Matrices¶

API for initializing and manipulating 4x4 matrices

c_matrix_t¶

A c_matrix_t holds a 4x4 transform matrix. This is a single precision, column-major matrix which means it is compatible with what OpenGL expects.

A c_matrix_t can represent transforms such as, rotations, scaling, translation, sheering, and linear projections. You can combine these transforms by multiplying multiple matrices in the order you want them applied.

The transformation of a vertex (x, y, z, w) by a c_matrix_t is given by:

x_new = xx * x + xy * y + xz * z + xw * w
y_new = yx * x + yy * y + yz * z + yw * w
z_new = zx * x + zy * y + zz * z + zw * w
w_new = wx * x + wy * y + wz * z + ww * w

Where w is normally 1

Note

You must consider the members of the c_matrix_t structure read only, and all matrix modifications must be done via the c_matrix API. This allows clib to annotate the matrices internally. Violation of this will give undefined results. If you need to initialize a matrix with a constant other than the identity matrix you can use c_matrix_init_from_array().

void c_matrix_init_identity(c_matrix_t *matrix)¶

Parameters:	matrix – A 4x4 transformation matrix

Resets matrix to the identity matrix:

.xx=1; .xy=0; .xz=0; .xw=0;
.yx=0; .yy=1; .yz=0; .yw=0;
.zx=0; .zy=0; .zz=1; .zw=0;
.wx=0; .wy=0; .wz=0; .ww=1;

void c_matrix_init_translation(c_matrix_t *matrix, float tx, float ty, float tz)¶

Parameters:	matrix – A 4x4 transformation matrix tx – x coordinate of the translation vector ty – y coordinate of the translation vector tz – z coordinate of the translation vector

Resets matrix to the (tx, ty, tz) translation matrix:

.xx=1; .xy=0; .xz=0; .xw=tx;
.yx=0; .yy=1; .yz=0; .yw=ty;
.zx=0; .zy=0; .zz=1; .zw=tz;
.wx=0; .wy=0; .wz=0; .ww=1;

void c_matrix_multiply(c_matrix_t *result, const c_matrix_t *a, const c_matrix_t *b)¶

Parameters:	result – The address of a 4x4 matrix to store the result in a – A 4x4 transformation matrix b – A 4x4 transformation matrix

Multiplies the two supplied matrices together and stores the resulting matrix inside result.

Note

It is possible to multiply the a matrix in-place, so result can be equal to a but can’t be equal to b.

void c_matrix_rotate(c_matrix_t *matrix, float angle, float x, float y, float z)¶

Parameters:	matrix – A 4x4 transformation matrix angle – The angle you want to rotate in degrees x – X component of your rotation vector y – Y component of your rotation vector z – Z component of your rotation vector

Multiplies matrix with a rotation matrix that applies a rotation of angle degrees around the specified 3D vector.

void c_matrix_rotate_quaternion(c_matrix_t *matrix, const c_quaternion_t *quaternion)¶

Parameters:	matrix – A 4x4 transformation matrix quaternion – A quaternion describing a rotation

Multiplies matrix with a rotation transformation described by the given c_quaternion_t.

void c_matrix_rotate_euler(c_matrix_t *matrix, const c_euler_t *euler)¶

Parameters:	matrix – A 4x4 transformation matrix euler – A euler describing a rotation

Multiplies matrix with a rotation transformation described by the given c_euler_t.

void c_matrix_translate(c_matrix_t *matrix, float x, float y, float z)¶

Parameters:	matrix – A 4x4 transformation matrix x – The X translation you want to apply y – The Y translation you want to apply z – The Z translation you want to apply

Multiplies matrix with a transform matrix that translates along the X, Y and Z axis.

void c_matrix_scale(c_matrix_t *matrix, float sx, float sy, float sz)¶

Parameters:	matrix – A 4x4 transformation matrix sx – The X scale factor sy – The Y scale factor sz – The Z scale factor

Multiplies matrix with a transform matrix that scales along the X, Y and Z axis.

void c_matrix_look_at(c_matrix_t *matrix, float eye_position_x, float eye_position_y, float eye_position_z, float object_x, float object_y, float object_z, float world_up_x, float world_up_y, float world_up_z)¶

Parameters:

matrix – A 4x4 transformation matrix eye_position_x – The X coordinate to look from eye_position_y – The Y coordinate to look from eye_position_z – The Z coordinate to look from object_x – The X coordinate of the object to look at object_y – The Y coordinate of the object to look at object_z – The Z coordinate of the object to look at world_up_x – The X component of the world’s up direction vector world_up_y – The Y component of the world’s up direction vector world_up_z – The Z component of the world’s up direction vector

Applies a view transform matrix that positions the camera at the coordinate (eye_position_x, eye_position_y, eye_position_z) looking towards an object at the coordinate (object_x, object_y, object_z). The top of the camera is aligned to the given world up vector, which is normally simply (0, 1, 0) to map up to the positive direction of the y axis.

