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Left-handed and Right-handed Look-At Matrix functions (#17)

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Thompson Lee 2016-08-04 06:43:33 -04:00 committed by fincs
parent 8481109e15
commit dde8877f38
2 changed files with 62 additions and 0 deletions
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11
include/c3d/maths.h
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@ -453,6 +453,17 @@ void Mtx_PerspTilt(C3D_Mtx* mtx, float fovy, float aspect, float near, float far
* @param[in] screen Focal length
*/
void Mtx_PerspStereoTilt(C3D_Mtx* mtx, float fovy, float aspect, float near, float far, float iod, float screen);
/**
* @brief Left-handed Look-At matrix, using DirectX implementation
* @note See https://msdn.microsoft.com/en-us/library/windows/desktop/bb205342
* @param[out] out Output matrix.
* @param[in] cameraPosition Position of the intended camera in 3D space.
* @param[in] cameraTarget Position of the intended target the camera is supposed to face in 3D space.
* @param[in] cameraUpVector The vector that points straight up depending on the camera's "Up" direction.
* @param[in] isLeftHanded If true, output matrix is left-handed. If false, output matrix is right-handed.
*/
void Mtx_LookAt(C3D_Mtx* out, C3D_FVec cameraPosition, C3D_FVec cameraTarget, C3D_FVec cameraUpVector, bool isLeftHanded);
///@}
///@name Quaternion Math

51
source/maths/mtx_lookat.c Normal file
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@ -0,0 +1,51 @@
#include <c3d/maths.h>
void Mtx_LookAt(C3D_Mtx* out, C3D_FVec cameraPosition, C3D_FVec cameraTarget, C3D_FVec cameraUpVector, bool isLeftHanded)
{
//Left-handed and Right-handed Look-At matrix functions are DirectX implementations.
//Left-handed: https://msdn.microsoft.com/en-us/library/windows/desktop/bb281710
//Right-handed: https://msdn.microsoft.com/en-us/library/windows/desktop/bb281711
C3D_FVec xaxis, yaxis, zaxis;
//Order of operations is crucial.
zaxis = FVec3_Normalize(FVec3_New(cameraPosition.x - cameraTarget.x, cameraPosition.y - cameraTarget.y, cameraPosition.z - cameraTarget.z));
xaxis = FVec3_Normalize(FVec3_Cross(cameraUpVector, zaxis));
yaxis = FVec3_Cross(zaxis, xaxis);
out->r[0].x = xaxis.x;
out->r[0].y = yaxis.x;
out->r[0].z = zaxis.x;
out->r[0].w = 0.0f;
if (isLeftHanded)
{
//In LH matrix, the Y is in Row 2 of 4 and the Z is in Row 3 of 4.
out->r[1].x = xaxis.y;
out->r[1].y = yaxis.y;
out->r[1].z = zaxis.y;
out->r[1].w = 0.0f;
out->r[2].x = xaxis.z;
out->r[2].y = yaxis.z;
out->r[2].z = zaxis.z;
out->r[2].w = 0.0f;
}
else
{
//In RH matrix, the Z is in Row 2 of 4, and the Y is in Row 3 of 4.
out->r[1].x = xaxis.z;
out->r[1].y = yaxis.z;
out->r[1].z = zaxis.z;
out->r[1].w = 0.0f;
out->r[2].x = xaxis.y;
out->r[2].y = yaxis.y;
out->r[2].z = zaxis.y;
out->r[2].w = 0.0f;
}
out->r[3].x = -FVec3_Dot(xaxis, cameraPosition);
out->r[3].y = -FVec3_Dot(yaxis, cameraPosition);
out->r[3].z = -FVec3_Dot(zaxis, cameraPosition);
out->r[3].w = 1.0f;
}