Is glm::ortho() actually wrong?

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It doesn’t appear that it should be broken from the source code (v 0.9.3.4)

template <typename valType> 
GLM_FUNC_QUALIFIER detail::tmat4x4<valType> ortho
(
    valType const & left, 
    valType const & right, 
    valType const & bottom, 
    valType const & top, 
    valType const & zNear, 
    valType const & zFar
)
{
    detail::tmat4x4<valType> Result(1);
    Result[0][0] = valType(2) / (right - left);
    Result[1][1] = valType(2) / (top - bottom);
    Result[2][2] = - valType(2) / (zFar - zNear);
    Result[3][0] = - (right + left) / (right - left);
    Result[3][1] = - (top + bottom) / (top - bottom);
    Result[3][2] = - (zFar + zNear) / (zFar - zNear);
    return Result;
}

My only thought is that this template might be creating a matrix of integers (as you’ve passed all ints to the function), and thus doing integer division instead of floating point. Can you try appending .f to all your parameters?

glm::mat4 projMat = glm::ortho( 0.f, 400.f, 0.f, 400.f, -1.f, 1.f );

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