我正在将OpenGL 1.1应用程序移植到OpenGL ES 2.0，并且正在编写一个包装器来实现OpenGL 1.1功能。在我开始调用glPushMatrix()和glPopMatrix()之前，我的代码似乎工作正常。我认为我对这些应该如何实施的理解是不正确的。
在将它推回堆栈之前，我是否计算最终的旋转/平移/缩放？我应该只保留一个模型视图矩阵（而不是将其分成三个）吗？变换是否以正确的顺序应用？
这是我的转换矩阵的代码
static std::vector<GLfloat> vertices;
static std::vector<std::vector<GLfloat>> rotationMatrixStack;
static std::vector<std::vector<GLfloat>> scalingMatrixStack;
static std::vector<GLfloat> rotationMatrix =
{
1.0f, 0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f
};
static std::vector<GLfloat> scalingMatrix =
{
1.0f, 0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f
};
static std::vector<GLfloat> translationMatrix =
{
1.0f, 0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f
};
static std::vector<GLfloat> orthographicMatrix =
{
.0025f, 0.0f, 0.0f, -1.0f,
0.0f, .0025f, 0.0f, -1.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f
};
void glTranslatef (GLfloat x, GLfloat y, GLfloat z)
{
float translation[] =
{
1.0f, 0.0f, 0.0f, x,
0.0f, 1.0f, 0.0f, y,
0.0f, 0.0f, 1.0f, z,
0.0f, 0.0f, 0.0f, 1.0f
};
multiplyMatrix(translation , &translationMatrix[0], &translationMatrix[0]);
}
void glScalef (GLfloat x, GLfloat y, GLfloat z)
{
float scaling[] =
{
x, 0.0f, 0.0f, 0.0f,
0.0f, y, 0.0f, 0.0f,
0.0f, 0.0f, z, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f
};
multiplyMatrix(scaling , &scalingMatrix[0], &scalingMatrix[0]);
}
void glRotatef (GLfloat angle, GLfloat x, GLfloat y, GLfloat z)
{
glTranslatef(-x, -y, -z);
GLfloat radians = angle * M_PI/180;
float zRotation[] =
{
cos(radians), -sin(radians), 0.0f, 0.0f,
sin(radians), cos(radians), 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f
};
multiplyMatrix(zRotation , &rotationMatrix[0], &rotationMatrix[0]);
glTranslatef(x,y,z);
}
void glLoadIdentity (void)
{
rotationMatrix, scalingMatrix, translationMatrix =
{
1.0f, 0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f
};
}
void multiplyMatrix(float* a, float* b, float* product)
{
int a_heigth = 4;
int a_width = 4;
int b_heigth = 4;
int b_width = 4;
int product_heigth = a_heigth;
int product_width = b_width;
float intermediateMatrix[product_heigth * product_width] = {0};
for (int product_row = 0; product_row < product_heigth; product_row++)
{
for (int product_column = 0; product_column < product_width; product_column++)
{
float value = 0;
//std::cout << "r[" << (product_row*product_width) + product_column << "] = ";
for (int multiplication_index = 0; multiplication_index < a_width ; multiplication_index++)
{
value += a[(product_row * a_width) + multiplication_index] * b[product_column + (b_heigth * multiplication_index)];
//std::cout << "( a[" << (product_row * a_width) + multiplication_index << "] * b[" << product_column + (b_heigth * multiplication_index) << "] ) + ";
}
//std::cout << std::endl;
intermediateMatrix[(product_row*product_width) + product_column] = value;
}
}
for (int i = 0; i < product_heigth * product_width; i++)
{
product[i] = intermediateMatrix[i];
}
}
这是矩阵堆栈的代码
static std::vector<std::vector<GLfloat>> translationMatrixStack;
