Ever wonder why this game heats up GPU's so much?

[Betelgeuzah]

Sounds far-fetched but most likely has an effect on the performance.

If I remember correctly SC2's cutscenes had the same effect before its release so I think it's not as self-explanatory.

[Krin]

Don't be naive, where do you think the instructions come from to draw polygons ?

When you call a OpenGL or DirectX function to draw something, a machine code instruction is sent to the graphics driver. The driver sets the instruction onto the PCIe bus and then the graphics card does all the work. The time to tell the graphics card to draw something is non-existent.

CPU time is spent processing message from the server, sending messages back to the server, reading your input from your gamepad/keyboard/mouse, computing some non-exploitable elements, determining where you are and where everyone else is, and telling the graphics card what to draw. That last part is a very small amount of time in proportion to all the other things.

You're confusing "rendering" with "figuring out where stuff is". To a degree, I'd expect the "water under the city" issue to cause CPU temperature spikes, because it's still figuring out where the water is. We're not saying that it's not wasteful, but it's likely easier on the CPU to say water everywhere at sea level than to manually subtract out the calls to draw triangles from where there's land, because that's one of the primary functions of the graphics card to begin with. The water, especially since it's a texture and not really a dynamic mesh, is more responsible for how long you stare at the loading screen and a piece of the over all CPU usage profile than it is for your GPU running hot.

Games are just now beginning to off load this work into GPU's via nVidia's CUDA and the equivalent in AMD. They just haven't figured it out very well, because Graphics cards are built for Linear Algebra and matrix multiplications. Expressing some of the game's math in those terms is not trivial, by any means.