Because there is a lot of missleading documentation online for gluLookAt regarding the up vector we want to try and be a bit clearer here.

The up vector should simply be relative to your world coordinates and does not need to change as you move the eye and object positions. Many online sources may claim that the up vector needs to be perpendicular to the vector between the eye and object position (partly because the man page is somewhat missleading) but that is not necessary for this function.

Note

You should never look directly along the world-up vector.

Note

It is assumed you are using a typical projection matrix where your origin maps to the center of your viewport.

Note

Almost always when you use this function it should be the first transform applied to a new modelview transform

void c_matrix_frustum(c_matrix_t *matrix, float left, float right, float bottom, float top, float z_near, float z_far)¶

Parameters:

matrix – A 4x4 transformation matrix left – X position of the left clipping plane where it intersects the near clipping plane right – X position of the right clipping plane where it intersects the near clipping plane bottom – Y position of the bottom clipping plane where it intersects the near clipping plane top – Y position of the top clipping plane where it intersects the near clipping plane z_near – The distance to the near clipping plane (Must be positive) z_far – The distance to the far clipping plane (Must be positive)

Multiplies matrix by the given frustum perspective matrix.

void c_matrix_perspective(c_matrix_t *matrix, float fov_y, float aspect, float z_near, float z_far)¶

Parameters:	matrix – A 4x4 transformation matrix fov_y – Vertical field of view angle in degrees. aspect – The (width over height) aspect ratio for display z_near – The distance to the near clipping plane (Must be positive, and must not be 0) z_far – The distance to the far clipping plane (Must be positive)

Multiplies matrix by the described perspective matrix

Note

You should be careful not to have to great a z_far / z_near ratio since that will reduce the effectiveness of depth testing since there wont be enough precision to identify the depth of objects near to each other.

void c_matrix_orthographic(c_matrix_t *matrix, float x_1, float y_1, float x_2, float y_2, float near, float far)¶

Parameters:

matrix – A 4x4 transformation matrix x_1 – The x coordinate for the first vertical clipping plane y_1 – The y coordinate for the first horizontal clipping plane x_2 – The x coordinate for the second vertical clipping plane y_2 – The y coordinate for the second horizontal clipping plane near – The distance to the near clipping plane (will be negative if the plane is behind the viewer) far – The distance to the far clipping plane (will be negative if the plane is behind the viewer)

Multiplies matrix by a parallel projection matrix.

void c_matrix_view_2d_in_frustum(c_matrix_t *matrix, float left, float right, float bottom, float top, float z_near, float z_2d, float width_2d, float height_2d)¶

Parameters:

matrix – A 4x4 transformation matrix left – coord of left vertical clipping plane right – coord of right vertical clipping plane bottom – coord of bottom horizontal clipping plane top – coord of top horizontal clipping plane z_near – The distance to the near clip plane. Never pass 0 and always pass a positive number. z_2d – The distance to the 2D plane. (Should always be positive and be between z_near and the z_far value that was passed to c_matrix_frustum()) width_2d – The width of the 2D coordinate system height_2d – The height of the 2D coordinate system

Multiplies matrix by a view transform that maps the 2D coordinates (0,0) top left and (width_2d,:c:data:height_2d) bottom right the full viewport size. Geometry at a depth of 0 will now lie on this 2D plane.

Note

this doesn’t multiply the matrix by any projection matrix, but it assumes you have a perspective projection as defined by passing the corresponding arguments to c_matrix_frustum().