void glPushMatrix()
{
rotationMatrixStack.push_back(rotationMatrix);
scalingMatrixStack.push_back(scalingMatrix);
translationMatrixStack.push_back(translationMatrix);
}
void glPopMatrix()
{
rotationMatrix = rotationMatrixStack.back();
scalingMatrix = scalingMatrixStack.back();
translationMatrix = translationMatrixStack.back();
rotationMatrixStack.pop_back();
scalingMatrixStack.pop_back();
translationMatrix.pop_back();
}
这是顶点着色器代码
attribute highp vec4 myVertex;
uniform mediump mat4 orthographicMatrix;
uniform mediump mat4 translationMatrix;
uniform mediump mat4 scalingMatrix;
uniform mediump mat4 rotationMatrix;
void main(void)
{
gl_Position = orthographicMatrix * translationMatrix * scalingMatrix * rotationMatrix * ( myVertex) ;
}";
答案 0 :(得分：1)
您没有单独的矩阵堆栈用于旋转，平移和缩放。在OpenGL中，每种矩阵模式都有一个矩阵堆栈（参见glMatrixMode）。矩阵模式为GL_MODELVIEW，GL_PROJECTION和GL_TEXTURE。
请参阅glTranslate的文档：
glTranslate按x y z生成翻译。当前矩阵（参见glMatrixMode）乘以此平移矩阵，产品替换当前矩阵。
glRotate的文档：
glRotate围绕向量x y z产生角度旋转。当前矩阵（参见glMatrixMode）乘以旋转矩阵，产品替换当前矩阵。
以及glScale的文档：
glScale会在x，y和z轴上产生不均匀的缩放。这三个参数表示沿三个轴中的每个轴的所需比例因子。 当前矩阵（参见glMatrixMode）乘以该比例矩阵。
这意味着您需要一个矩阵堆栈，并且所有操作都在相同的矩阵堆栈上运行。
注意，矩阵乘法C = A * B的工作方式如下：
Matrix4x4 A, B, C;
// C = A * B
for ( int k = 0; k < 4; ++ k )
for ( int j = 0; j < 4; ++ j )
C[k][j] = A[0][l] * B[k][0] + A[1][j] * B[k][1] + A[2][j] * B[k][2] + A[3][j] * B[k][3];
4 * 4矩阵看起来像这样：
c0 c1 c2 c3 c0 c1 c2 c3
[ Xx Yx Zx Tx ] [ 0 4 8 12 ]
[ Xy Yy Zy Ty ] [ 1 5 9 13 ]
[ Xz Yz Zz Tz ] [ 2 6 10 14 ]
[ 0 0 0 1 ] [ 3 7 11 15 ]
4 * 4矩阵的记忆图像如下所示：
[ Xx, Xy, Xz, 0, Yx, Yy, Yz, 0, Zx, Zy, Zz, 0, Tx, Ty, Tz, 1 ]
这意味着您必须调整矩阵运算：
static std::vector<std::vector<GLfloat>> modelViewMatrixStack;
static std::vector<GLfloat> modelViewMatrix{
1.0f, 0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f };
void multiplyMatrix( float A[], float B[], float P[] )
{
float C[16];
for ( int k = 0; k < 4; ++ k ) {
for ( int l = 0; l < 4; ++ l ) {
C[k*4+j] =
A[0*4+j] * B[k*4+0] +
A[1*4+j] * B[k*4+1] +
A[2*4+j] * B[k*4+2] +
A[3*4+j] * B[k*4+3];
}
}
std::copy(C, C+16, P);
}
void glTranslatef( GLfloat x, GLfloat y, GLfloat z )
{
float translation[]{
1.0f, 0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
x, y, z, 1.0f };
multiplyMatrix(&modelViewMatrix[0], translation, &modelViewMatrix[0]);
}
void glScalef( GLfloat x, GLfloat y, GLfloat z )
{
float scaling[]{
x, 0.0f, 0.0f, 0.0f,
0.0f, y, 0.0f, 0.0f,
0.0f, 0.0f, z, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f };
multiplyMatrix(&modelViewMatrix[0], scaling, &modelViewMatrix[0]);
}
void glRotatef( GLfloat angle, GLfloat x, GLfloat y, GLfloat z )
{
float radians = angle * M_PI/180;
float c = cos(radians);
float s = sin(radians);
float rotation[16]{
x*x*(1.0f-c)+c, x*y*(1.0f-c)-z*s, x*z*(1.0f-c)+y*s, 0.0f,
y*x*(1.0f-c)+z*s, y*y*(1.0f-c)+c, y*z*(1.0f-c)-x*s, 0.0f,
z*x*(1.0f-c)-y*s z*y*(1.0f-c)+x*s, z*z*(1.0f-c)+c, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f };
multiplyMatrix(&rotationMatrix[0], rotation, &rotationMatrix[0]);
}
进一步了解：