Why shaders eat graphics cards for dinner?

[hellenes]

My ancient rig:
P4 2.8 GHZ
ATI 9800 Atlantis PRO 128mb
512mb RAM
Win XP Home
When I set the SM1 I can have all settings cranked up even 4x AA,1280x1024, highest models for units, grass, textures on high etc etc...
And the game runs smooth...
However when I set the SM2 with shadows (even without shadows its still hogs the system down) Im forced to set everything on medium/low...
Is this "normal" or the game isnt optimised enough?

[caravel]

The highest shader model that your card supports is SM 2.0, and the card only has 128MB, so it may be running near it's performance limitations. SM 2.0 does come with a significant perfromance hit over SM 1.0. It's normal.

[BDC]

Looks much prettier though!

[hoom]

Its because shaders do extra maths per pixel.
Extra maths costs time/maths power.
Simple shaders do only a bit more maths than non-shaded.
But complex shaders can be doing quite complex maths for each pixel, which means they are slower but create prettier effects.

A 9800pro, while a superb card is now getting pretty long in the tooth & its not surprising that it'll have issues with new games at 1280*1024 with 4*AA.
Try dropping AA to 2* & performance should improve without too much visual impact.

[AussieGiant]

Hi guy's,

A question. Where do you go to find out the best settings for various machine set ups? Is this covered on the boards here?

[hellenes]

Its because shaders do extra maths per pixel.
Extra maths costs time/maths power.
Simple shaders do only a bit more maths than non-shaded.
But complex shaders can be doing quite complex maths for each pixel, which means they are slower but create prettier effects.

A 9800pro, while a superb card is now getting pretty long in the tooth & its not surprising that it'll have issues with new games at 1280*1024 with 4*AA.
Try dropping AA to 2* & performance should improve without too much visual impact.

But I have lag on SM2 without ANY AA at 1024x748 (lowest res IIRC)....
Its the shadows that hit the performance and the SM1 the difference is huge when I set the game to SM1 Its like I upgrade my card instantly...x4 AA 1280x1024...Anisotropic filtering x6...
BTW What does the texture filtering do? Cause I havent seen any difference...

[hoom]

Right so clearly the 9800 just doesn't have the grunt to handle the SM2 shaders which do more maths per pixel than the SM1.
At least presumably "do more maths" since doing the same maths as SM1 in SM2 should be faster.

If SM2 is actually just doing the same thing as SM1, then something may actually be broken...

AF is for the textures, ever noticed how textures in the distance/that you are looking at nearly flat to get all blurry? AF reduces that.