To restate this clearly: if implemented via a shader, double-sided surfaces on a GeForce are exactly as fast as on a Quadro using fixed-function OpenGL, they are 13 times slower.īut that’s surely an accident, right? Double-sided surfaces are extremely uncommon in the GeForce’s target applications, so Nvidia simply wouldn’t have spent any effort optimizing that code path, right? But that would only explain a 2x penalty, which would come from the laziest most backwards implementation, i.e., rendering everything twice (I actually thought about implementing that via a geometry shader, if the more direct approach hadn’t worked). I created a double-sided surface shader to go from a 13x penalty to a 2x penalty (remember, twice as many calculations), but I got only a 1.1-1.3 penalty, depending on overdraw. I didn’t believe this myself, or expected it.
Suddenly, the GeForce is just as fast as the Quadro. However, if an application implements the exact same formulas used for double-sided lighting by fixed-function OpenGL in a shader program, the difference evaporates.
NVIDIA QUADRO K600 VS QUADRO 600 SOFTWARE
That’s how legacy CAD software would do it.
Turns out, there isn’t.ĭouble-sided surfaces are slow when rendered in the “standard” OpenGL way, i.e., by enabling glLightModeli(GL_LIGHT_MODEL_TWO_SIDE,GL_TRUE). So where does the ginormous factor of 13 come from? There must be some feature specific to the GeForce’s hardware that makes double-sided surfaces slow. That would obviously take about twice as long. One way of simulating double-sided surfaces is to render single-sided surfaces twice, with triangle orientations and normal vectors flipped. What makes even less sense is that double-sided surfaces were a factor of 13 slower than single-sided surfaces (remember the claimed 10x Quadro speed-up I mentioned above?). That makes no sense, since everything else was significantly faster on a 480. Isosurfaces that rendered on the 285 at a sprightly 60 or so FPS, rendered on the 480 at a sluggish 15 FPS. Then an external user upgraded to a GeForce 480, and the bottom fell out. On a GeForce 285, 3D Visualizer’s isosurfaces ran perfectly OK. Makes sense as well on special “professional” silicon, the two lighting calculations would be run in parallel.īut a couple of years ago, I got a rude awakening. On a Quadro, the performance difference used to be, and still is, negligible. Makes sense, considering that OpenGL’s lighting engine has to do twice the amount of work. I don’t recall exactly, but the difference was significant but not outrageous, say a factor of 2-3. From way back, on a piddly GeForce 3, I know that frame rate drops precipitously when enabling double-sided surfaces (for those who don’t know: double-sided surfaces are not backface-culled, and are illuminated from both sides, often with different material properties on either side). Well, I don’t have a CAD application at hand, but I have 3D Visualizer, which uses double-sided surfaces to render contour- or iso-surfaces in 3D volumetric data. Could it be that these two features were specifically targeted for crippling in the GeForce driver, because they are so common to “workstation” applications, and so rarely used in games, to justify the Quadro’s price tags? No, right? What’s common in CAD? Wireframe rendering and double-sided surfaces. But wait: the quoted performance difference is for “professional” or “workstation” applications. So, is the Quadro a lot faster than the GeForce? According to web lore, it is, by a large factor of 10x or so (oh how I wish I could find a link to a benchmark right now, but please read on). Granted, the Quadro 6000 has 6GB of video RAM to the GeForce’s 2GB, but that doesn’t explain the difference. So, why are professional-level cards so much more expensive? For comparison, an “entry-level” $700 Quadro 4000 is significantly slower than a $530 high-end GeForce GTX 680, at least according to my measurements using several Vrui applications, and the closest performance-equivalent to a GeForce GTX 680 I could find was a Quadro 6000 for a whopping $3660. What are their differences? Obviously, gamer-level cards are cheap, because the companies face stiff competition from each other, and want to sell as many of them as possible to make a profit. There are gamer-level cards, and professional-level cards.
One of the mysteries of the modern age is the existence of two distinct lines of graphics cards by the two big manufacturers, Nvidia and ATI/AMD.
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