CODEWITHSUNDEEP
c3dmatrix
krb
krb

Reputation: 16345

Concat two 4x4 matrices together?

I have a matrix type that is defined as:

struct __transform_t
{
    float m11, m12, m13, m14;
    float m21, m22, m23, m24;
    float m31, m32, m33, m34;
    float m41, m42, m43, m44;
};

How would I concat one matrix to another? I want to "merge" the matrices to get a result that is a combination of both transformations. Basically, I'm trying to make a simple layering system, so if a parent layer is transformed, the child layer (that is visually inside the parent) should also inherit those transformations as well as have its own.

I'm trying to do it like in the example below, but I don't think that is the right way:

void transform_concat(transform_t* orig, transform_t* delta)
{
#define __act(x) orig->m##x += delta->m##x;

    __act(11); __act(12); __act(13); __act(14);
    __act(21); __act(22); __act(23); __act(24);
    __act(31); __act(32); __act(33); __act(34);
    __act(41); __act(42); __act(43); __act(44);

#undef __act
}

Upvotes: 1

Views: 918

Answers (1)

unwind
unwind

Reputation: 400029

This sounds like transformation matrix compositing, so look up matrix multiplication. Since you have explicit fields for each value in the matrix, it'll be hard to write looping implementations.

Upvotes: 2

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