Comment Re:The first of many such comments... (Score 1) 563
from http://en.wikipedia.org/wiki/Direct3D_vs._OpenGL
Performance
Shortly after the establishment of both Direct3D and OpenGL as viable graphics libraries, Microsoft and SGI engaged in what has been called the "API Wars". Much of the argument revolved around which API offered superior performance. This question was relevant due to the very high cost of graphics accelerators during this time, which meant the consumer market was using software renderers implemented by Microsoft for both Direct3D and OpenGL.
Microsoft had marketed Direct3D as faster based on in-house performance comparisons of these two software libraries. The performance deficit was blamed on the rigorous specification and conformance required of OpenGL. This perception was changed at the 1996 SIGGRAPH (Special Interest Group on Computer Graphics) conference. At that time, SGI challenged Microsoft with their own optimized Windows software implementation of OpenGL called CosmoGL which in various demos matched or exceeded the performance of Direct3D. For SGI, this was a critical milestone as it showed that OpenGL's poor software rendering performance was due to Microsoft's inferior implementation, and not to design flaws in OpenGL itself.
Direct3D 9 and below have a particular disadvantage with regard to performance. Drawing a vertex array in Direct3D requires that the CPU switch to kernel-mode and call the graphics driver immediately. OpenGL, because its drivers have portions that run in user-mode, can perform marshalling activities to limit the number of kernel-mode switches and batch numerous calls in one kernel-mode switch. In effect, the number of vertex array drawing calls in a D3D application is limited to the speed of the CPU, as switching to kernel-mode is a fairly slow and CPU intensive operation.
Direct3D 10 allows portions of drivers to run in user-mode, thus allowing D3D10 applications to overcome this performance limitation.
Outside of this, Direct3D and OpenGL applications have no significant performance differences.
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In other words, OpenGL is not that bad performance-wise if you use a good implementation (aka not Microsofts). A good open source implementation is http://www.mesa3d.org/. Don't make me sic Carmack on you.
Performance
Shortly after the establishment of both Direct3D and OpenGL as viable graphics libraries, Microsoft and SGI engaged in what has been called the "API Wars". Much of the argument revolved around which API offered superior performance. This question was relevant due to the very high cost of graphics accelerators during this time, which meant the consumer market was using software renderers implemented by Microsoft for both Direct3D and OpenGL.
Microsoft had marketed Direct3D as faster based on in-house performance comparisons of these two software libraries. The performance deficit was blamed on the rigorous specification and conformance required of OpenGL. This perception was changed at the 1996 SIGGRAPH (Special Interest Group on Computer Graphics) conference. At that time, SGI challenged Microsoft with their own optimized Windows software implementation of OpenGL called CosmoGL which in various demos matched or exceeded the performance of Direct3D. For SGI, this was a critical milestone as it showed that OpenGL's poor software rendering performance was due to Microsoft's inferior implementation, and not to design flaws in OpenGL itself.
Direct3D 9 and below have a particular disadvantage with regard to performance. Drawing a vertex array in Direct3D requires that the CPU switch to kernel-mode and call the graphics driver immediately. OpenGL, because its drivers have portions that run in user-mode, can perform marshalling activities to limit the number of kernel-mode switches and batch numerous calls in one kernel-mode switch. In effect, the number of vertex array drawing calls in a D3D application is limited to the speed of the CPU, as switching to kernel-mode is a fairly slow and CPU intensive operation.
Direct3D 10 allows portions of drivers to run in user-mode, thus allowing D3D10 applications to overcome this performance limitation.
Outside of this, Direct3D and OpenGL applications have no significant performance differences.
-------
In other words, OpenGL is not that bad performance-wise if you use a good implementation (aka not Microsofts). A good open source implementation is http://www.mesa3d.org/. Don't make me sic Carmack on you.
