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Hi Aaron:
This is a somewhat "official" response to your question ... (grin) ... or at least a response from a person on the Autodesk Inventor team who actually works with and writes the code that connects to Direct3D and OpenGL ... (grin)
I have posted replies to similar questions before and I will summarize again, because your subject raises the question directly.
There is one huge difference between Direct3D and OpenGL regarding graphics drivers. Direct3D API usage and functionality support is tested by Microsoft as part of the Windows Hardware Quality Lab (WHQL) graphics driver testing and certification process. OpenGL usage has never been and is not now part of the WHQL certification.
We are using the Direct3D API in a standard way, using the functionality in the Direct3D spec which is tested by WHQL. Therefore, the normal assumption which should be reasonable is that if your graphics driver is WHQL certified, the chances are very good that Autodesk Inventor R11 will work using Direct3D.
This is not true for OpenGL. The reason we have such an extensive Hardware Library of graphics card certifications for OpenGL is because the OpenGL community has no equivalent conformance and certification process apart from accepting the word of the graphics HW vendor that the driver works. Based on our many years of experience, this is something we cannot do so we must spend a significant amount of effort testing and certifying OpenGL graphics drivers ourselves.
This is our first release using Direct3D. While we occassionaly encounter mistakes on our part in terms of Direct3D API usage, Direct3D itself seems to work fine. The opposite is true of OpenGL. We have been using OpenGL for many years and have very few new changes in our OpenGL API usage. In spite of this, we continue to encounter new graphics drivers from HW vendors that fail our testing and certification, even though our code may not have changed at all in terms of where the problems appear.
If OpenGL works fine for you, that is great and you can use it. On the other hand, while we have had over ten years of using OpenGL, which should be time for the OpenGL HW vendors to "get it right" (grin), they haven't been able to do that, as I mention above. We are no longer willing to be so tolerant of crash-to-desktop situations that are _not_ caused by our code but are caused by bad OpenGL grapihcs drivers from graphics HW vendors. Given that Microsoft has the WHQL testing and certification program, we are now working with Direct3D under the assumption that we will not have the same level of catastrophic failures we have seen all too frequently with OpenGL graphics drivers.
As I mentioned above, this is our first release using Direct3D and given that we have had over ten years to make our usage of the OpenGL API "correct", we expect that we will have a few Direct3D API usage items to sort out and may not have found every possible problem in this initial release. The hope is that with continued use of Direct3D, we will solve any outstanding Direct3D API usage items that we may have and we will provide an experience using Inventor across all graphics HW that is reliable, conformant to the "correct" display, has optimal performance, and allows us to use advanced 3D graphics HW features and functionality in a way that you can benefit from as opposed to tentatively trying out new features to see if the graphics driver will crash under you, which has been the all-too-frequent experience with OpenGL graphics drivers for over ten years.
I hope this helps provide some background for you.
Thanks,
Norbert
Norbert Jeske
Graphics and Visualization Technology Lead
Autodesk, Inc.
This is a somewhat "official" response to your question ... (grin) ... or at least a response from a person on the Autodesk Inventor team who actually works with and writes the code that connects to Direct3D and OpenGL ... (grin)
I have posted replies to similar questions before and I will summarize again, because your subject raises the question directly.
There is one huge difference between Direct3D and OpenGL regarding graphics drivers. Direct3D API usage and functionality support is tested by Microsoft as part of the Windows Hardware Quality Lab (WHQL) graphics driver testing and certification process. OpenGL usage has never been and is not now part of the WHQL certification.
We are using the Direct3D API in a standard way, using the functionality in the Direct3D spec which is tested by WHQL. Therefore, the normal assumption which should be reasonable is that if your graphics driver is WHQL certified, the chances are very good that Autodesk Inventor R11 will work using Direct3D.
This is not true for OpenGL. The reason we have such an extensive Hardware Library of graphics card certifications for OpenGL is because the OpenGL community has no equivalent conformance and certification process apart from accepting the word of the graphics HW vendor that the driver works. Based on our many years of experience, this is something we cannot do so we must spend a significant amount of effort testing and certifying OpenGL graphics drivers ourselves.
This is our first release using Direct3D. While we occassionaly encounter mistakes on our part in terms of Direct3D API usage, Direct3D itself seems to work fine. The opposite is true of OpenGL. We have been using OpenGL for many years and have very few new changes in our OpenGL API usage. In spite of this, we continue to encounter new graphics drivers from HW vendors that fail our testing and certification, even though our code may not have changed at all in terms of where the problems appear.
