Forums Technical Discussion Read and keep the lowest pixel value from a sequence

Read and keep the lowest pixel value from a sequence

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Lancelot
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Hello everyone.

I have this Houdini scene that reads a motion vector sequence and compare 2 frames to read the lowest pixel value (in my example: lowest red). It work for the 2 frame, but I would like to do it for the entire sequence. I didn't find a way to keep the lowest value throughout the sequence.



At frame 63, the lowest value is at this frame (now: -1.0913). This is good.



At frame 64, the lowest value is at the previous frame (prev: -1.0913). Still good, it is the lowest value so far.



At frame 65, both value are higher than the lowest value we got so far and the result is the lowest value between the two frames (prev: -1.04709). This is now what I want. I would like RESULT to keep the lowest value so far (-1.0913).



But I have not find a way to do that. If someone have a solution to this, it would help me to automize the sequence analyze.

Thankyou.
Pierre Lalancette.
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Edited by Lancelot - Dec. 24, 2024 09:45:58

Attachments:
motion_vector.zip (499.8 KB)
problem_mv_02.jpg (15.0 KB)
problem_mv_03.jpg (12.9 KB)
problem_mv_04.jpg (12.5 KB)
problem_mv_01.jpg (504.7 KB)

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tamte
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You can use either Solver SOP to compare with previous frame

Or Foreach Block with feedback

Or you can also import your values to Chops using Geometry CHOP and get minimum of the resulting channel
Edited by tamte - Dec. 24, 2024 16:20:24
Tomas Slancik
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Lancelot
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I am already able to compare with the previous frame. It is to keep the highest or lowest value over the entire sequence that was the problem.

I am really not familiar with the foreach ways of Houdini, so I am more interested by your Geometry CHOP. I will look into that. Thanks.
Edited by Lancelot - Dec. 25, 2024 10:14:29
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tamte
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Lancelot
I am already able to compare with the previous frame. It is to keep the highest or lowest value over the entire sequence that was the problem.
Right, what I meant in Solver SOP by previous frame is that it will remember output of previous frame
So every frame the previous frame can be the minimum of all previous frames etc.

I can provide examples of mentioned methods, when I get to Houdini
Tomas Slancik
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Lancelot
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Indeed, I am curious on how to do that because I miss the way to keep that low value from one frame to the next. The actual frame value always overwrite what I try to keep. I just don't know the proper way to do it.

Pierre.
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tamte
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here are all mentioned methods, also adding COP method to compute per frame min/max values and altered SOP method to actually sample centers of the pixels rather than interpolating at corners
Edited by tamte - yesterday 22:09:40

Attachments:
motion_vector_mod.hipnc (214.0 KB)

Tomas Slancik
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Lancelot
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Thankyou Tamte.
I'll be analyzing this file as soon as I can.

Pierre.
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