wrong with my code?
• Why can i set the size-parameter of VertexAttribPointer only to 4?
• What is the correct value for VertexAttribDivisor?

---

Edit:

Based on the answer of Andon M. Coleman i made this changes:

GL.BindBuffer(BufferTarget.UniformBuffer, matrixBuffer);
GL.BufferData(BufferTarget.UniformBuffer, (IntPtr)(sizeof(float) * 16), IntPtr.Zero, BufferUsageHint.DynamicDraw);
//Bind Buffer to Binding Point
GL.BindBufferBase(BufferRangeTarget.UniformBuffer, matrixUniform, matrixBuffer);

matrixUniform = GL.GetUniformBlockIndex(shaderProgram, "instanceMatrix");
//Bind Uniform Block to Binding Point
GL.UniformBlockBinding(shaderProgram, matrixUniform, 0);

GL.BufferSubData(BufferTarget.UniformBuffer, IntPtr.Zero, (IntPtr)(sizeof(float) * 16 * Matrices.Length), Matrices);

And shader:

#version 330 core
layout(location = 0) in vec4 position; //gets vec3, fills w with 1.0
layout(location = 1) in vec4 color;
layout(location = 2) in vec2 texCoord;

uniform mat4 projMatrix;
uniform UniformBlock
{ mat4 instanceMatrix[]; };

out vec4 vColor;
out vec2 texCoords[];

void main(){
  gl_Position = projMatrix * instanceMatrix[0] * position;
  texCoords[0] = texCoord;
  vColor = color;
}

解决方案

You have discovered the hard way that vertex attribute locations are always 4-component.

The only way to make a 4x4 matrix a per-vertex attribute is if you concede that mat4 is 4x as large as vec4.

Consider the declaration of your mat4 vertex attribute:

layout(location = 3) in mat4 instanceMatrix;

You might naturally think that location 3 stores 16 floating-point values, but you would be wrong. Locations in GLSL are always 4-component. Thus, mat4 instanceMatrix actually occupies 4 different locations.

This is essentially how instanceMatrix actually works:

layout(location = 3) in vec4 instanceMatrix_Column0;
layout(location = 4) in vec4 instanceMatrix_Column1;
layout(location = 5) in vec4 instanceMatrix_Column2;
layout(location = 6) in vec4 instanceMatrix_Column3;

Fortunately, you do not have to write your shader that way, it is perfectly valid to have a mat4 vertex attribute.

However, you do have to write your C# code to behave that way:

GL.BindBuffer(BufferTarget.ArrayBuffer, matrixBuffer);
GL.VertexAttribPointer(3, 4, VertexAttribPointerType.Float, false, 64,  0); // c0
GL.VertexAttribPointer(4, 4, VertexAttribPointerType.Float, false, 64, 16); // c1
GL.VertexAttribPointer(5, 4, VertexAttribPointerType.Float, false, 64, 32); // c2
GL.VertexAttribPointer(6, 4, VertexAttribPointerType.Float, false, 64, 48); // c3

Likewise, you must setup your vertex attribute divisor for all 4 locations:

GL.VertexAttribDivisor (3, 1);
GL.VertexAttribDivisor (4, 1);
GL.VertexAttribDivisor (5, 1);
GL.VertexAttribDivisor (6, 1);

---

Incidentally, because vertex attributes are always 4-component, you can actually declare:

layout(location = 0) in vec4 position;

And stop writing ugly code like this:

gl_Position = instanceMatrix * projMatrix * vec4(position, 1.0);

This is because missing components in a vertex attribute are automatically expanded by OpenGL.

      (0.0, 0.0, 0.0, 1.0)

If you declare a vertex attribute as vec4 in the GLSL shader, but only supply data for XYZ, then W is automatically assigned a value of 1.0.

---

In actuality, you do not want to store your matrices per-vertex. That is a waste of multiple vertex attribute locations. What you may consider is an array of uniforms, or better yet a uniform buffer. You can index this array using the Vertex Shader pre-declared variable: gl_InstanceID. That is really the most sensible way to approach this, because you may find yourself using more properties per-instance than you have vertex attribute locations (mininum 16 in GL 3.3, only a few GPUs actually support more than 16).

Keep in mind that there is a limit to the number of vec4 uniforms a vertex shader can use in a single invocation, and that a mat4 counts as 4x the size of a vec4. Using a uniform buffer will allow you to draw many more instances than a plain old array of uniforms would.

这篇关于矩阵的设置，例如着色器的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！