为什么我的转换矩阵需要转置？ [英] Why does my translation matrix needs to be transposed?

问题描述

我正在使用OpenGL的小型图形引擎，我有一些问题与我的翻译矩阵。我使用OpenGL 3.3，GLSL和C ++。
情况是这样的：我定义了一个小的立方体，我想在屏幕上呈现。立方体使用它自己的坐标系，所以我创建了一个模型矩阵，以便能够转换立方体。为了使自己更容易一点，我开始只使用一个翻译矩阵作为多维数据集的模型矩阵，经过一些编码我已经设法使一切工作，立方体出现在屏幕上。没有什么都特别，但有一件事我的翻译矩阵，我觉得有点奇怪。

现在据我所知，一个翻译矩阵定义如下：

  1,0,0，x 
 0，1，0，y 
 0，0 ，1，z 
 0，0，0，1 
  

为了我。当我以这种方式定义我的翻译矩阵时，屏幕上没有任何东西出现。它只有在我这样定义我的翻译矩阵时才有效：

  1，0，0，0 
 0，1 ，0，0 
 0，0，1，0 
x，y，z，1 
  

$ b b

现在我已经在我的代码几次，以找出为什么是这种情况，但我似乎不知道为什么，或者我只是错误，做一个翻译矩阵需要定义像转置一个在这上面？

我的矩阵被定义为从左到右，从上到下的一维数组。

这是我的一些代码可能有帮助：

  //这是在多维数据集渲染之前调用
 void DisplayObject :: updateMatrices（）
 {
 modelMatrix = identityMatrix（）; 
 modelMatrix = modelMatrix * translateMatrix（xPos，yPos，zPos）; 
 
 / * update modelview-projection matrix * / 
 mvpMatrix = modelMatrix *（* projMatrix）; 
} 
 
 //这将创建我的转换矩阵，使多维数据集消失
 const Matrix4 translateMatrix（float x，float y，float z）
 {
 Matrix4 tranMatrix = identityMatrix（）; 
 
 tranMatrix.data [3] = x; 
 tranMatrix.data [7] = y; 
 tranMatrix.data [11] = z; 
 
 return Matrix4（tranMatrix）; 
} 
  

这是我简单的测试顶点着色器：

  #version 150核心
 
在vec3 vPos中; 
 
 uniform mat4 mvpMatrix; 
 
 void main（）
 {
 gl_Position = mvpMatrix * vec4（vPos，1.0）; 
} 
  

我也做过测试检查我的矩阵乘法是否有效。
I * randomMatrix仍然只是randomMatrix

我希望你们可以帮助。
感谢

编辑：

这是我将矩阵数据发送到OpenGL的方法：

  void DisplayObject :: render（）
 {
 updateMatrices 
 
 glBindVertexArray（vaoID）; 
 glUseProgram（progID）; 
 glUniformMatrix4fv（glGetUniformLocation（progID，mvpMatrix），1，GL_FALSE，& mvpMatrix.data [0]）; 
 glDrawElements（GL_TRIANGLES，bufferSize [index]，GL_UNSIGNED_INT，0）; 
} 
  

mvpMatrix.data是std :: vector：

解决方案

对于OpenGL

  1,0,0 ，0 
 0，1，0，0 
 0，0，1，0 
x，y，z，1 
  

是正确的转换矩阵。
为什么？ Opengl使用列主题矩阵排序。这是您最初呈现的矩阵的移调，它在 row-major 顺序中。

请参阅：http://www.mindcontrol.org/~hplus/graphics/matrix-layout.html

I'm working on a small graphics engine using OpenGL and I'm having some issues with my translation matrix. I'm using OpenGL 3.3, GLSL and C++. The situation is this: I have defined a small cube which I want to render on screen. The cube uses it's own coordinate system, so I created a model matrix to be able to transform the cube. To make it myself a bit easier I started out with just a translation matrix as the cube's model matrix and after a bit of coding I've managed to make everything work and the cube appears on the screen. Nothing all to special, but there is one thing about my translation matrix that I find a bit odd.

Now as far as I know, a translation matrix is defined as follows:

1, 0, 0, x
0, 1, 0, y
0, 0, 1, z
0, 0, 0, 1

However, this does not work for me. When I define my translation matrix this way, nothing appears on the screen. It only works when I define my translation matrix like this:

1, 0, 0, 0
0, 1, 0, 0
0, 0, 1, 0
x, y, z, 1

Now I've been over my code several times to find out why this is the case, but I can't seem to find out why or am I just wrong and does a translation matrix needs to be defined like the transposed one here above?

My matrices are defined as a one-dimensional array going from left to right, top to bottom.

Here is some of my code that might help:

//this is called just before cube is being rendered
void DisplayObject::updateMatrices()
{
    modelMatrix = identityMatrix();
    modelMatrix = modelMatrix * translateMatrix( xPos, yPos, zPos );

    /* update modelview-projection matrix */
    mvpMatrix = modelMatrix * (*projMatrix);
}

//this creates my translation matrix which causes the cube to disappear
const Matrix4 translateMatrix( float x, float y, float z )
{
    Matrix4 tranMatrix = identityMatrix();

    tranMatrix.data[3]  = x;
    tranMatrix.data[7]  = y;
    tranMatrix.data[11] = z;

    return Matrix4(tranMatrix);
}

This is my simple test vertex shader:

#version 150 core

in vec3 vPos;

uniform mat4 mvpMatrix;

void main()
{
    gl_Position = mvpMatrix * vec4(vPos, 1.0);
}

I've also did tests to check if my matrix multiplication works and it does. I * randomMatrix is still just randomMatrix

I hope you guys can help. Thanks

EDIT:

This is how I send the matrix data to OpenGL:

void DisplayObject::render()
{
    updateMatrices();

    glBindVertexArray(vaoID);
    glUseProgram(progID);
    glUniformMatrix4fv( glGetUniformLocation(progID, "mvpMatrix"), 1, GL_FALSE, &mvpMatrix.data[0] );
    glDrawElements(GL_TRIANGLES, bufferSize[index], GL_UNSIGNED_INT, 0);
}

mvpMatrix.data is a std::vector:

解决方案

For OpenGL

1, 0, 0, 0
0, 1, 0, 0
0, 0, 1, 0
x, y, z, 1

Is the correct Translation Matrix. Why? Opengl Uses column-major matrix ordering. Which is the Transpose of the Matrix you initially presented, which is in row-major ordering. Row major is used in most math text-books and also DirectX, so it is a common point of confusion for those new to OpenGL.

See: http://www.mindcontrol.org/~hplus/graphics/matrix-layout.html

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