Toolkits such as Clutter that mix 2D and 3D drawing can use this to create a 2D coordinate system within a 3D perspective projected view frustum.

void c_matrix_view_2d_in_perspective(c_matrix_t *matrix, float fov_y, float aspect, float z_near, float z_2d, float width_2d, float height_2d)¶

Parameters:

fov_y – A field of view angle for the Y axis aspect – The ratio of width to height determining the field of view angle for the x axis. z_near – The distance to the near clip plane. Never pass 0 and always pass a positive number. z_2d – The distance to the 2D plane. (Should always be positive and be between z_near and the z_far value that was passed to c_matrix_frustum()) width_2d – The width of the 2D coordinate system height_2d – The height of the 2D coordinate system

Multiplies matrix by a view transform that maps the 2D coordinates (0,0) top left and (width_2d,:c:data:height_2d) bottom right the full viewport size. Geometry at a depth of 0 will now lie on this 2D plane.

Note

this doesn’t multiply the matrix by any projection matrix, but it assumes you have a perspective projection as defined by passing the corresponding arguments to c_matrix_perspective().

Toolkits such as Clutter that mix 2D and 3D drawing can use this to create a 2D coordinate system within a 3D perspective projected view frustum.

void c_matrix_init_from_array(c_matrix_t *matrix, const float *array)¶

Parameters:	matrix – A 4x4 transformation matrix array – A linear array of 16 floats (column-major order)

Initializes matrix with the contents of array

const float *c_matrix_get_array(const c_matrix_t *matrix)¶

Parameters:	matrix – A 4x4 transformation matrix

Casts matrix to a float array which can be directly passed to OpenGL.

Returns:	a pointer to the float array

void c_matrix_init_from_quaternion(c_matrix_t *matrix, const c_quaternion_t *quaternion)¶

Parameters:	matrix – A 4x4 transformation matrix quaternion – A c_quaternion_t

Initializes matrix from a c_quaternion_t rotation.

void c_matrix_init_from_euler(c_matrix_t *matrix, const c_euler_t *euler)¶

Parameters:	matrix – A 4x4 transformation matrix euler – A c_euler_t

Initializes matrix from a c_euler_t rotation.

_Bool c_matrix_equal(const void *v1, const void *v2)¶

Parameters:	v1 – A 4x4 transformation matrix v2 – A 4x4 transformation matrix

Compares two matrices to see if they represent the same transformation. Although internally the matrices may have different annotations associated with them and may potentially have a cached inverse matrix these are not considered in the comparison.

c_matrix_t *c_matrix_copy(const c_matrix_t *matrix)¶

Parameters:	matrix – A 4x4 transformation matrix you want to copy

Allocates a new c_matrix_t on the heap and initializes it with the same values as matrix.

Returns:	(transfer full): A newly allocated c_matrix_t which

should be freed using c_matrix_free()

void c_matrix_free(c_matrix_t *matrix)¶

Parameters:	matrix – A 4x4 transformation matrix you want to free

Frees a c_matrix_t that was previously allocated via a call to c_matrix_copy().

_Bool c_matrix_get_inverse(const c_matrix_t *matrix, c_matrix_t *inverse)¶

Parameters:	matrix – A 4x4 transformation matrix inverse – (out): The destination for a 4x4 inverse transformation matrix

Gets the inverse transform of a given matrix and uses it to initialize a new c_matrix_t.

Note

Although the first parameter is annotated as const to indicate that the transform it represents isn’t modified this function may technically save a copy of the inverse transform within the given c_matrix_t so that subsequent requests for the inverse transform may avoid costly inversion calculations.

Returns:	true if the inverse was successfully calculated or false for degenerate transformations that can’t be inverted (in this case the inverse matrix will simply be initialized with the identity matrix)

void c_matrix_transform_point(const c_matrix_t *matrix, float *x, float *y, float *z, float *w)¶

Parameters:	matrix – A 4x4 transformation matrix x – (inout): The X component of your points position y – (inout): The Y component of your points position z – (inout): The Z component of your points position w – (inout): The W component of your points position

Transforms a point whos position is given and returned as four float components.

void c_matrix_transform_points(const c_matrix_t *matrix, int n_components, size_t stride_in, const void *points_in, size_t stride_out, void *points_out, int n_points)¶

Parameters:

matrix – A transformation matrix n_components – The number of position components for each input point. (either 2 or 3) stride_in – The stride in bytes between input points. points_in – A pointer to the first component of the first input point. stride_out – The stride in bytes between output points. points_out – A pointer to the first component of the first output point. n_points – The number of points to transform.

Transforms an array of input points and writes the result to another array of output points. The input points can either have 2 or 3 components each. The output points always have 3 components. The output array can simply point to the input array to do the transform in-place.

If you need to transform 4 component points see c_matrix_project_points().

