Question about homo_warping about mvsnet_pytorch HOT 15 OPEN

No, translation doesn't need depth values. Originally it is a matrix multiplication of 4x4 (projection matrix) times 4x1 (3d coordinate, homogeneous) as follows:

[R T] [xd]
[0 1] [yd]
      [d]
      [1]

= [R][xd] + [T]
     [yd]
     [d]

So if you do the multiplication, the parts with d inside is only multiplied with R.

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@kwea123 In the Homo warming function, the normalization result after coordinate transformation may not be between - 1 and 1. How do you understand this? I look forward to your reply, thank you.

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If it's not between -1 and 1 it means that pixel is warped outside of the image, in that case that pixel has value 0 (all black) which is specified by padding_mode='zeros'

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@JiangQi715 See the usage of grid_sample

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@kwea123 OK, I see what you mean. Now I have a problem: all the pixels are warped out of the image. What may be the problem? Is the previous matrix operation wrong (resulting in a warp error)?

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@whubaichuan 您好，这个grid_sample我用起来了。是在这个grid_sample之前遇到了一个问题：homo_warming函数中，像素坐标变换（旋转平移）后，x和y坐标变大了（超过了宽度W和高度H），使用这个代码的归一化方法后，导致grid全部在[-1,1]之外。请问可能是哪里出了问题？是不是前面的矩阵运算出错了（导致坐标变换错误）？还是这个归一化方法不适用呢？十分谢谢。

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@whubaichuan 您好，这个grid_sample我用起来了。是在这个grid_sample之前遇到了一个问题：homo_warming函数中，像素坐标变换（旋转平移）后，x和y坐标变大了（超过了宽度W和高度H），使用这个代码的归一化方法后，导致grid全部在[-1,1]之外。请问可能是哪里出了问题？是不是前面的矩阵运算出错了（导致坐标变换错误）？还是这个归一化方法不适用呢？十分谢谢。

代码在MVSNet_pytorch/models/module.py的117-123行

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你用的是DTU dataset?這是不可能的，這個代碼我確認過了是正確的，不會全部在[-1, 1]之外的。
還是你用的是別的dataset?

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那可能是我的DTU数据集预处理部分出了一些问题，我自己再检查一下。再次感谢您。

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@JiangQi715 是不是用到了torch.meshgrid？。注意其和np.meshgrid和tf.meshgrid的区别

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@JiangQi715 是不是用到了torch.meshgrid？。注意其和np.meshgrid和tf.meshgrid的区别

是的，用到了，我查一下。谢谢您。

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Hi CoolCats[0]
Nice to see your discussions above, as I am new to this domain and your discussions really help! Regarding the homo_warping function(), I do have one more concern and hoping to learn from your ideas on this. Any comments are appreciated!
In

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@czha5168 In fact, the code "with torch.no_grad()" is redundant. Cause that the grid will not pass the grad back. So if you delete the code "with torch.no_grad()", it's no different.

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@czha5168 In fact, the code "with torch.no_grad()" is redundant. Cause that the grid will not pass the grad back. So if you delete the code "with torch.no_grad()", it's no different.

Hi Baichuan! Thanks so much for your reply!

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@JiangQi715 是不是用到了torch.meshgrid？。注意其和np.meshgrid和tf.meshgrid的区别

Hi,recently I have a problemin homo_warp, If there is occlusion in the sampling place, the wrong place will be sampled, have you considered this problem? can you tell me how to solve？

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