🔒 Locked 🎮 Unity

help: GL translation vs DirectX

Started by mercior Jan 3, 2010 at 9:22 PM 2 replies 800+ views

Original Post

Jan 3, 2010 at 9:22 PM

I'm trying to mimick this directx transform code in OpenGL:

Quote:
D3DXMATRIX tmp; D3DXMatrixTranslation(&matView, -x, -y, 0.0f); D3DXMatrixScaling(&tmp, hscale, vscale, 1.0f); D3DXMatrixMultiply(&matView, &matView, &tmp); D3DXMatrixRotationZ(&tmp, -rot); D3DXMatrixMultiply(&matView, &matView, &tmp); D3DXMatrixTranslation(&tmp, x+dx, y+dy, 0.0f); D3DXMatrixMultiply(&matView, &matView, &tmp);

using:

Quote:
glTranslatef(-x, -y, 0.0f); glScalef(hscale, vscale, 1.0f); glRotatef(-rot, 0, 0, 1); glTranslatef(x+dx, y+dy, 0.0f);

I've read up on the functions and this seems correct to me, but I'm new to GL and probably missing something! The GL code does not produce the same result. Can anybody help?

idinev

Jan 3, 2010 at 9:33 PM

Try reversing the order of ops.

mercior

Jan 3, 2010 at 11:57 PM

yup that worked :) not sure I get why though?

Yann L

Jan 4, 2010 at 12:26 AM

Quote:
Original post by mercior
yup that worked :) not sure I get why though?

Because OpenGL uses column-major matrices, while D3D uses row-major ones. Multiplication order needs to be flipped in order to get the same result.

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.