cglm/README.md

# 🎥 OpenGL Mathematics (glm) for `C`
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The original glm library is for C++ only (templates, namespaces, classes...), this library targeted to C99 but currently you can use it for C89 safely by language extensions e.g `__restrict`

#### Documentation

Almost all functions (inline versions) and parameters are documented inside related headers. <br />
Complete documentation is in progress: http://cglm.readthedocs.io

#### Note for previous versions:

- _dup (duplicate) is changed to _copy. For instance `glm_vec_dup -> glm_vec_copy`
- OpenGL related functions are dropped to make this lib platform/third-party independent
- make sure you have latest version and feel free to report bugs, troubles

#### Note for C++ developers:
If you don't aware about original GLM library yet, you may also want to look at:
https://github.com/g-truc/glm

#### Note for new comers (Important):
- `vec4` and `mat4` variables must be aligned. (There will be unaligned versions later)
- **in** and **[in, out]** parameters must be initialized (please). But **[out]** parameters not, initializing out param is  also redundant
- All functions are inline if you don't want to use pre-compiled versions with glmc_ prefix, you can ignore build process. Just incliude headers.
- if your debugger takes you to cglm headers then make sure you are not trying to copy vec4 to vec3 or alig issues...
- Welcome!

#### Note for experienced developers:
- Since I'm testing this library in my projects, sometimes bugs occurs; finding that bug[s] and making improvements would be more easy with multiple developer/contributor and their projects or knowledge. Consider to make some tests if you suspect something is wrong and any feedbacks, contributions and bug reports are always welcome. 

#### Allocations? 
`cglm` doesn't alloc any memory on heap. So it doesn't provide any allocator. You should alloc memory for **out** parameters too if you pass pointer of memory location. Don't forget that **vec4** (also quat/**versor**) and **mat4** must be aligned (16-bytes), because *cglm* uses SIMD instructions to optimize most operations if available. 

#### Returning vector or matrix... ?
Since almost all types are arrays and **C** doesn't allow returning arrays, so **cglm** doesn't support this feature. In the future *cglm* may use **struct** for some types for this purpose. 

#### Other APIs like Vulkan, Metal, Dx? 
Currently *cglm* uses default clip space configuration (-1, 1) for camera functions (perspective, extract corners...), in the future other clip space configurations will be supported

<hr/>

<table>
  <tbody>
    <tr>
      <td>
        <div>Like some other graphics libraries (especially OpenGL) this library use Column-Major layout to keep matrices in the memory. </div>
        <div>&nbsp;</div>
        <div>In the future the library may support an option to use row-major layout, CURRENTLY if you need to row-major layout you will need to transpose it. </div>
      </td>
      <td>
        <img src="https://upload.wikimedia.org/wikipedia/commons/3/3f/Matrix_Columns.svg" width="300px" />
      </td>
    </tr>
  </tbody>
</table>

## Features
- general purpose matrix operations (mat4, mat3)
- chain matrix multiplication (square only)
- general purpose vector operations (cross, dot, rotate, proj, angle...)
- affine transforms
- matrix decomposition (extract rotation, scaling factor)
- optimized affine transform matrices (mul, rigid-body inverse)
- camera (lookat)
- projections (ortho, perspective)
- quaternions
- euler angles / yaw-pitch-roll to matrix
- extract euler angles
- inline or pre-compiled function call
- frustum (extract view frustum planes, corners...)
- bounding box  (AABB in Frustum (culling), crop, merge...)

