c++ - 自定义矩阵和 OpenGL 着色器。

Question

我正在尝试制作一个简单的 4x4 矩阵类。数据 (float) 是一维数组，我使用此代码来存储数字，就像它是一个网格一样。

const inline int ind1(short x, short y) {  // Convert coords to spot on linear array, uses SIZE
    return x * (SIZE >> 2) + y;
}

这部分在.h文件中

float *data;

这些在.cpp中

Mat::Mat() {
    define();
    diagDefine(1.0f);
}

void Mat::define() {
    data = new float[SIZE];
    for (int x = 0; x < SIZE >> 2; x++) {
        for (int y = 0; y < SIZE >> 2; y++) {
            data[ind1(x, y)] = 0;
        }
    }
}
void Mat::diagDefine(float nval) {
    data[ind1(0, 0)] = nval;
    data[ind1(1, 1)] = nval;
    data[ind1(2, 2)] = nval;
    data[ind1(3, 3)] = nval;
}

问题是，当我尝试将矩阵乘以我在顶点着色器中的位置时，三角形或我正在绘制的任何东西都消失了。

我的类(class)有正交、透视、平移、旋转和缩放。

Mat Mat::getOrthographic(float left, float right, float top, float bottom, float near, float far) {
    Mat newmat;
    newmat.data[ind1(0, 0)] = 2.0f / (right - left);
    newmat.data[ind1(1, 1)] = 2.0f / (top - bottom);
    newmat.data[ind1(2, 2)] = 2.0f / (near - far);
    newmat.data[ind1(0, 3)] = (left + right) / (left - right);
    newmat.data[ind1(1, 3)] = (bottom + top) / (bottom - top);
    newmat.data[ind1(2, 3)] = (far + near) / (far - near);
    return newmat;
}

Mat Mat::getPerspective(float fov, float aspectratio, float near, float far) {
    Mat newmat;
    newmat.data[ind1(0, 0)] = (1.0f / tan((0.5f * fov) * (3.141519 / 180.0f))) / aspectratio;
    newmat.data[ind1(1, 1)] = 1.0f / tan((0.5f * fov) * (3.141519 / 180.0f));
    newmat.data[ind1(2, 2)] = (near + far) / (near - far);
    newmat.data[ind1(3, 2)] = -1.0f;
    newmat.data[ind1(2, 3)] = (2.0f * near * far) / (near - far);
    return newmat;
}

Mat Mat::getTranslation(Vec3f &vec) {
    Mat newmat;
    newmat.data[ind1(0, 3)] = vec.x;
    newmat.data[ind1(1, 3)] = vec.y;
    newmat.data[ind1(2, 3)] = vec.z;
    return newmat;
}

Mat Mat::getRotation(double angle, Vec3f &vec) {
    Mat newmat;
    float s = sin(angle);
    float c = cos(angle);
    newmat.data[ind1(0, 0)] = vec.x * (1.0f - c) + c;
    newmat.data[ind1(1, 0)] = vec.y * vec.x * (1.0f - c) + vec.z * s;
    newmat.data[ind1(2, 0)] = vec.x * vec.z * (1.0f - c) - vec.y * s;
    newmat.data[ind1(0, 1)] = vec.x * vec.y * (1.0f - c) - vec.z * s;
    newmat.data[ind1(1, 1)] = vec.y * (1.0f - c) + c;
    newmat.data[ind1(2, 1)] = vec.y * vec.z * (1.0f - c) + vec.x * s;
    newmat.data[ind1(0, 2)] = vec.x * vec.z * (1.0f - c) + vec.y * s;
    newmat.data[ind1(1, 2)] = vec.y * vec.z * (1.0f - c) - vec.x * s;
    newmat.data[ind1(2, 2)] = vec.z * (1.0f - c) + c;
    return newmat;
}

Mat Mat::getScale(Vec3f &vec) {
    Mat newmat;
    newmat.data[ind1(0, 0)] = vec.x;
    newmat.data[ind1(1, 1)] = vec.y;
    newmat.data[ind1(2, 2)] = vec.z;
    return newmat;
}

顶点代码

#version 330                                            

layout(location = 0) in vec3 pos;                       
uniform mat4 view_mat;                                  

void main() {                                           

  gl_Position =  view_mat * vec4(pos, 1.0);             

}                                                       

最后，这是我将数据发送到着色器的方式。

// In the matrix file
float *getRawDataAsArray() { return data; }

// In the shader.h file
void Shader::GL_SET_UNIFORM_MATRIX(const char *name, Mat matrix) {
    GLint location = glGetUniformLocation(program, name);
    if(location != -1) {
        glUniformMatrix4x2fv(location, 1, GL_FALSE, matrix.getRawDataAsArray());
    }
}

// In the main.cpp (sh is shader object that contained the GET_UNIFORM_MATRIX
sh.GL_SET_UNIFORM_MATRIX("view_mat", sod2::Mat::getRotation(3.141519 / 2, 0, 0, 1));
    sh.GL_SET_UNIFORM_4f("color", 0.0, 1.0, 0.0, 1.0);

最后的说明:我的着色器确实可以完美编译。当我在与矩阵无关的情况下运行它时，它工作得很好。 (处理颜色或修改位置)。谢谢

Answer 1

您的代码中有 2 个问题:

您使用错误的 glUniform* 函数在函数 Shader::GL_SET_UNIFORM_MATRIX 中设置了 view_mat uniform。 glUniformMatrix4fv 为 4*4* 矩阵提交 16 个 float ，而 glUniformMatrix4x2fv 为 4*2 矩阵提交 8 个 float 。
参见 glUniform .

进一步参见The OpenGL Shading Language 4.6, 5.4.2 Vector and Matrix Constructors, page 101 :

To initialize a matrix by specifying vectors or scalars, the components are assigned to the matrix elements in column-major order.

mat4(float, float, float, float,  // first column
     float, float, float, float,  // second column
     float, float, float, float,  // third column
     float, float, float, float); // fourth column

但是您的矩阵是按行优先顺序设置的:

const inline int ind1(short x, short y) { 
    return x * (SIZE >> 2) + y;
}

必须更改 ind1 函数以解决此问题:

const inline int ind1(short x, short y) { 
    return y * (SIZE >> 2) + x;
}

或者矩阵必须转置，当它被设置为uniform变量时:

glUniformMatrix4fv(
    location,
    1,
    GL_TRUE, // <----------------- transpose
    matrix.getRawDataAsArray());

或者 vector 必须从左边乘以矩阵:

gl_Position =  vec4(pos, 1.0) * view_mat;