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ShawMishrak

OpenGL Direct3D and OpenGL

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ShawMishrak    146
For a project, I am creating identical renderer classes for both OpenGL and Direct3D8. The main program should not know what renderer its using; only worry about loading either "d3drend.dll" or "glrend.dll". I''ve noticed that the Direct3D and OpenGL coordinate systems differ a bit (inverted Z-axis). I have tried making all the Z values negative on the OpenGL version, but the perspective view (gluPerspective) still differs. What is required to get Direct3D and OpenGL to display the same results? Thanks in advance.

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Rocket05    152
the difference between OpenGL and Direct3D8's coordinate systems is that of left handed and right handed system. Basically, it just means which direction the positive z axis points, towards or away from the viewer. OpenGL defaults to left handed system, Direct3D to a right handed. Although im sure you can get OpenGL to switch, I think its easer to get Direct3D to switch. All you have to do is when setting the projection matrix for D3D, use the lefthanded version of function (I believe everything is the same except for a LH at the end of the functions name). Look it up on MSDN for more info.

zoning out

"If people were perfect, what would the point of life be?" -- meself

Edited by - Rocket05 on November 8, 2001 7:06:08 PM

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ShawMishrak    146
Thanks, that solved the inverted Z-axis problem without resorting to making all of my Z values negative when I build the vertex buffers. My only other question now is about what appears to be the aspect ratio of the perspective matrix. With a 90 degree FOV and ScreenWidth/ScreenHeight for the aspect ratio, the OpenGL viewport seems to either be closer to the object or have a closer zoom on the object. The object in Direct3D takes about a third of the screen space as the same object in OpenGL. Can anyone give any advice on how to possibly fix this? Thanks in advance.

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