Custom matrices & OpenGL shaders. - c++

Question

I am trying to make a simple 4x4 matrix class.
The data (float) is a single dimension array, and I use this code to store numbers as if it were a grid.
const inline int ind1(short x, short y) { // Convert coords to spot on linear array, uses SIZE
return x * (SIZE >> 2) + y;
}
This part is in the .h file
float *data;
These are in the .cpp
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;
}
The problem is that when I try to multiply the matrix to my position in the vertex shader, the triangle or whatever I am drawing disappears.
My class has orthographic, perspective, translation, rotation, and scaling.
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;
}
Vertex code
#version 330
layout(location = 0) in vec3 pos;
uniform mat4 view_mat;
void main() {
gl_Position = view_mat * vec4(pos, 1.0);
}
Finally, here is how I send the data to the shader.
// 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);
Final note: My shaders do compile perfectly. When I run it without anything to do with matrices it works perfectly. (Dealing with color or modifying position).
Thanks

Answer 1

There are 2 issues in your code:
You use the wrong glUniform* function to set the view_mat uniform in your function Shader::GL_SET_UNIFORM_MATRIX. While glUniformMatrix4fv commits 16 floats for a 4*4* matrix, glUniformMatrix4x2fv commits 8 floats for a 4*2 matrix. See glUniform.
Further See 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
But your matrix is set up in row-major order:
const inline int ind1(short x, short y) {
return x * (SIZE >> 2) + y;
}
Either the ind1 function has to be changed to fix this issue:
const inline int ind1(short x, short y) {
return y * (SIZE >> 2) + x;
}
Or the matrix has to be transposed, when it is set to the uniform variable:
glUniformMatrix4fv(
location,
1,
GL_TRUE, // <----------------- transpose
matrix.getRawDataAsArray());
Or the vector has to be multiplied to the matrix from the left:
gl_Position = vec4(pos, 1.0) * view_mat;