Here’s an example with differing input/output strides:

typedef struct {
  float x,y;
  uint8_t r,g,b,a;
  float s,t,p;
} MyInVertex;
typedef struct {
  uint8_t r,g,b,a;
  float x,y,z;
} MyOutVertex;
MyInVertex vertices[N_VERTICES];
MyOutVertex results[N_VERTICES];
c_matrix_t matrix;

my_load_vertices (vertices);
my_get_matrix (&matrix);

c_matrix_transform_points (&matrix,
                              2,
                              sizeof (MyInVertex),
                              &vertices[0].x,
                              sizeof (MyOutVertex),
                              &results[0].x,
                              N_VERTICES);

void c_matrix_project_points(const c_matrix_t *matrix, int n_components, size_t stride_in, const void *points_in, size_t stride_out, void *points_out, int n_points)¶

Parameters:

matrix – A projection matrix n_components – The number of position components for each input point. (either 2, 3 or 4) stride_in – The stride in bytes between input points. points_in – A pointer to the first component of the first input point. stride_out – The stride in bytes between output points. points_out – A pointer to the first component of the first output point. n_points – The number of points to transform.

Projects an array of input points and writes the result to another array of output points. The input points can either have 2, 3 or 4 components each. The output points always have 4 components (known as homogenous coordinates). The output array can simply point to the input array to do the transform in-place.

Here’s an example with differing input/output strides:

typedef struct {
  float x,y;
  uint8_t r,g,b,a;
  float s,t,p;
} MyInVertex;
typedef struct {
  uint8_t r,g,b,a;
  float x,y,z;
} MyOutVertex;
MyInVertex vertices[N_VERTICES];
MyOutVertex results[N_VERTICES];
c_matrix_t matrix;

my_load_vertices (vertices);
my_get_matrix (&matrix);

c_matrix_project_points (&matrix,
                            2,
                            sizeof (MyInVertex),
                            &vertices[0].x,
                            sizeof (MyOutVertex),
                            &results[0].x,
                            N_VERTICES);

_Bool c_matrix_is_identity(const c_matrix_t *matrix)¶

Parameters:	matrix – A c_matrix_t

Determines if the given matrix is an identity matrix.

Returns:	true if matrix is an identity matrix else false

void c_matrix_transpose(c_matrix_t *matrix)¶

Parameters:	matrix – A c_matrix_t

Replaces matrix with its transpose. Ie, every element (i,j) in the new matrix is taken from element (j,i) in the old matrix.

void c_matrix_print(const c_matrix_t *matrix)¶

Parameters:	matrix (const c_matrix_t *) –

void c_matrix_prefix_print(const char *prefix, const c_matrix_t *matrix)¶

Parameters:	prefix (const char *) – matrix (const c_matrix_t *) –

void c_matrix_init_identity(c_matrix_t *matrix)

Parameters:	matrix – A 4x4 transformation matrix

Resets matrix to the identity matrix:

.xx=1; .xy=0; .xz=0; .xw=0;
.yx=0; .yy=1; .yz=0; .yw=0;
.zx=0; .zy=0; .zz=1; .zw=0;
.wx=0; .wy=0; .wz=0; .ww=1;

void c_matrix_init_translation(c_matrix_t *matrix, float tx, float ty, float tz)

Parameters:	matrix – A 4x4 transformation matrix tx – x coordinate of the translation vector ty – y coordinate of the translation vector tz – z coordinate of the translation vector

Resets matrix to the (tx, ty, tz) translation matrix:

.xx=1; .xy=0; .xz=0; .xw=tx;
.yx=0; .yy=1; .yz=0; .yw=ty;
.zx=0; .zy=0; .zz=1; .zw=tz;
.wx=0; .wy=0; .wz=0; .ww=1;

void c_matrix_multiply(c_matrix_t *result, const c_matrix_t *a, const c_matrix_t *b)

Parameters:	result – The address of a 4x4 matrix to store the result in a – A 4x4 transformation matrix b – A 4x4 transformation matrix

Multiplies the two supplied matrices together and stores the resulting matrix inside result.

