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cam: extend frustum's far distance helper (#71)

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* this will help to implement zoom easily
This commit is contained in:
Recep Aslantas
2019-01-16 14:59:58 +03:00
committed by GitHub
parent e3d3cd8ab8
commit 07e60bd098
4 changed files with 45 additions and 0 deletions
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4
include/cglm/call/cam.h
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@@ -61,6 +61,10 @@ glmc_perspective(float fovy,
float farVal,
mat4 dest);
CGLM_EXPORT
void
glmc_persp_move_far(mat4 proj, float deltaFar);
CGLM_EXPORT
void
glmc_perspective_default(float aspect, mat4 dest);

24
include/cglm/cam.h
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@@ -271,6 +271,30 @@ glm_perspective(float fovy,
dest[3][2] = 2.0f * nearVal * farVal * fn;
}
/*!
* @brief extend perspective projection matrix's far distance
*
* this function does not guarantee far >= near, be aware of that!
*
* @param[in, out] proj projection matrix to extend
* @param[in] deltaFar distance from existing far (negative to shink)
*/
CGLM_INLINE
void
glm_persp_move_far(mat4 proj, float deltaFar) {
float fn, farVal, nearVal, p22, p32;
p22 = proj[2][2];
p32 = proj[3][2];
nearVal = p32 / (p22 - 1.0f);
farVal = p32 / (p22 + 1.0f) + deltaFar;
fn = 1.0f / (nearVal - farVal);
proj[2][2] = (nearVal + farVal) * fn;
proj[3][2] = 2.0f * nearVal * farVal * fn;
}
/*!
* @brief set up perspective projection matrix with default near/far
* and angle values