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.. default-domain:: C
frustum
=============
Header: cglm/frustum.h
cglm provides convenient functions to extract frustum planes, corners...
All extracted corners are **vec4** so you must create array of **vec4**
not **vec3**. If you want to store them to save space you msut convert them
yourself.
**vec4** is used to speed up functions need to corners. This is why frustum
fucntions use *vec4* instead of *vec3*
Currenty related-functions use [-1, 1] clip space configuration to extract
corners but you can override it by prodiving **GLM_CUSTOM_CLIPSPACE** macro.
If you provide it then you have to all bottom macros as *vec4*
Current configuration:
.. code-block:: c
/* near */
GLM_CSCOORD_LBN {-1.0f, -1.0f, -1.0f, 1.0f}
GLM_CSCOORD_LTN {-1.0f, 1.0f, -1.0f, 1.0f}
GLM_CSCOORD_RTN { 1.0f, 1.0f, -1.0f, 1.0f}
GLM_CSCOORD_RBN { 1.0f, -1.0f, -1.0f, 1.0f}
/* far */
GLM_CSCOORD_LBF {-1.0f, -1.0f, 1.0f, 1.0f}
GLM_CSCOORD_LTF {-1.0f, 1.0f, 1.0f, 1.0f}
GLM_CSCOORD_RTF { 1.0f, 1.0f, 1.0f, 1.0f}
GLM_CSCOORD_RBF { 1.0f, -1.0f, 1.0f, 1.0f}
Explain of short names:
* **LBN**: left bottom near
* **LTN**: left top near
* **RTN**: right top near
* **RBN**: right bottom near
* **LBF**: left bottom far
* **LTF**: left top far
* **RTF**: right top far
* **RBF**: right bottom far
Table of contents (click to go):
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Macros:
.. code-block:: c
GLM_LBN 0 /* left bottom near */
GLM_LTN 1 /* left top near */
GLM_RTN 2 /* right top near */
GLM_RBN 3 /* right bottom near */
GLM_LBF 4 /* left bottom far */
GLM_LTF 5 /* left top far */
GLM_RTF 6 /* right top far */
GLM_RBF 7 /* right bottom far */
GLM_LEFT 0
GLM_RIGHT 1
GLM_BOTTOM 2
GLM_TOP 3
GLM_NEAR 4
GLM_FAR 5
Functions:
1. :c:func:`glm_frustum_planes`
#. :c:func:`glm_frustum_corners`
#. :c:func:`glm_frustum_center`
#. :c:func:`glm_frustum_box`
#. :c:func:`glm_frustum_corners_at`
Functions documentation
~~~~~~~~~~~~~~~~~~~~~~~
.. c:function:: void glm_frustum_planes(mat4 m, vec4 dest[6])
| extracts view frustum planes
planes' space:
- if m = proj: View Space
- if m = viewProj: World Space
- if m = MVP: Object Space
You probably want to extract planes in world space so use viewProj as m
Computing viewProj:
.. code-block:: c
glm_mat4_mul(proj, view, viewProj);
Exracted planes order: [left, right, bottom, top, near, far]
Parameters:
| *[in]* **m** matrix
| *[out]* **dest** exracted view frustum planes
.. c:function:: void glm_frustum_corners(mat4 invMat, vec4 dest[8])
| extracts view frustum corners using clip-space coordinates
corners' space:
- if m = invViewProj: World Space
- if m = invMVP: Object Space
You probably want to extract corners in world space so use **invViewProj**
Computing invViewProj:
.. code-block:: c
glm_mat4_mul(proj, view, viewProj);
...
glm_mat4_inv(viewProj, invViewProj);
if you have a near coord at **i** index,
you can get it's far coord by i + 4;
follow example below to understand that
For instance to find center coordinates between a near and its far coord:
.. code-block:: c
for (j = 0; j < 4; j++) {
glm_vec3_center(corners[i], corners[i + 4], centerCorners[i]);
}
corners[i + 4] is far of corners[i] point.
Parameters:
| *[in]* **invMat** matrix
| *[out]* **dest** exracted view frustum corners
.. c:function:: void glm_frustum_center(vec4 corners[8], vec4 dest)
| finds center of view frustum
Parameters:
| *[in]* **corners** view frustum corners
| *[out]* **dest** view frustum center
.. c:function:: void glm_frustum_box(vec4 corners[8], mat4 m, vec3 box[2])
| finds bounding box of frustum relative to given matrix e.g. view mat
Parameters:
| *[in]* **corners** view frustum corners
| *[in]* **m** matrix to convert existing conners
| *[out]* **box** bounding box as array [min, max]
.. c:function:: void glm_frustum_corners_at(vec4 corners[8], float splitDist, float farDist, vec4 planeCorners[4])
| finds planes corners which is between near and far planes (parallel)
this will be helpful if you want to split a frustum e.g. CSM/PSSM. This will
find planes' corners but you will need to one more plane.
Actually you have it, it is near, far or created previously with this func ;)
Parameters:
| *[in]* **corners** frustum corners
| *[in]* **splitDist** split distance
| *[in]* **farDist** far distance (zFar)
| *[out]* **planeCorners** plane corners [LB, LT, RT, RB]
|