Note

It is possible to multiply the a matrix in-place, so result can be equal to a but can’t be equal to b.

void c_matrix_rotate(c_matrix_t *matrix, float angle, float x, float y, float z)

Parameters:	matrix – A 4x4 transformation matrix angle – The angle you want to rotate in degrees x – X component of your rotation vector y – Y component of your rotation vector z – Z component of your rotation vector

Multiplies matrix with a rotation matrix that applies a rotation of angle degrees around the specified 3D vector.

void c_matrix_rotate_quaternion(c_matrix_t *matrix, const c_quaternion_t *quaternion)

Parameters:	matrix – A 4x4 transformation matrix quaternion – A quaternion describing a rotation

Multiplies matrix with a rotation transformation described by the given c_quaternion_t.

void c_matrix_rotate_euler(c_matrix_t *matrix, const c_euler_t *euler)

Parameters:	matrix – A 4x4 transformation matrix euler – A euler describing a rotation

Multiplies matrix with a rotation transformation described by the given c_euler_t.

void c_matrix_translate(c_matrix_t *matrix, float x, float y, float z)

Parameters:	matrix – A 4x4 transformation matrix x – The X translation you want to apply y – The Y translation you want to apply z – The Z translation you want to apply

Multiplies matrix with a transform matrix that translates along the X, Y and Z axis.

void c_matrix_scale(c_matrix_t *matrix, float sx, float sy, float sz)

Parameters:	matrix – A 4x4 transformation matrix sx – The X scale factor sy – The Y scale factor sz – The Z scale factor

Multiplies matrix with a transform matrix that scales along the X, Y and Z axis.

void c_matrix_look_at(c_matrix_t *matrix, float eye_position_x, float eye_position_y, float eye_position_z, float object_x, float object_y, float object_z, float world_up_x, float world_up_y, float world_up_z)

Parameters:

matrix – A 4x4 transformation matrix eye_position_x – The X coordinate to look from eye_position_y – The Y coordinate to look from eye_position_z – The Z coordinate to look from object_x – The X coordinate of the object to look at object_y – The Y coordinate of the object to look at object_z – The Z coordinate of the object to look at world_up_x – The X component of the world’s up direction vector world_up_y – The Y component of the world’s up direction vector world_up_z – The Z component of the world’s up direction vector

Applies a view transform matrix that positions the camera at the coordinate (eye_position_x, eye_position_y, eye_position_z) looking towards an object at the coordinate (object_x, object_y, object_z). The top of the camera is aligned to the given world up vector, which is normally simply (0, 1, 0) to map up to the positive direction of the y axis.

Because there is a lot of missleading documentation online for gluLookAt regarding the up vector we want to try and be a bit clearer here.

The up vector should simply be relative to your world coordinates and does not need to change as you move the eye and object positions. Many online sources may claim that the up vector needs to be perpendicular to the vector between the eye and object position (partly because the man page is somewhat missleading) but that is not necessary for this function.

Note

You should never look directly along the world-up vector.

Note

It is assumed you are using a typical projection matrix where your origin maps to the center of your viewport.

Note

Almost always when you use this function it should be the first transform applied to a new modelview transform

void c_matrix_frustum(c_matrix_t *matrix, float left, float right, float bottom, float top, float z_near, float z_far)

Parameters:

matrix – A 4x4 transformation matrix left – X position of the left clipping plane where it intersects the near clipping plane right – X position of the right clipping plane where it intersects the near clipping plane bottom – Y position of the bottom clipping plane where it intersects the near clipping plane top – Y position of the top clipping plane where it intersects the near clipping plane z_near – The distance to the near clipping plane (Must be positive) z_far – The distance to the far clipping plane (Must be positive)

Multiplies matrix by the given frustum perspective matrix.

void c_matrix_perspective(c_matrix_t *matrix, float fov_y, float aspect, float z_near, float z_far)

Parameters:	matrix – A 4x4 transformation matrix fov_y – Vertical field of view angle in degrees. aspect – The (width over height) aspect ratio for display z_near – The distance to the near clipping plane (Must be positive, and must not be 0) z_far – The distance to the far clipping plane (Must be positive)

Multiplies matrix by the described perspective matrix

Note

You should be careful not to have to great a z_far / z_near ratio since that will reduce the effectiveness of depth testing since there wont be enough precision to identify the depth of objects near to each other.

void c_matrix_orthographic(c_matrix_t *matrix, float x_1, float y_1, float x_2, float y_2, float near, float far)

Parameters:

matrix – A 4x4 transformation matrix x_1 – The x coordinate for the first vertical clipping plane y_1 – The y coordinate for the first horizontal clipping plane x_2 – The x coordinate for the second vertical clipping plane y_2 – The y coordinate for the second horizontal clipping plane near – The distance to the near clipping plane (will be negative if the plane is behind the viewer) far – The distance to the far clipping plane (will be negative if the plane is behind the viewer)

