On Tue, Mar 23, 2021 at 5:00 AM Daniel Playfair Cal < daniel.playfair....@gmail.com> wrote:
> What exactly is your definition of fisheye? > Take look at source code. I do not see how your definition matches one in source code. > > The definition I'm working with is the equidistant fisheye projection as > described here: https://wiki.panotools.org/Fisheye_Projection, i.e. r = f > * theta > > That mapping works for any theta, and you can have a circular image with a > field of view of up to 360 degrees before anything is repeated and the > inverse mapping is ambiguous. Hence my assumption that a rectangular output > image with a 180 horizontal/vertical field of view should still contain > areas near the corners where theta > 90 (because the diagonal FoV is > > 180), and these should still be mapped from such an image to a > equirectangular projection. > > Do you prefer for some reason to limit the fisheye projection to 180 > degrees on any axis, i.e. have the constraint that theta <= 90? If that's > the case I could patch xyz_to_fisheye and fisheye_to_xyz so that such areas > are marked as invisible? That causes your example filtergraph to work as > before. > > On Tue, Mar 23, 2021 at 3:46 AM Paul B Mahol <one...@gmail.com> wrote: > >> >> >> On Mon, Mar 22, 2021 at 1:35 PM Daniel Playfair Cal < >> daniel.playfair....@gmail.com> wrote: >> >>> > I disagree, if I use 180 hfov and 180 vfov it should not have extra >>> areas but only half of previous input. >>> >>> Not sure I follow - the ih_fov and vh_fov refer to the input (i.e. the >>> fisheye image). If you wanted to restrict the FoV of the output, surely the >>> way to do that would be to implement and use the FoV settings for the >>> equirectangular projection?. It doesn't seem right that the code for the >>> input projection is responsible for deciding what appears in the output. My >>> understanding was that the FoV settings simply describe the focal length of >>> the input or output camera so that points in the images can me mapped >>> to/from 3d coordinates. >>> >>> >> Take any equirectangular input and convert it to fisheye and than back to >> equirectangular. >> Or just take pure fisheye input with 180 h & v fov and convert it to >> equirectangular. There is plenty of such video content on esa website. >> >> To give you an idea of what I am trying to fix, here is an example input: >>> https://photos.app.goo.gl/o51NfY6aqWn3unPG6 >>> This is a 1920x1440 image taken on a GoPro Hero 5 black with the 4:3 >>> Wide FoV setting and stabilisation disabled. >>> >>> >> That is flat take of something else. Not real fisheye input. >> >> >>> The following filtergraph demonstrates the issues: >>> 'v360=input=fisheye:ih_fov=116.66:iv_fov=87.50:output=flat:d_fov=145.8' >>> 1. the dfov_from_hfov issue is worked around by the use of ih_fov and >>> iv_fov instead of id_fov, although you can try with id_fov=145.8 to see >>> that problem too >>> 2. by default the output has double the aspect ratio of the input, even >>> though the fisheye -> rectilinear transformation doesn't change the aspect >>> ratio (assuming the entire input image is included as it is in this example) >>> 3. much of the input is not visible in the output even though there is >>> a mapping between the chosen projections (changed in the visibility test >>> patch) >>> >>> 3 in particular I don't think can be solved by changing the settings - >>> the input field of view needs to match the FoV of the input camera, >>> otherwise the mapping is wrong. But it seems there is no other way to >>> include the entire input from a fisheye image. >>> >>> On Mon, Mar 22, 2021 at 5:59 PM Paul B Mahol <one...@gmail.com> wrote: >>> >>>> >>>> >>>> On Mon, Mar 22, 2021 at 5:09 AM Daniel Playfair Cal < >>>> daniel.playfair....