If OpenGL works fine for you, that is great and you can use it. On the other hand, while we have had over ten years of using OpenGL, which should be time for the OpenGL HW vendors to "get it right" (grin), they haven't been able to do that, as I mention above. We are no longer willing to be so tolerant of crash-to-desktop situations that are _not_ caused by our code but are caused by bad OpenGL grapihcs drivers from graphics HW vendors. Given that Microsoft has the WHQL testing and certification program, we are now working with Direct3D under the assumption that we will not have the same level of catastrophic failures we have seen all too frequently with OpenGL graphics drivers.
As I mentioned above, this is our first release using Direct3D and given that we have had over ten years to make our usage of the OpenGL API "correct", we expect that we will have a few Direct3D API usage items to sort out and may not have found every possible problem in this initial release. The hope is that with continued use of Direct3D, we will solve any outstanding Direct3D API usage items that we may have and we will provide an experience using Inventor across all graphics HW that is reliable, conformant to the "correct" display, has optimal performance, and allows us to use advanced 3D graphics HW features and functionality in a way that you can benefit from as opposed to tentatively trying out new features to see if the graphics driver will crash under you, which has been the all-too-frequent experience with OpenGL graphics drivers for over ten years.
I hope this helps provide some background for you.
Thanks,
Norbert
Norbert Jeske
Graphics and Visualization Technology Lead
Autodesk, Inc.
Inventor R11 is using DirectX 9.0c. We build R11 using the October 2005 DirectX SDK. This also means we use version 27 of the D3DX utility library that comes with the October 2005 SDK.
You are correct that the Quadro4 series of nVidia HW does not fully support all the features of the DirectX 9.0 spec. Fortunately for us, the only serious feature we need that is missing, support for clipping planes, can be accomplished by using the Direct3D SW Vertex Processing path so with this generation of nVidia HW, we use SW Vertex Processing.
Please note that the missing support for clipping planes is also "missing" on the OpenGL side; the nVidia OpenGL driver will just accomidate the need by a couple of different options, one being switching to a SW Vertex Processing path when clipping planes are in use.
Thanks,
Norbert
Norbert Jeske
Graphics and Visualization Technology Lead
Autodesk, Inc.
You are correct that the Quadro4 series of nVidia HW does not fully support all the features of the DirectX 9.0 spec. Fortunately for us, the only serious feature we need that is missing, support for clipping planes, can be accomplished by using the Direct3D SW Vertex Processing path so with this generation of nVidia HW, we use SW Vertex Processing.
Please note that the missing support for clipping planes is also "missing" on the OpenGL side; the nVidia OpenGL driver will just accomidate the need by a couple of different options, one being switching to a SW Vertex Processing path when clipping planes are in use.
Thanks,
Norbert
Norbert Jeske
Graphics and Visualization Technology Lead
Autodesk, Inc.
Hi Aaron:
Glen has already answered your question but I wanted to mention that your question unwittingly illustrates the reason for my _long_ (grin) explanation. The reason you see an "error" from Inventor R11 is because you have checked the checkbox:
"Warn me if I'm not using a recommended graphics driver"
under Tools => Application Options => Hardware. This is not checked by default.
Having this checked is a _good_ idea when using OpenGL, for all the reasons I mentioned earlier. The assumption when using OpenGL is that the graphics driver is "bad" _unless_ we have certified it in our Graphics Lab.
The _opposite_ assumption seems to be the case with Direct3D. A WHQL certified Direct3D graphics driver can in general be considered "good" so having this checkbox checked when using Direct3D is a bit redundant. In the case of Direct3D, this "error" simply indicates that our Graphics Lab has not yet managed to test your graphics driver with Direct3D, which if you are using a WHQL certified graphics driver, is not as critical for you as it would be if you were using OpenGL.
Thanks,
Norbert
Norbert Jeske
Graphics and Visualization Technology Lead
Autodesk, Inc.
Glen has already answered your question but I wanted to mention that your question unwittingly illustrates the reason for my _long_ (grin) explanation. The reason you see an "error" from Inventor R11 is because you have checked the checkbox:
"Warn me if I'm not using a recommended graphics driver"
under Tools => Application Options => Hardware. This is not checked by default.
Having this checked is a _good_ idea when using OpenGL, for all the reasons I mentioned earlier. The assumption when using OpenGL is that the graphics driver is "bad" _unless_ we have certified it in our Graphics Lab.
The _opposite_ assumption seems to be the case with Direct3D. A WHQL certified Direct3D graphics driver can in general be considered "good" so having this checkbox checked when using Direct3D is a bit redundant. In the case of Direct3D, this "error" simply indicates that our Graphics Lab has not yet managed to test your graphics driver with Direct3D, which if you are using a WHQL certified graphics driver, is not as critical for you as it would be if you were using OpenGL.