Multiplies matrix by a parallel projection matrix.

void c_matrix_view_2d_in_frustum(c_matrix_t *matrix, float left, float right, float bottom, float top, float z_near, float z_2d, float width_2d, float height_2d)

Parameters:

matrix – A 4x4 transformation matrix left – coord of left vertical clipping plane right – coord of right vertical clipping plane bottom – coord of bottom horizontal clipping plane top – coord of top horizontal clipping plane z_near – The distance to the near clip plane. Never pass 0 and always pass a positive number. z_2d – The distance to the 2D plane. (Should always be positive and be between z_near and the z_far value that was passed to c_matrix_frustum()) width_2d – The width of the 2D coordinate system height_2d – The height of the 2D coordinate system

Multiplies matrix by a view transform that maps the 2D coordinates (0,0) top left and (width_2d,:c:data:height_2d) bottom right the full viewport size. Geometry at a depth of 0 will now lie on this 2D plane.

Note

this doesn’t multiply the matrix by any projection matrix, but it assumes you have a perspective projection as defined by passing the corresponding arguments to c_matrix_frustum().

Toolkits such as Clutter that mix 2D and 3D drawing can use this to create a 2D coordinate system within a 3D perspective projected view frustum.

void c_matrix_view_2d_in_perspective(c_matrix_t *matrix, float fov_y, float aspect, float z_near, float z_2d, float width_2d, float height_2d)

Parameters:

fov_y – A field of view angle for the Y axis aspect – The ratio of width to height determining the field of view angle for the x axis. z_near – The distance to the near clip plane. Never pass 0 and always pass a positive number. z_2d – The distance to the 2D plane. (Should always be positive and be between z_near and the z_far value that was passed to c_matrix_frustum()) width_2d – The width of the 2D coordinate system height_2d – The height of the 2D coordinate system

Multiplies matrix by a view transform that maps the 2D coordinates (0,0) top left and (width_2d,:c:data:height_2d) bottom right the full viewport size. Geometry at a depth of 0 will now lie on this 2D plane.

Note

this doesn’t multiply the matrix by any projection matrix, but it assumes you have a perspective projection as defined by passing the corresponding arguments to c_matrix_perspective().

Toolkits such as Clutter that mix 2D and 3D drawing can use this to create a 2D coordinate system within a 3D perspective projected view frustum.

void c_matrix_init_from_array(c_matrix_t *matrix, const float *array)

Parameters:	matrix – A 4x4 transformation matrix array – A linear array of 16 floats (column-major order)

Initializes matrix with the contents of array

const float *c_matrix_get_array(const c_matrix_t *matrix)

Parameters:	matrix – A 4x4 transformation matrix

Casts matrix to a float array which can be directly passed to OpenGL.

Returns:	a pointer to the float array

void c_matrix_init_from_quaternion(c_matrix_t *matrix, const c_quaternion_t *quaternion)

Parameters:	matrix – A 4x4 transformation matrix quaternion – A c_quaternion_t

Initializes matrix from a c_quaternion_t rotation.

void c_matrix_init_from_euler(c_matrix_t *matrix, const c_euler_t *euler)

Parameters:	matrix – A 4x4 transformation matrix euler – A c_euler_t

Initializes matrix from a c_euler_t rotation.

_Bool c_matrix_equal(const void *v1, const void *v2)

Parameters:	v1 – A 4x4 transformation matrix v2 – A 4x4 transformation matrix

Compares two matrices to see if they represent the same transformation. Although internally the matrices may have different annotations associated with them and may potentially have a cached inverse matrix these are not considered in the comparison.

c_matrix_t *c_matrix_copy(const c_matrix_t *matrix)

Parameters:	matrix – A 4x4 transformation matrix you want to copy

Allocates a new c_matrix_t on the heap and initializes it with the same values as matrix.

Returns:	(transfer full): A newly allocated c_matrix_t which

should be freed using c_matrix_free()

void c_matrix_free(c_matrix_t *matrix)

Parameters:	matrix – A 4x4 transformation matrix you want to free

Frees a c_matrix_t that was previously allocated via a call to c_matrix_copy().

