I'm not sure if the title is clear but with more words what I want to say is: I'm building a PC for a decorator who's main work is to render photorealistic images of house interiors. For that she uses 3dsMax and AutoCAD with Accurender and Photoshop.
Is there a need for professional graphics card like Quadro series or FireGL series? Do these cards offer any improvements on rendering time or are they only used for real time rendering?
Pro cards are usually slightly declocked versus gaming counterparts, and their drivers updated less often, since the drivers have to go through a more extensive verification process. The performance difference is fairly small but measurable, but since correct results matter more than a few seconds off of a one minute render, this is accepted.
The pro cards (and most importantly, their drivers) are guaranteed by the application software vendors to work with their application, and provide verifiable results (CAD), and/or with correct color matching (Publishing). Pro cards (and their supporting applications and drivers) provide the capability to calibrate colors, which is usually a functionality that is skipped or glossed over for the gaming cards.
While the gaming equivalents usually work fine, the exact answer to your question of need is more a matter of correctness than high performance. Whether a gaming card substitute works correctly is a question best answered by either the application vendor or the power users of that software (and its different add-ons and modules).
Things change fast, and I'm probably behind the times... I hope I am only slightly wrong with what I say.
For the most part, high end cards a great at rendering in the style of OpenGl or DirectX - scan line conversion, with vertex shaders and all that, and do so very well at high frame rates. High quality photo-real rendering usually involves ray tracing, photon mapping, Metropolis algorithms and other techniques that don't translate well into hardware, and rarely can be done real time (w/o spending big, big bucks). The high end card may pay for itself during the modeling and lighting phase, where the user interactively alters meshes, moves lights, applies textures etc. while the final output render would be done in mostly in software. Typically, a designer spends a lot of time modeling and texturing and adjusting the view, and (at least on a good day) taps the "render" button only once.
The essential stupendous point: be clear, when deciding on a graphics card, on understanding whether it's benefit is for during interactive scene design, or for the final renders.
The hardware in 'professional' graphics cards like Nvidia's Quadro range is not significantly different to that in gaming cards; the differences are really just deliberate segmentation. In some cases you could even flash certain models of GeForce with the firmware images from the corresponding Quadro model. This would enable quadro-specific features such as multiple OpenGL windows.
Typical reasons to buy a professional graphics card are:
The drivers are tested and certified to run with professional applications such as 3DS. This means that the vendors are (in theory at least) on the hook to fix driver bugs that break the applications. Graphics card vendors will typically publish a list of such certifications on their web site.
In your case this is probably the only really compelling reason to go with a pro card.
Pro graphics cards sometimes come with more memory then their consumer equivalents, particularly in the high end.
Pro cards often have better OpenGL support. For example, at one point the firmware in GeForce cards was crippled so it only allowed one OpenGL window at a time.
Sometimes features such as colour correction are not supported or are disabled on consumer parts.
In some cases the pro models support colour spaces with more than 24 bits where this feature is typically not available or disabled on consumer products.
You may not have a choice. Certain cards may be required to qualify for vendor support. For instance branded hardware like HP XW8xxx/9xxx or Z series workstations often comes with this type of card and the vendor will only provide support in specific configurations, and with branded cards they supply.
In some cases entry level pro models are the best option for multi-monitor support - particularly on low profile desktops. Low-profile consumer parts tend to be entry level cards with mixed outputs (HDMI, VGA, DVI). Low-profile Quadro (for example) cards often have DMS-59, multiple HDMI or proprietary connectors supporting up to 4 displays; similar specifications can be seen in corresponding products from ATI.
Photo realistic rendering is a processor intensive activity. The process will be sped up if the application can offload some (or all) of this activity onto the graphics card's GPU.
The better the card the better the photo-realistic rendering and real-time rendering performance.
So obviously a higher end card will improve performance. However, you probably don't need to go all the way to a professional card - a gaming card will probably do. Ultimately the difference between the two is one of degree. The professional card will have faster memory (for example).
Have you looked on the Accurender and Photoshop sites for benchmark figures and recommended machine specifications?
It's one of those cases where you need to try before you buy, but with computer hardware that's not always easy.