@gmail.com> wrote: >>>> >>>>> I've tried that filtergraph and a few other similar ones and I'm not >>>>> sure what you mean - what exactly is the regression? >>>>> >>>>> I tried it on this image with an equirectangular projection: >>>>> https://wiki.panotools.org/images/0/01/Big_ben_equirectangular.jpg >>>>> >>>>> The only difference I can see is that there are less unmapped areas in >>>>> the output with the patches, because the final mapping from the output >>>>> equirectangular image to the intermediate fisheye image no longer fails to >>>>> map some areas which are present in the fisheye image. I would describe >>>>> this as an improvement? >>>>> >>>> >>>> I disagree, if I use 180 hfov and 180 vfov it should not have extra >>>> areas but only half of previous input. >>>> >>>> >>>>> >>>>> On Mon, Mar 22, 2021 at 3:30 AM Paul B Mahol <one...@gmail.com> wrote: >>>>> >>>>>> Sorry, but I cannot apply this set as is, It makes at least one >>>>>> serious regression. >>>>>> >>>>>> For example try this filtergraph: >>>>>> >>>>>> >>>>>> v360=input=e:output=fisheye:h_fov=180:v_fov=180,v360=input=fisheye:output=e:ih_fov=180:iv_fov=180 >>>>>> >>>>>> On Sun, Mar 21, 2021 at 1:45 PM Daniel Playfair Cal < >>>>>> daniel.playfair....@gmail.com> wrote: >>>>>> >>>>>>> This changes the iflat_range and flat_range values for the fisheye >>>>>>> projection to match their meaning for the flat/rectilinear >>>>>>> projection. >>>>>>> That is, the range is between the two x or two y coordinates of the >>>>>>> outermost points above/below or left/right of the center, in the >>>>>>> flat/rectilinear projection. >>>>>>> >>>>>>> Signed-off-by: Daniel Playfair Cal <daniel.playfair....@gmail.com> >>>>>>> --- >>>>>>> libavfilter/vf_v360.c | 19 +++++++++---------- >>>>>>> 1 file changed, 9 insertions(+), 10 deletions(-) >>>>>>> >>>>>>> diff --git a/libavfilter/vf_v360.c b/libavfilter/vf_v360.c >>>>>>> index 68bb2f7b0f..3158451963 100644 >>>>>>> --- a/libavfilter/vf_v360.c >>>>>>> +++ b/libavfilter/vf_v360.c >>>>>>> @@ -2807,9 +2807,8 @@ static int prepare_fisheye_out(AVFilterContext >>>>>>> *ctx) >>>>>>> { >>>>>>> V360Context *s = ctx->priv; >>>>>>> >>>>>>> - s->flat_range[0] = s->h_fov / 180.f; >>>>>>> - s->flat_range[1] = s->v_fov / 180.f; >>>>>>> - >>>>>>> + s->flat_range[0] = 0.5f * s->h_fov * M_PI / 180.f; >>>>>>> + s->flat_range[1] = 0.5f * s->v_fov * M_PI / 180.f; >>>>>>> return 0; >>>>>>> } >>>>>>> >>>>>>> @@ -2827,8 +2826,8 @@ static int fisheye_to_xyz(const V360Context *s, >>>>>>> int i, int j, int width, int height, >>>>>>> float *vec) >>>>>>> { >>>>>>> - const float uf = s->flat_range[0] * ((2.f * i) / width - 1.f); >>>>>>> - const float vf = s->flat_range[1] * ((2.f * j + 1.f) / height - >>>>>>> 1.f); >>>>>>> + const float uf = 2.f * s->flat_range[0] / M_PI * ((2.f * i) / >>>>>>> width - 1.f); >>>>>>> + const float vf = 2.f * s->flat_range[1] / M_PI * ((2.f * j + >>>>>>> 1.f) / height - 1.f); >>>>>>> >>>>>>> const float phi = atan2f(vf, uf); >>>>>>> const float theta = M_PI_2 * (1.f - hypotf(uf, vf)); >>>>>>> @@ -2858,8 +2857,8 @@ static int prepare_fisheye_in(AVFilterContext >>>>>>> *ctx) >>>>>>> { >>>>>>> V360Context *s = ctx->priv; >>>>>>> >>>>>>> - s->iflat_range[0] = s->ih_fov / 180.f; >>>>>>> - s->iflat_range[1] = s->iv_fov / 180.f; >>>>>>> + s->iflat_range[0] = 0.5f * s->ih_fov * M_PI / 180.f; >>>>>>> + s->iflat_range[1] = 0.5f * s->iv_fov * M_PI / 180.f; >>>>>>> >>>>>>> return 0; >>>>>>> } >>>>>>> @@ -2882,10 +2881,10 @@ static int xyz_to_fisheye(const V360Context >>>>>>> *s, >>>>>>> { >>>>>>> const float h = hypotf(vec[0], vec[1]); >>>>>>> const float lh = h > 0.f ? h : 1.f; >>>>>>> - const float phi = atan2f(h, vec[2]) / M_PI; >>>>>>> + const float phi = atan2f(h, vec[2]); >>>>>>> >>>>>>> - float uf = vec[0] / lh * phi / s->iflat_range[0]; >>>>>>> - float vf = vec[1] / lh * phi / s->iflat_range[1]; >>>>>>> + float uf = 0.5f * vec[0] / lh * phi / s->iflat_range[0]; >>>>>>> + float vf = 0.5f * vec[1] / lh * phi / s->iflat_range[1]; >>>>>>> >>>>>>> const int visible = -0.5f < uf && uf < 0.5f && -0.5f < vf && vf >>>>>>> < 0.5f; >>>>>>> int ui, vi; >>>>>>> -- >>>>>>> 2.31.0 >>>>>>> >>>>>>> _______________________________________________ >>>>>>> ffmpeg-devel mailing list >>>>>>> ffmpeg-devel@ffmpeg.org >>>>>>> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel >>>>>>> >>>>>>> To unsubscribe, visit link above, or email >>>>>>> ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". >>>>>> >>>>>> _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