_Bool c_matrix_get_inverse(const c_matrix_t *matrix, c_matrix_t *inverse)

Parameters:	matrix – A 4x4 transformation matrix inverse – (out): The destination for a 4x4 inverse transformation matrix

Gets the inverse transform of a given matrix and uses it to initialize a new c_matrix_t.

Note

Although the first parameter is annotated as const to indicate that the transform it represents isn’t modified this function may technically save a copy of the inverse transform within the given c_matrix_t so that subsequent requests for the inverse transform may avoid costly inversion calculations.

Returns:	true if the inverse was successfully calculated or false for degenerate transformations that can’t be inverted (in this case the inverse matrix will simply be initialized with the identity matrix)

void c_matrix_transform_point(const c_matrix_t *matrix, float *x, float *y, float *z, float *w)

Parameters:	matrix – A 4x4 transformation matrix x – (inout): The X component of your points position y – (inout): The Y component of your points position z – (inout): The Z component of your points position w – (inout): The W component of your points position

Transforms a point whos position is given and returned as four float components.

void c_matrix_transform_points(const c_matrix_t *matrix, int n_components, size_t stride_in, const void *points_in, size_t stride_out, void *points_out, int n_points)

Parameters:

matrix – A transformation matrix n_components – The number of position components for each input point. (either 2 or 3) stride_in – The stride in bytes between input points. points_in – A pointer to the first component of the first input point. stride_out – The stride in bytes between output points. points_out – A pointer to the first component of the first output point. n_points – The number of points to transform.

Transforms an array of input points and writes the result to another array of output points. The input points can either have 2 or 3 components each. The output points always have 3 components. The output array can simply point to the input array to do the transform in-place.

If you need to transform 4 component points see c_matrix_project_points().

Here’s an example with differing input/output strides:

typedef struct {
  float x,y;
  uint8_t r,g,b,a;
  float s,t,p;
} MyInVertex;
typedef struct {
  uint8_t r,g,b,a;
  float x,y,z;
} MyOutVertex;
MyInVertex vertices[N_VERTICES];
MyOutVertex results[N_VERTICES];
c_matrix_t matrix;

my_load_vertices (vertices);
my_get_matrix (&matrix);

c_matrix_transform_points (&matrix,
                              2,
                              sizeof (MyInVertex),
                              &vertices[0].x,
                              sizeof (MyOutVertex),
                              &results[0].x,
                              N_VERTICES);

void c_matrix_project_points(const c_matrix_t *matrix, int n_components, size_t stride_in, const void *points_in, size_t stride_out, void *points_out, int n_points)

Parameters:

matrix – A projection matrix n_components – The number of position components for each input point. (either 2, 3 or 4) stride_in – The stride in bytes between input points. points_in – A pointer to the first component of the first input point. stride_out – The stride in bytes between output points. points_out – A pointer to the first component of the first output point. n_points – The number of points to transform.

Projects an array of input points and writes the result to another array of output points. The input points can either have 2, 3 or 4 components each. The output points always have 4 components (known as homogenous coordinates). The output array can simply point to the input array to do the transform in-place.

Here’s an example with differing input/output strides:

typedef struct {
  float x,y;
  uint8_t r,g,b,a;
  float s,t,p;
} MyInVertex;
typedef struct {
  uint8_t r,g,b,a;
  float x,y,z;
} MyOutVertex;
MyInVertex vertices[N_VERTICES];
MyOutVertex results[N_VERTICES];
c_matrix_t matrix;

my_load_vertices (vertices);
my_get_matrix (&matrix);

c_matrix_project_points (&matrix,
                            2,
                            sizeof (MyInVertex),
                            &vertices[0].x,
                            sizeof (MyOutVertex),
                            &results[0].x,
                            N_VERTICES);

_Bool c_matrix_is_identity(const c_matrix_t *matrix)

Parameters:	matrix – A c_matrix_t

Determines if the given matrix is an identity matrix.

Returns:	true if matrix is an identity matrix else false

void c_matrix_transpose(c_matrix_t *matrix)

Parameters:	matrix – A c_matrix_t

Replaces matrix with its transpose. Ie, every element (i,j) in the new matrix is taken from element (j,i) in the old matrix.

void c_matrix_print(const c_matrix_t *matrix)

Parameters:	matrix (const c_matrix_t *) –

void c_matrix_prefix_print(const char *prefix, const c_matrix_t *matrix)

Parameters:	prefix (const char *) – matrix (const c_matrix_t *) –