I wrote a pretty long question here: c++ - setting up opengl view and projection transformations - Stack Overflow

but I’ll also add some of the questions details down below.

I am making some basic steps towards rendering with opengl. I wrote some shaders as well as a some math functions to do the linear algebra.

I can get a quad that’s 2d tris to render on screen but when it comes to applying any sort of transformations I see nothing.

Here is the relevant code as to the matrix data that I am sending to the gpu, etc.

**setup matricies**

```
mat4identity(&vm);
vec3f eye = {0, 0, 0};
vec3f center = {0, 0, -1};
vec3f up = {0, 1, 0};
mat4LookAt(&vm, &eye, ¢er, &up);
mat4print("lookat",&vm);
mat4OrthoProjection(&opm, 200, 0, 200, 0, 0.001, 1000.0);
mat4print("2d projection",&opm);
```

**render code**

```
glUseProgram(sp);
glBindVertexArray(vao1);
pMat = getUniformLocation(sp, "proj");
vMat = getUniformLocation(sp, "view");
transMat = getUniformLocation(sp, "transform");
glUniformMatrix4dv(pMat, 1, GL_FALSE, opm.m);
glUniformMatrix4dv(vMat, 1, GL_FALSE, vm.m);
glUniformMatrix4dv(transMat, 1, GL_FALSE, tm.m);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
glBindVertexArray(0);
```

the mat4 is a column major struct in c.

**mat4 lookat function**

```
mat4* lookat(vec3f* eye, vec3f* center, vec3f* up) {
vec3f x = {1, 0, 0};
vec3f y = {0, 1, 0};
vec3f z = {0, 0, 1};
z = vec3fsub(eye, center);
vec3fnorm(z);
x = vec3fcross(y, z);
y = vec3fcross(z, x);
vec3fnorm(x);
vec3fnorm(y);
double x1, y1, z1;
x1 = vec3fdotr(&x, eye);
y1 = vec3fdotr(&y, eye);
z1 = vec3fdotr(&z, eye);
double data[] = { (&x)->p[0], (&y)->p[0], (&z)->p[0], 0,
(&x)->p[1], (&y)->p[1], (&z)->p[1], 0,
(&x)->p[2], (&y)->p[2], (&z)->p[2], 0,
x1, y1, z1, 1 };
return makeMat4(data);
}
```

**orthographic projection code**

```
mat4* mat4Projection(double r, double l, double t, double b, double n, double f)
{
double data[] = { (2*n)/(r-l), 0, (r+l)/(r-l), 0,
0, (2*n)/(t-b), (t+b)/(t-b), 0,
0, 0, (-(f+n))/(f-n), (-2*(f*n))/(f-n),
0, 0, -1, 1 };
return makeMat4(data);
}
```

I also try to send down just a simple transform matrix that moves the objects 20 units in the +z direction. Running the above code and printing out the matrices along the way I get these results.

```
lookat matrix
[ 1.000000 0.000000 0.000000 0.000000 ]
[ 0.000000 1.000000 0.000000 0.000000 ]
[ 0.000000 0.000000 1.000000 0.000000 ]
[ 0.000000 0.000000 0.000000 1.000000 ]
2d projection matrix
[ 0.010000 0.000000 0.000000 -1.000000 ]
[ 0.000000 0.010000 0.000000 -1.000000 ]
[ 0.000000 0.000000 -0.002000 -1.000002 ]
[ 0.000000 0.000000 0.000000 1.000000 ]
translation matrix
[ 1.000000 0.000000 0.000000 0.000000 ]
[ 0.000000 1.000000 0.000000 0.000000 ]
[ 0.000000 0.000000 1.000000 20.000000 ]
[ 0.000000 0.000000 0.000000 1.000000 ]
```

The error could be at this line when I am sending the data to the gpu

```
glUniformMatrix4dv(pMat, 1, GL_FALSE, opm.m);
```

but again I am not sure. This is the vertex shader:

```
#version 330 core
uniform mat4 view;
uniform mat4 proj;
in vec3 position;
void main()
{
gl_Position = proj * view * vec4(position.x, position.y, position.z, 1.0);
}
```

removing the proj and view transformations I get the rectangle in the middle of the screen. Using either projection or view transformations and I can’t see anything on screen, just the clear background.