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Bug fix and improvement to FBX camera field-of-view during import. #5175

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merged 5 commits into from
Jul 23, 2023
Merged

Bug fix and improvement to FBX camera field-of-view during import. #5175

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aab3c80
Correct from full FOV to assimp half-fov in camera. Compute from film…
Jun 15, 2023
c7afea3
Merge branch 'assimp:master' into sfjohnston_mods
sfjohnston Jul 10, 2023
64e0ba2
Merge branch 'master' into sfjohnston_mods
kimkulling Jul 20, 2023
3ec8a36
Merge branch 'assimp:master' into sfjohnston_mods
sfjohnston Jul 23, 2023
dd40b0c
Changed #define FBX_FOV_UNKNOWN to const float kFovUnknown
sfjohnston Jul 23, 2023
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26 changes: 21 additions & 5 deletions code/AssetLib/FBX/FBXConverter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -93,6 +93,8 @@ FBXConverter::FBXConverter(aiScene *out, const Document &doc, bool removeEmptyBo
mSceneOut(out),
doc(doc),
mRemoveEmptyBones(removeEmptyBones) {


// animations need to be converted first since this will
// populate the node_anim_chain_bits map, which is needed
// to determine which nodes need to be generated.
Expand Down Expand Up @@ -427,12 +429,26 @@ void FBXConverter::ConvertCamera(const Camera &cam, const std::string &orig_name
out_camera->mLookAt = aiVector3D(1.0f, 0.0f, 0.0f);
out_camera->mUp = aiVector3D(0.0f, 1.0f, 0.0f);

out_camera->mHorizontalFOV = AI_DEG_TO_RAD(cam.FieldOfView());

out_camera->mClipPlaneNear = cam.NearPlane();
out_camera->mClipPlaneFar = cam.FarPlane();
// NOTE: Some software (maya) does not put FieldOfView in FBX, so we compute
// mHorizontalFOV from FocalLength and FilmWidth with unit conversion.

// TODO: This is not a complete solution for how FBX cameras can be stored.
// TODO: Incorporate non-square pixel aspect ratio.
// TODO: FBX aperture mode might be storing vertical FOV in need of conversion with aspect ratio.

float fov_deg = cam.FieldOfView();
// If FOV not specified in file, compute using FilmWidth and FocalLength.
if (fov_deg == FBX_FOV_UNKNOWN) {
float film_width_inches = cam.FilmWidth();
float focal_length_mm = cam.FocalLength();
ASSIMP_LOG_VERBOSE_DEBUG("FBX FOV unspecified. Computing from FilmWidth (", film_width_inches, "inches) and FocalLength (", focal_length_mm, "mm).");
double half_fov_rad = std::atan2(film_width_inches * 25.4 * 0.5, focal_length_mm);
out_camera->mHorizontalFOV = half_fov_rad;
} else {
// FBX fov is full-view degrees. We want half-view radians.
out_camera->mHorizontalFOV = AI_DEG_TO_RAD(fov_deg) * 0.5;
}

out_camera->mHorizontalFOV = AI_DEG_TO_RAD(cam.FieldOfView());
out_camera->mClipPlaneNear = cam.NearPlane();
out_camera->mClipPlaneFar = cam.FarPlane();
}
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6 changes: 5 additions & 1 deletion code/AssetLib/FBX/FBXDocument.h
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Expand Up @@ -55,9 +55,13 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#define _AI_CONCAT(a,b) a ## b
#define AI_CONCAT(a,b) _AI_CONCAT(a,b)

/* Use an 'illegal' default FOV value to detect if the FBX camera has set the FOV. */
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Please use // style comments. This will make it much easier to put bigger blocks into comments.

#define FBX_FOV_UNKNOWN -1.0f
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namespace Assimp {
namespace FBX {


class Parser;
class Object;
struct ImportSettings;
Expand Down Expand Up @@ -247,7 +251,7 @@ class Camera : public NodeAttribute {
fbx_simple_property(FilmAspectRatio, float, 1.0f)
fbx_simple_property(ApertureMode, int, 0)

fbx_simple_property(FieldOfView, float, 1.0f)
fbx_simple_property(FieldOfView, float, FBX_FOV_UNKNOWN)
fbx_simple_property(FocalLength, float, 1.0f)
};

Expand Down