<hr />

You have two option to call a function/operation: inline or library call (link)
Almost all functions are marked inline (always_inline) so compiler probably will inline.
To call pre-compiled version, just use `glmc_` (c stands for 'call') instead of `glm_`.

```C
  #include <cglm/cglm.h>   /* for inline */
  #include <cglm/call.h>   /* for library call (this also includes cglm.h) */

  mat4 rot, trans, rt;
  /* ... */
  glm_mul(trans, rot, rt);  /* inline */
  glmc_mul(trans, rot, rt); /* call from library */
```
Most of math functions are optimized manualy with SSE2 if available, if not? Dont worry there are non-sse versions of all operations

You can pass matrices and vectors as array to functions rather than get address.

```C
  mat4 m = {
    1, 0, 0, 0,
    0, 1, 0, 0,
    0, 0, 1, 0,
    0, 0, 0, 1
  };

  glm_translate(m, (vec3){1.0f, 0.0f, 0.0f});
```

Library contains general purpose mat4 mul and inverse functions but also contains some special form (optimized) of these functions for affine transform matrices. If you want to multiply two affine transform matrices you can use glm_mul instead of glm_mat4_mul and glm_inv_tr (ROT + TR) instead glm_mat4_inv
```C
/* multiplication */
mat4 modelMat;
glm_mul(T, R, modelMat);

/* othonormal rot + tr matrix inverse (rigid-body) */
glm_inv_tr(modelMat);
```

## License
MIT. check the LICENSE file

## Build

### Unix (Autotools)

```text
$ sh ./build-deps.sh # run only once (dependencies)
$
$ sh autogen.sh
$ ./configure
$ make
$ make install
$ [sudo] make install
```

### Windows (MSBuild)
Windows related build files, project files are located in `win` folder,
make sure you are inside `cglm/win` folder.
Code Analysis are enabled, it may take awhile to build

```Powershell
$ cd win
$ .\build.bat
```
if `msbuild` won't work (because of multi version VS) then try to build with `devenv`:
```Powershell
$ devenv cglm.sln /Build Release
```

## How to use
If you want to use inline versions of funcstions then; include main header
```C
#include <cglm/cglm.h>
```
the haeder will include all headers. Then call func you want e.g. rotate vector by axis:
```C
glm_vec_rotate(v1, glm_rad(45), (vec3){1.0f, 0.0f, 0.0f});
```
some functions are overloaded :) e.g you can normalize vector:
```C
glm_vec_normalize(vec);
```
this will normalize vec and store normalized vector into `vec` but if you will store normalized vector into another vector do this:
```C
glm_vec_normalize_to(vec, result);
```
like this function you may see `_to` postfix, this functions store results to another variables and save temp memory


to call pre-compiled versions include header with `c` postfix, c means call. Pre-compiled versions are just wrappers.
```C
#include <cglm/call.h>
```
this header will include all heaers with c postfix. You need to call functions with c posfix:
```C
glmc_vec_normalize(vec);
```

Function usage and parameters are documented inside related headers. You may see same parameter passed twice in some examples like this:
```C
glm_mat4_mul(m1, m2, m1);

/* or */
glm_mat4_mul(m1, m1, m1);
```
the first two parameter are **[in]** and the last one is **[out]** parameter. After multiplied *m1* and *m2* the result is stored in *m1*. This is why we send *m1* twice. You may store result in different matrix, this just an example.

## How to send matrix to OpenGL

mat4 is array of vec4 and vec4 is array of floats. `glUniformMatrix4fv` functions accecpts `float*` as `value` (last param), so you can cast mat4 to float* or you can pass first column of matrix as beginning of memory of matrix:

Option 1: Send first column
```C
glUniformMatrix4fv(location, 1, GL_FALSE, matrix[0]);

/* array of matrices */
glUniformMatrix4fv(location, 1, GL_FALSE, matrix[0][0]);
```

Option 2: Cast matrix to pointer type (also valid for multiple dimensional arrays)
```C
glUniformMatrix4fv(location, 1, GL_FALSE, (float *)matrix);
```

You can pass same way to another APIs e.g. Vulkan, DX... 

## Notes

- This library uses float types only, does not support Integers, Double... yet
- If headers are not working properly with your compiler, IDE please open an issue, because I'm using GCC and clang to test it maybe sometimes MSVC

**TODO:**
- [ ] Unit tests (In Progress)
- [ ] Unit tests for comparing cglm with glm results
- [x] Add version info
- [ ] Unaligned operations (e.g. `glm_umat4_mul`)
- [ ] Extra documentation
- [ ] ARM Neon Arch (In Progress)