# Matrix and Quaternion mismatch

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Greetings! For long time now, I was parsing several 3D file formats, but there are still some questions open. In Half-Life .smd format by Valve there is something i can not understand: vertices are passed in following order: bone x y z nx ny nz u v yaw pitch roll What bothers me is that yaw pitch roll - that are rotation parameters in radians. When I say: (method 1) D3DXMatrixRotationX(&matrix_x, yaw); D3DXMatrixRotationY(&matrix_y, pitch); D3DXMatrixRotationZ(&matrix_z, roll); rotation_matrix = matrix_x * matrix_y * matrix_z; (method 2) everything works fine, but if I say: D3DXQuaternionRotationYawPitchRoll(&qrot, yaw, pitch, roll); D3DXMatrixRotationQuaternion(&rotation_matrix, &qrot); the two rotation matrices SOMETIMES (cca. 10% of all cases) differ. I MEAN REALLY DIFFER not just a smal floating precision fallof. I know one may say It could be in the order is it ypr, pyr, rpy etc... but it isn't! I tried all possible permutations/combinations but there are cases where the quaternion produced matrix differs a lot and in 90% of the cases it is the same as the first method. So the problem is, whenever i try to compute the rotation matrices with the quaternion method some of them get corrupted. I have used those quaternion functions also for Unreal and it works just superb. As for reverse engeneering I have also tried to export the ONE AND SAME MESH via smd exporter and a customized exporter that dumps corresponding quaternions that acctualy do work in unreal, but are different as I would compute them in method 2. All quaternions are practialy the same just some get corrupted and ONLY the corrupted ones differ in both exporters. Can anyone provide some help? I also tried like that: 1. compute by method 1 and get a quaternion out of it, 2. compute quaternion by method 2 and compare by step 1 3. if they differ there is something wrong Right at the moment I do not have any values to play with, but I will try to provide some that work and some that are corrupted. Thank you in advance!

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It looks like your code is basically doing the same thing (assuming the order is correct) but, just to be sure, have you tried using D3DMatrixRotationYawPitchRoll()? Like this:
D3DXMatrixRotationYawPitchRoll(&rotation_matrix1, yaw, pitch, roll);D3DXQuaternionRotationYawPitchRoll(&qrot, yaw, pitch, roll);D3DXMatrixRotationQuaternion(&rotation_matrix2, &qrot);
And then compare rotation_matrix1 and rotation_matrix2...

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I dare to believe mx*my*mz is not allways the same als D3DXMatrixRotationYawPitchRoll. I will trully try to find some time to find some values that mismatch and post them. But I am sure I have tried exactly the method you mentioned. I'm at work right now and it is hard to find time to seek for those values. I saw the math forum at gamedev and had to try it.

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Give an example of a set of YPR angles which reproduce the problem, and the quaternions produced by each approach.

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Perhaps yaw should be a rotation around the Y axis and pitch a rotation about the X axis? Also, I believe the order of multiplication should be M = roll * pitch * yaw. I'm pretty sure that's how D3DXxxxxxRotationYawPitchRoll interprets it. But in any case, I would use D3DXMatrixRotationYawPitchRoll instead of either method.

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