Thanks,
Norbert
Norbert Jeske
Graphics and Visualization Technology Lead
Autodesk, Inc.
Hi Jonathan:
We need to understand what you mean by "superior performance" (grin). In my previous long (grin) explanation, I mentioned four characteristics: reliable, conformant to the "correct" display, optimal performance, and use of advanced 3D graphics HW features and functionality.
Note that perfomance is the third characteristic; if your OpenGL graphics driver causes your application to crash-to-desktop or gives you an "incorrect" display, then being able to draw billions of triangles per second is a bit meaningless, no?
The problem for OpenGL is that the first two characteristics are such an issue, especially if you don't use a "workstation" graphics card. In fact, even with a "workstation" (e.g. CAD) graphics card, the magnificent failure of OpenGL to live up to its Marketing claim of being a professional level 3D graphics API is illustrated by the fact that if you go to a typical graphics HW vendor web page to download a "workstation" graphics driver, you will typically encounter a list (over 70 in one case) of the applications that have "certified" the "workstation" graphics driver. An obvious question that comes to mind is why this is necessary if OpenGL is a "professional" level 3D API?
This is not to say that Direct3D "just works" (grin); rather the situation with Direct3D is that Microsoft enforces a level of reliablity and conformance to the "correct" display result via WHQL ... and this applies to _all_ graphiics HW, whether it is "workstation" or "consumer" level graphics HW. Essentially, using Direct3D and the exsistence of WHQL allows us to focus on the latter two characteristics, performance and advanced functionality.
So ... back to your question (grin) ... moving forward, we now have much greater flexibilty to focus on 3D graphics HW performance optimizations and the use of advanced features and functionality ... and this applies to _all_ graphics HW, not just the best CAD graphics card you can afford. From our standpoint, we would like the only differentiator to be performance; meaning the reason for a newer or more expensive graphics card is because it is faster or does have advanced features and functionality that allows it to generate the "correct" display faster than an older or less expensive graphics card. From the standpoint of a SW developer, this goal is much easier to realize across a wide range of graphics HW if using Direct3D than if using OpenGL.
I hope this helps you understand the situation.
Thanks,
Norbert
Norbert Jeske
Graphics and Visualization Technology Lead
Autodesk, Inc.
We need to understand what you mean by "superior performance" (grin). In my previous long (grin) explanation, I mentioned four characteristics: reliable, conformant to the "correct" display, optimal performance, and use of advanced 3D graphics HW features and functionality.
Note that perfomance is the third characteristic; if your OpenGL graphics driver causes your application to crash-to-desktop or gives you an "incorrect" display, then being able to draw billions of triangles per second is a bit meaningless, no?
The problem for OpenGL is that the first two characteristics are such an issue, especially if you don't use a "workstation" graphics card. In fact, even with a "workstation" (e.g. CAD) graphics card, the magnificent failure of OpenGL to live up to its Marketing claim of being a professional level 3D graphics API is illustrated by the fact that if you go to a typical graphics HW vendor web page to download a "workstation" graphics driver, you will typically encounter a list (over 70 in one case) of the applications that have "certified" the "workstation" graphics driver. An obvious question that comes to mind is why this is necessary if OpenGL is a "professional" level 3D API?
This is not to say that Direct3D "just works" (grin); rather the situation with Direct3D is that Microsoft enforces a level of reliablity and conformance to the "correct" display result via WHQL ... and this applies to _all_ graphiics HW, whether it is "workstation" or "consumer" level graphics HW. Essentially, using Direct3D and the exsistence of WHQL allows us to focus on the latter two characteristics, performance and advanced functionality.
So ... back to your question (grin) ... moving forward, we now have much greater flexibilty to focus on 3D graphics HW performance optimizations and the use of advanced features and functionality ... and this applies to _all_ graphics HW, not just the best CAD graphics card you can afford. From our standpoint, we would like the only differentiator to be performance; meaning the reason for a newer or more expensive graphics card is because it is faster or does have advanced features and functionality that allows it to generate the "correct" display faster than an older or less expensive graphics card. From the standpoint of a SW developer, this goal is much easier to realize across a wide range of graphics HW if using Direct3D than if using OpenGL.
I hope this helps you understand the situation.
Thanks,
Norbert
Norbert Jeske
Graphics and Visualization Technology Lead
Autodesk, Inc.
Hi Rick:
It is not quite that simple as "Yes or No" ... at least not right now.
