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;
}
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;
}
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!