If comparing Direct3D on a gaming card versus a CAD card, check the specs from the graphics HW vendor. Since you are using the same API in this case, the relative performance and graphics memory specified for the cards gives you a measure of how they compare.
If you are comparing Direct3D versus OpenGL, then you need to remember that you use OpenGL on the gaming card at your own risk because the graphics HW vendors will not support your use of OpenGL for CAD on a gaming card (wait ..., isn't OpenGL a "standard"??? (grin)).
OpenGL gives much greater latitude to the graphics HW vendor to "correct" any significant application performance issues by collecting and reorganizing data received from the application in the graphics driver. In this way, an application can be "improved" by a graphics HW vendor, simply by special handling for the OpenGL API calls. This is why in your OpenGL tabs for your Display Properties, you can choose the Application Profile. This is telling your OpenGL graphics driver to "adjust" itself to expect the chosen application to be running and to "interpret" OpenGL API calls according to any history and experience that the OpenGL vendor has for this application.
Direct3D does not give this same degree of latitude to the graphics driver, instead requiring the _application_ to implement its usage of Direct3D with some realities of 3D graphics HW in mind. This is not a _bad_ thing (grin); there is only so much "improvement" that a graphcs driver can do on its own ... and these "improvements" can lead to serious problems with reliability and conformance ... which we are all too familar with in OpenGL.
At the moment, we benefit from some of the OpenGL graphics driver "improvements" and suffer from others; this is the reason for our extensive set of work-around bits for use with OpenGL. The benefits seem to all be performance benefits and the negative aspects are mostly reliability and conformance problems.
So, if you are interested in comparing Direct3D versus OpenGL in R11 right now, there are certain OpenGL graphics drivers that might "improve" our API usage significantly and you will see better performance with OpenGL, provided you do not have problems with reliabilty and conformance.
If you are thinking about the future, stay tuned ... (grin) ... as I just mentioned, Direct3D expects the _application_ to improve itself for better performance, not rely on the graphics driver to do this for it and we are acting accordingly. Given that Direct3D works the same on gaming cards as on CAD cards, the improvements we make will apply across all graphics HW for Direct3D.
Thanks,
Norbert
Norbert Jeske
Graphics and Visualization Technology Lead
Autodesk, Inc.
It is not quite that simple as "Yes or No" ... at least not right now.
If comparing Direct3D on a gaming card versus a CAD card, check the specs from the graphics HW vendor. Since you are using the same API in this case, the relative performance and graphics memory specified for the cards gives you a measure of how they compare.
If you are comparing Direct3D versus OpenGL, then you need to remember that you use OpenGL on the gaming card at your own risk because the graphics HW vendors will not support your use of OpenGL for CAD on a gaming card (wait ..., isn't OpenGL a "standard"??? (grin)).
OpenGL gives much greater latitude to the graphics HW vendor to "correct" any significant application performance issues by collecting and reorganizing data received from the application in the graphics driver. In this way, an application can be "improved" by a graphics HW vendor, simply by special handling for the OpenGL API calls. This is why in your OpenGL tabs for your Display Properties, you can choose the Application Profile. This is telling your OpenGL graphics driver to "adjust" itself to expect the chosen application to be running and to "interpret" OpenGL API calls according to any history and experience that the OpenGL vendor has for this application.
Direct3D does not give this same degree of latitude to the graphics driver, instead requiring the _application_ to implement its usage of Direct3D with some realities of 3D graphics HW in mind. This is not a _bad_ thing (grin); there is only so much "improvement" that a graphcs driver can do on its own ... and these "improvements" can lead to serious problems with reliability and conformance ... which we are all too familar with in OpenGL.
At the moment, we benefit from some of the OpenGL graphics driver "improvements" and suffer from others; this is the reason for our extensive set of work-around bits for use with OpenGL. The benefits seem to all be performance benefits and the negative aspects are mostly reliability and conformance problems.
So, if you are interested in comparing Direct3D versus OpenGL in R11 right now, there are certain OpenGL graphics drivers that might "improve" our API usage significantly and you will see better performance with OpenGL, provided you do not have problems with reliabilty and conformance.
If you are thinking about the future, stay tuned ... (grin) ... as I just mentioned, Direct3D expects the _application_ to improve itself for better performance, not rely on the graphics driver to do this for it and we are acting accordingly. Given that Direct3D works the same on gaming cards as on CAD cards, the improvements we make will apply across all graphics HW for Direct3D.
Thanks,
Norbert
Norbert Jeske
Graphics and Visualization Technology Lead
Autodesk, Inc.
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